Module: Enumerable

Included in:
Array, Dir, Enumerator, Hash, IO, Range, String, Struct
Defined in:
enum.c

Defined Under Namespace

Classes: Enumerator

Instance Method Summary collapse

Instance Method Details

#all? {|obj| ... } ⇒ Boolean

Passes each element of the collection to the given block. The method returns true if the block never returns false or nil. If the block is not given, Ruby adds an implicit block of {|obj| obj} (that is all? will return true only if none of the collection members are false or nil.)

%w{ ant bear cat}.all? {|word| word.length >= 3}   #=> true
%w{ ant bear cat}.all? {|word| word.length >= 4}   #=> false
[ nil, true, 99 ].all?                             #=> false

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.all? [{|obj| block } ]   => true or false
 *
 *  Passes each element of the collection to the given block. The method
 *  returns <code>true</code> if the block never returns
 *  <code>false</code> or <code>nil</code>. If the block is not given,
 *  Ruby adds an implicit block of <code>{|obj| obj}</code> (that is
 *  <code>all?</code> will return <code>true</code> only if none of the
 *  collection members are <code>false</code> or <code>nil</code>.)
 *
 *     %w{ ant bear cat}.all? {|word| word.length >= 3}   #=> true
 *     %w{ ant bear cat}.all? {|word| word.length >= 4}   #=> false
 *     [ nil, true, 99 ].all?                             #=> false
 *
 */

static VALUE
enum_all(obj)
    VALUE obj;
{
    VALUE result = Qtrue;

    rb_iterate(rb_each, obj, rb_block_given_p() ? all_iter_i : all_i, (VALUE)&result);
    return result;
}

#any? {|obj| ... } ⇒ Boolean

Passes each element of the collection to the given block. The method returns true if the block ever returns a value other than false or nil. If the block is not given, Ruby adds an implicit block of {|obj| obj} (that is any? will return true if at least one of the collection members is not false or nil.

%w{ ant bear cat}.any? {|word| word.length >= 3}   #=> true
%w{ ant bear cat}.any? {|word| word.length >= 4}   #=> true
[ nil, true, 99 ].any?                             #=> true

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.any? [{|obj| block } ]   => true or false
 *
 *  Passes each element of the collection to the given block. The method
 *  returns <code>true</code> if the block ever returns a value other
 *  than <code>false</code> or <code>nil</code>. If the block is not
 *  given, Ruby adds an implicit block of <code>{|obj| obj}</code> (that
 *  is <code>any?</code> will return <code>true</code> if at least one
 *  of the collection members is not <code>false</code> or
 *  <code>nil</code>.
 *
 *     %w{ ant bear cat}.any? {|word| word.length >= 3}   #=> true
 *     %w{ ant bear cat}.any? {|word| word.length >= 4}   #=> true
 *     [ nil, true, 99 ].any?                             #=> true
 *
 */

static VALUE
enum_any(obj)
    VALUE obj;
{
    VALUE result = Qfalse;

    rb_iterate(rb_each, obj, rb_block_given_p() ? any_iter_i : any_i, (VALUE)&result);
    return result;
}

#collect {|obj| ... } ⇒ Array #map {|obj| ... } ⇒ Array

Returns a new array with the results of running block once for every element in enum.

(1..4).collect {|i| i*i }   #=> [1, 4, 9, 16]
(1..4).collect { "cat"  }   #=> ["cat", "cat", "cat", "cat"]

Overloads:

  • #collect {|obj| ... } ⇒ Array

    Yields:

    • (obj)
  • #map {|obj| ... } ⇒ Array

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.collect {| obj | block }  => array
 *     enum.map     {| obj | block }  => array
 *
 *  Returns a new array with the results of running <em>block</em> once
 *  for every element in <i>enum</i>.
 *
 *     (1..4).collect {|i| i*i }   #=> [1, 4, 9, 16]
 *     (1..4).collect { "cat"  }   #=> ["cat", "cat", "cat", "cat"]
 *
 */

static VALUE
enum_collect(obj)
    VALUE obj;
{
    VALUE ary = rb_ary_new();

    rb_iterate(rb_each, obj, rb_block_given_p() ? collect_i : collect_all, ary);

    return ary;
}

#countInteger #count(item) ⇒ Integer #count {|obj| ... } ⇒ Integer

Returns the number of items in enum, where #size is called if it responds to it, otherwise the items are counted through enumeration. If an argument is given, counts the number of items in enum, for which equals to item. If a block is given, counts the number of elements yielding a true value.

ary = [1, 2, 4, 2]
ary.count             # => 4
ary.count(2)          # => 2
ary.count{|x|x%2==0}  # => 3

Overloads:

  • #count {|obj| ... } ⇒ Integer

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.count                   => int
 *     enum.count(item)             => int
 *     enum.count {| obj | block }  => int
 *
 *  Returns the number of items in <i>enum</i>, where #size is called
 *  if it responds to it, otherwise the items are counted through
 *  enumeration.  If an argument is given, counts the number of items
 *  in <i>enum</i>, for which equals to <i>item</i>.  If a block is
 *  given, counts the number of elements yielding a true value.
 *
 *     ary = [1, 2, 4, 2]
 *     ary.count             # => 4
 *     ary.count(2)          # => 2
 *     ary.count{|x|x%2==0}  # => 3
 *
 */

static VALUE
enum_count(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE memo[2];  /* [count, condition value] */
    rb_block_call_func *func;

    if (argc == 0) {
    if (rb_block_given_p()) {
        func = count_iter_i;
    }
    else {
        if (rb_respond_to(obj, id_size)) {
        return rb_funcall(obj, id_size, 0, 0);
        }
        func = count_all_i;
    }
    }
    else {
    rb_scan_args(argc, argv, "1", &memo[1]);
    if (rb_block_given_p()) {
        rb_warn("given block not used");
    }
        func = count_i;
    }

    memo[0] = 0;
    rb_block_call(obj, id_each, 0, 0, func, (VALUE)&memo);
    return INT2NUM(memo[0]);
}

#cycle {|obj| ... } ⇒ Object #cycle(n) {|obj| ... } ⇒ Object

Calls block for each element of enum repeatedly n times or forever if none or nil is given. If a non-positive number is given or the collection is empty, does nothing. Returns nil if the loop has finished without getting interrupted.

Enumerable#cycle saves elements in an internal array so changes to enum after the first pass have no effect.

a = ["a", "b", "c"]
a.cycle {|x| puts x }  # print, a, b, c, a, b, c,.. forever.
a.cycle(2) {|x| puts x }  # print, a, b, c, a, b, c.

Overloads:

  • #cycle {|obj| ... } ⇒ Object

    Yields:

    • (obj)
  • #cycle(n) {|obj| ... } ⇒ Object

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.cycle {|obj| block }
 *     enum.cycle(n) {|obj| block }
 *
 *  Calls <i>block</i> for each element of <i>enum</i> repeatedly _n_
 *  times or forever if none or nil is given.  If a non-positive
 *  number is given or the collection is empty, does nothing.  Returns
 *  nil if the loop has finished without getting interrupted.
 *
 *  Enumerable#cycle saves elements in an internal array so changes
 *  to <i>enum</i> after the first pass have no effect.
 *
 *     a = ["a", "b", "c"]
 *     a.cycle {|x| puts x }  # print, a, b, c, a, b, c,.. forever.
 *     a.cycle(2) {|x| puts x }  # print, a, b, c, a, b, c.
 *
 */

static VALUE
enum_cycle(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE ary;
    VALUE nv = Qnil;
    long n, i, len;

    rb_scan_args(argc, argv, "01", &nv);

    RETURN_ENUMERATOR(obj, argc, argv);
    if (NIL_P(nv)) {
        n = -1;
    }
    else {
        n = NUM2LONG(nv);
        if (n <= 0) return Qnil;
    }
    ary = rb_ary_new();
    RBASIC(ary)->klass = 0;
    rb_block_call(obj, id_each, 0, 0, cycle_i, ary);
    len = RARRAY(ary)->len;
    if (len == 0) return Qnil;
    while (n < 0 || 0 < --n) {
        for (i=0; i<len; i++) {
            rb_yield(RARRAY(ary)->ptr[i]);
        }
    }
    return Qnil;        /* not reached */
}

#detect(ifnone = nil) {|obj| ... } ⇒ Object? #find(ifnone = nil) {|obj| ... } ⇒ Object?

Passes each entry in enum to block. Returns the first for which block is not false. If no object matches, calls ifnone and returns its result when it is specified, or returns nil

(1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35

Overloads:

  • #detect(ifnone = nil) {|obj| ... } ⇒ Object?

    Yields:

    • (obj)
  • #find(ifnone = nil) {|obj| ... } ⇒ Object?

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.detect(ifnone = nil) {| obj | block }  => obj or nil
 *     enum.find(ifnone = nil)   {| obj | block }  => obj or nil
 *
 *  Passes each entry in <i>enum</i> to <em>block</em>. Returns the
 *  first for which <em>block</em> is not <code>false</code>.  If no
 *  object matches, calls <i>ifnone</i> and returns its result when it
 *  is specified, or returns <code>nil</code>
 *
 *     (1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
 *     (1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35
 *
 */

static VALUE
enum_find(argc, argv, obj)
    int argc;
    VALUE* argv;
    VALUE obj;
{
    VALUE memo = Qundef;
    VALUE if_none;

    rb_scan_args(argc, argv, "01", &if_none);
    RETURN_ENUMERATOR(obj, argc, argv);
    rb_iterate(rb_each, obj, find_i, (VALUE)&memo);
    if (memo != Qundef) {
    return memo;
    }
    if (!NIL_P(if_none)) {
    return rb_funcall(if_none, rb_intern("call"), 0, 0);
    }
    return Qnil;
}

#drop(n) ⇒ Array

Drops first n elements from enum, and returns rest elements in an array.

a = [1, 2, 3, 4, 5, 0]
a.drop(3)             # => [4, 5, 0]


# File 'enum.c'

/*
 *  call-seq:
 *     enum.drop(n)               => array
 *
 *  Drops first n elements from <i>enum</i>, and returns rest elements
 *  in an array.
 *
 *     a = [1, 2, 3, 4, 5, 0]
 *     a.drop(3)             # => [4, 5, 0]
 *
 */

static VALUE
enum_drop(obj, n)
    VALUE obj;
    VALUE n;
{
    VALUE args[2];
    long len = NUM2LONG(n);

    if (len < 0) {
    rb_raise(rb_eArgError, "attempt to drop negative size");
    }

    args[1] = len;
    args[0] = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, drop_i, (VALUE)args);
    return args[0];
}

#drop_while {|arr| ... } ⇒ Array

Drops elements up to, but not including, the first element for which the block returns nil or false and returns an array containing the remaining elements.

a = [1, 2, 3, 4, 5, 0]
a.drop_while {|i| i < 3 }   # => [3, 4, 5, 0]

Yields:

  • (arr)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.drop_while {|arr| block }   => array
 *
 *  Drops elements up to, but not including, the first element for
 *  which the block returns nil or false and returns an array
 *  containing the remaining elements.
 *
 *     a = [1, 2, 3, 4, 5, 0]
 *     a.drop_while {|i| i < 3 }   # => [3, 4, 5, 0]
 *
 */

static VALUE
enum_drop_while(obj)
    VALUE obj;
{
    VALUE args[2];

    RETURN_ENUMERATOR(obj, 0, 0);
    args[0] = rb_ary_new();
    args[1] = Qfalse;
    rb_block_call(obj, id_each, 0, 0, drop_while_i, (VALUE)args);
    return args[0];
}

#each_cons(n) { ... } ⇒ Object #each_cons(n) ⇒ Object

Iterates the given block for each array of consecutive <n> elements. If no block is given, returns an enumerator.a

e.g.:

(1..10).each_cons(3) {|a| p a}
# outputs below
[1, 2, 3]
[2, 3, 4]
[3, 4, 5]
[4, 5, 6]
[5, 6, 7]
[6, 7, 8]
[7, 8, 9]
[8, 9, 10]

Overloads:

  • #each_cons(n) { ... } ⇒ Object

    Yields:



# File 'enumerator.c'

/*
 *  call-seq:
 *    each_cons(n) {...}
 *    each_cons(n)
 *
 *  Iterates the given block for each array of consecutive <n>
 *  elements.  If no block is given, returns an enumerator.a
 *
 *  e.g.:
 *      (1..10).each_cons(3) {|a| p a}
 *      # outputs below
 *      [1, 2, 3]
 *      [2, 3, 4]
 *      [3, 4, 5]
 *      [4, 5, 6]
 *      [5, 6, 7]
 *      [6, 7, 8]
 *      [7, 8, 9]
 *      [8, 9, 10]
 *
 */
static VALUE
enum_each_cons(obj, n)
    VALUE obj, n;
{
    long size = NUM2LONG(n);
    VALUE args[2];

    if (size <= 0) rb_raise(rb_eArgError, "invalid size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_cons_i, (VALUE)args);

    return Qnil;
}

#each_slice(n) { ... } ⇒ Object #each_slice(n) ⇒ Object

Iterates the given block for each slice of <n> elements. If no block is given, returns an enumerator.

e.g.:

(1..10).each_slice(3) {|a| p a}
# outputs below
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]
[10]

Overloads:

  • #each_slice(n) { ... } ⇒ Object

    Yields:



# File 'enumerator.c'

/*
 *  call-seq:
 *    e.each_slice(n) {...}
 *    e.each_slice(n)
 *
 *  Iterates the given block for each slice of <n> elements.  If no
 *  block is given, returns an enumerator.
 *
 *  e.g.:
 *      (1..10).each_slice(3) {|a| p a}
 *      # outputs below
 *      [1, 2, 3]
 *      [4, 5, 6]
 *      [7, 8, 9]
 *      [10]
 *
 */
static VALUE
enum_each_slice(obj, n)
    VALUE obj, n;
{
    long size = NUM2LONG(n);
    VALUE args[2], ary;

    if (size <= 0) rb_raise(rb_eArgError, "invalid slice size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_slice_i, (VALUE)args);

    ary = args[0];
    if (RARRAY_LEN(ary) > 0) rb_yield(ary);

    return Qnil;
}

#each_with_index {|obj, i| ... } ⇒ Enumerator

Calls block with two arguments, the item and its index, for each item in enum.

hash = Hash.new
%w(cat dog wombat).each_with_index {|item, index|
  hash[item] = index
}
hash   #=> {"cat"=>0, "wombat"=>2, "dog"=>1}

Yields:

  • (obj, i)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.each_with_index {|obj, i| block }  -> enum
 *
 *  Calls <em>block</em> with two arguments, the item and its index, for
 *  each item in <i>enum</i>.
 *
 *     hash = Hash.new
 *     %w(cat dog wombat).each_with_index {|item, index|
 *       hash[item] = index
 *     }
 *     hash   #=> {"cat"=>0, "wombat"=>2, "dog"=>1}
 *
 */

static VALUE
enum_each_with_index(obj)
    VALUE obj;
{
    VALUE memo;

    RETURN_ENUMERATOR(obj, 0, 0);

    memo = 0;
    rb_iterate(rb_each, obj, each_with_index_i, (VALUE)&memo);
    return obj;
}

#to_aArray #entriesArray

Returns an array containing the items in enum.

(1..7).to_a                       #=> [1, 2, 3, 4, 5, 6, 7]
{ 'a'=>1, 'b'=>2, 'c'=>3 }.to_a   #=> [["a", 1], ["b", 2], ["c", 3]]


# File 'enum.c'

/*
 *  call-seq:
 *     enum.to_a      =>    array
 *     enum.entries   =>    array
 *
 *  Returns an array containing the items in <i>enum</i>.
 *
 *     (1..7).to_a                       #=> [1, 2, 3, 4, 5, 6, 7]
 *     { 'a'=>1, 'b'=>2, 'c'=>3 }.to_a   #=> [["a", 1], ["b", 2], ["c", 3]]
 */
static VALUE
enum_to_a(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE ary = rb_ary_new();

    rb_block_call(obj, id_each, argc, argv, collect_all, ary);

    return ary;
}

#each_cons(n) { ... } ⇒ Object #each_cons(n) ⇒ Object

Iterates the given block for each array of consecutive <n> elements. If no block is given, returns an enumerator.a

e.g.:

(1..10).each_cons(3) {|a| p a}
# outputs below
[1, 2, 3]
[2, 3, 4]
[3, 4, 5]
[4, 5, 6]
[5, 6, 7]
[6, 7, 8]
[7, 8, 9]
[8, 9, 10]

Overloads:

  • #each_cons(n) { ... } ⇒ Object

    Yields:



# File 'enumerator.c'

/*
 *  call-seq:
 *    each_cons(n) {...}
 *    each_cons(n)
 *
 *  Iterates the given block for each array of consecutive <n>
 *  elements.  If no block is given, returns an enumerator.a
 *
 *  e.g.:
 *      (1..10).each_cons(3) {|a| p a}
 *      # outputs below
 *      [1, 2, 3]
 *      [2, 3, 4]
 *      [3, 4, 5]
 *      [4, 5, 6]
 *      [5, 6, 7]
 *      [6, 7, 8]
 *      [7, 8, 9]
 *      [8, 9, 10]
 *
 */
static VALUE
enum_each_cons(obj, n)
    VALUE obj, n;
{
    long size = NUM2LONG(n);
    VALUE args[2];

    if (size <= 0) rb_raise(rb_eArgError, "invalid size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_cons_i, (VALUE)args);

    return Qnil;
}

#each_slice(n) { ... } ⇒ Object #each_slice(n) ⇒ Object

Iterates the given block for each slice of <n> elements. If no block is given, returns an enumerator.

e.g.:

(1..10).each_slice(3) {|a| p a}
# outputs below
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]
[10]

Overloads:

  • #each_slice(n) { ... } ⇒ Object

    Yields:



# File 'enumerator.c'

/*
 *  call-seq:
 *    e.each_slice(n) {...}
 *    e.each_slice(n)
 *
 *  Iterates the given block for each slice of <n> elements.  If no
 *  block is given, returns an enumerator.
 *
 *  e.g.:
 *      (1..10).each_slice(3) {|a| p a}
 *      # outputs below
 *      [1, 2, 3]
 *      [4, 5, 6]
 *      [7, 8, 9]
 *      [10]
 *
 */
static VALUE
enum_each_slice(obj, n)
    VALUE obj, n;
{
    long size = NUM2LONG(n);
    VALUE args[2], ary;

    if (size <= 0) rb_raise(rb_eArgError, "invalid slice size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_slice_i, (VALUE)args);

    ary = args[0];
    if (RARRAY_LEN(ary) > 0) rb_yield(ary);

    return Qnil;
}

#each_with_index {|obj, i| ... } ⇒ Enumerator

Calls block with two arguments, the item and its index, for each item in enum.

hash = Hash.new
%w(cat dog wombat).each_with_index {|item, index|
  hash[item] = index
}
hash   #=> {"cat"=>0, "wombat"=>2, "dog"=>1}

Yields:

  • (obj, i)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.each_with_index {|obj, i| block }  -> enum
 *
 *  Calls <em>block</em> with two arguments, the item and its index, for
 *  each item in <i>enum</i>.
 *
 *     hash = Hash.new
 *     %w(cat dog wombat).each_with_index {|item, index|
 *       hash[item] = index
 *     }
 *     hash   #=> {"cat"=>0, "wombat"=>2, "dog"=>1}
 *
 */

static VALUE
enum_each_with_index(obj)
    VALUE obj;
{
    VALUE memo;

    RETURN_ENUMERATOR(obj, 0, 0);

    memo = 0;
    rb_iterate(rb_each, obj, each_with_index_i, (VALUE)&memo);
    return obj;
}

#detect(ifnone = nil) {|obj| ... } ⇒ Object? #find(ifnone = nil) {|obj| ... } ⇒ Object?

Passes each entry in enum to block. Returns the first for which block is not false. If no object matches, calls ifnone and returns its result when it is specified, or returns nil

(1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35

Overloads:

  • #detect(ifnone = nil) {|obj| ... } ⇒ Object?

    Yields:

    • (obj)
  • #find(ifnone = nil) {|obj| ... } ⇒ Object?

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.detect(ifnone = nil) {| obj | block }  => obj or nil
 *     enum.find(ifnone = nil)   {| obj | block }  => obj or nil
 *
 *  Passes each entry in <i>enum</i> to <em>block</em>. Returns the
 *  first for which <em>block</em> is not <code>false</code>.  If no
 *  object matches, calls <i>ifnone</i> and returns its result when it
 *  is specified, or returns <code>nil</code>
 *
 *     (1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
 *     (1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35
 *
 */

static VALUE
enum_find(argc, argv, obj)
    int argc;
    VALUE* argv;
    VALUE obj;
{
    VALUE memo = Qundef;
    VALUE if_none;

    rb_scan_args(argc, argv, "01", &if_none);
    RETURN_ENUMERATOR(obj, argc, argv);
    rb_iterate(rb_each, obj, find_i, (VALUE)&memo);
    if (memo != Qundef) {
    return memo;
    }
    if (!NIL_P(if_none)) {
    return rb_funcall(if_none, rb_intern("call"), 0, 0);
    }
    return Qnil;
}

#find_all {|obj| ... } ⇒ Array #select {|obj| ... } ⇒ Array

Returns an array containing all elements of enum for which block is not false (see also Enumerable#reject).

(1..10).find_all {|i|  i % 3 == 0 }   #=> [3, 6, 9]

Overloads:

  • #find_all {|obj| ... } ⇒ Array

    Yields:

    • (obj)
  • #select {|obj| ... } ⇒ Array

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.find_all {| obj | block }  => array
 *     enum.select   {| obj | block }  => array
 *
 *  Returns an array containing all elements of <i>enum</i> for which
 *  <em>block</em> is not <code>false</code> (see also
 *  <code>Enumerable#reject</code>).
 *
 *     (1..10).find_all {|i|  i % 3 == 0 }   #=> [3, 6, 9]
 *
 */

static VALUE
enum_find_all(obj)
    VALUE obj;
{
    VALUE ary = rb_ary_new();

    RETURN_ENUMERATOR(obj, 0, 0);
    rb_iterate(rb_each, obj, find_all_i, ary);

    return ary;
}

#find_index(value) ⇒ Integer? #find_index {|obj| ... } ⇒ Integer?

Compares each entry in enum with value or passes to block. Returns the index for the first for which the evaluated value is non-false. If no object matches, returns nil

(1..10).find_index  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..100).find_index {|i| i % 5 == 0 and i % 7 == 0 }   #=> 34
(1..100).find_index(50)                                #=> 49

Overloads:

  • #find_index {|obj| ... } ⇒ Integer?

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.find_index(value)            => int or nil
 *     enum.find_index {| obj | block }  => int or nil
 *
 *  Compares each entry in <i>enum</i> with <em>value</em> or passes
 *  to <em>block</em>.  Returns the index for the first for which the
 *  evaluated value is non-false.  If no object matches, returns
 *  <code>nil</code>
 *
 *     (1..10).find_index  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
 *     (1..100).find_index {|i| i % 5 == 0 and i % 7 == 0 }   #=> 34
 *     (1..100).find_index(50)                                #=> 49
 *
 */

static VALUE
enum_find_index(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE memo[3];  /* [return value, current index, condition value] */
    rb_block_call_func *func;

    if (argc == 0) {
        RETURN_ENUMERATOR(obj, 0, 0);
        func = find_index_iter_i;
    }
    else {
    rb_scan_args(argc, argv, "1", &memo[2]);
    if (rb_block_given_p()) {
        rb_warn("given block not used");
    }
        func = find_index_i;
    }

    memo[0] = Qnil;
    memo[1] = 0;
    rb_block_call(obj, id_each, 0, 0, func, (VALUE)memo);
    return memo[0];
}

#firstObject? #first(n) ⇒ Array

Returns the first element, or the first n elements, of the enumerable. If the enumerable is empty, the first form returns nil, and the second form returns an empty array.



# File 'enum.c'

/*
 *  call-seq:
 *     enum.first      -> obj or nil
 *     enum.first(n)   -> an_array
 *
 *  Returns the first element, or the first +n+ elements, of the enumerable.
 *  If the enumerable is empty, the first form returns <code>nil</code>, and the
 *  second form returns an empty array.
 *
 */

static VALUE
enum_first(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE n, ary[2];

    if (argc == 0) {
    ary[0] = ary[1] = Qnil;
    }
    else {
    long len;
    rb_scan_args(argc, argv, "01", &n);
    len = NUM2LONG(n);
    if (len == 0) return rb_ary_new2(0);
    ary[0] = INT2NUM(len);
    ary[1] = rb_ary_new2(len);
    }
    rb_block_call(obj, id_each, 0, 0, first_i, (VALUE)ary);

    return ary[1];
}

#grep(pattern) ⇒ Array #grep(pattern) {|obj| ... } ⇒ Array

Returns an array of every element in enum for which Pattern === element. If the optional block is supplied, each matching element is passed to it, and the block's result is stored in the output array.

(1..100).grep 38..44   #=> [38, 39, 40, 41, 42, 43, 44]
c = IO.constants
c.grep(/SEEK/)         #=> ["SEEK_END", "SEEK_SET", "SEEK_CUR"]
res = c.grep(/SEEK/) {|v| IO.const_get(v) }
res                    #=> [2, 0, 1]

Overloads:

  • #grep(pattern) {|obj| ... } ⇒ Array

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.grep(pattern)                   => array
 *     enum.grep(pattern) {| obj | block }  => array
 *
 *  Returns an array of every element in <i>enum</i> for which
 *  <code>Pattern === element</code>. If the optional <em>block</em> is
 *  supplied, each matching element is passed to it, and the block's
 *  result is stored in the output array.
 *
 *     (1..100).grep 38..44   #=> [38, 39, 40, 41, 42, 43, 44]
 *     c = IO.constants
 *     c.grep(/SEEK/)         #=> ["SEEK_END", "SEEK_SET", "SEEK_CUR"]
 *     res = c.grep(/SEEK/) {|v| IO.const_get(v) }
 *     res                    #=> [2, 0, 1]
 *
 */

static VALUE
enum_grep(obj, pat)
    VALUE obj, pat;
{
    VALUE ary = rb_ary_new();
    VALUE arg[2];

    arg[0] = pat;
    arg[1] = ary;

    rb_iterate(rb_each, obj, rb_block_given_p() ? grep_iter_i : grep_i, (VALUE)arg);

    return ary;
}

#group_by {|obj| ... } ⇒ Hash

Returns a hash, which keys are evaluated result from the block, and values are arrays of elements in enum corresponding to the key.

(1..6).group_by {|i| i%3}   #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.group_by {| obj | block }  => a_hash
 *
 *  Returns a hash, which keys are evaluated result from the
 *  block, and values are arrays of elements in <i>enum</i>
 *  corresponding to the key.
 *
 *     (1..6).group_by {|i| i%3}   #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}
 *
 */

static VALUE
enum_group_by(obj)
    VALUE obj;
{
    VALUE hash;

    RETURN_ENUMERATOR(obj, 0, 0);

    hash = rb_hash_new();
    rb_block_call(obj, id_each, 0, 0, group_by_i, hash);

    return hash;
}

#include?(obj) ⇒ Boolean #member?(obj) ⇒ Boolean

Returns true if any member of enum equals obj. Equality is tested using ==.

IO.constants.include? "SEEK_SET"          #=> true
IO.constants.include? "SEEK_NO_FURTHER"   #=> false


# File 'enum.c'

/*
 *  call-seq:
 *     enum.include?(obj)     => true or false
 *     enum.member?(obj)      => true or false
 *
 *  Returns <code>true</code> if any member of <i>enum</i> equals
 *  <i>obj</i>. Equality is tested using <code>==</code>.
 *
 *     IO.constants.include? "SEEK_SET"          #=> true
 *     IO.constants.include? "SEEK_NO_FURTHER"   #=> false
 *
 */

static VALUE
enum_member(obj, val)
    VALUE obj, val;
{
    VALUE memo[2];

    memo[0] = val;
    memo[1] = Qfalse;
    rb_iterate(rb_each, obj, member_i, (VALUE)memo);
    return memo[1];
}

#inject(initial, sym) ⇒ Object #inject(sym) ⇒ Object #inject(initial) {|memo, obj| ... } ⇒ Object #inject {|memo, obj| ... } ⇒ Object

enum.reduce(initial, sym) => obj

enum.reduce(sym)          => obj
enum.reduce(initial) {| memo, obj | block }  => obj
enum.reduce          {| memo, obj | block }  => obj

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator.

If you specify a block, then for each element in enum<i> the block is passed an accumulator value (<i>memo) and the element. If you specify a symbol instead, then each element in the collection will be passed to the named method of memo. In either case, the result becomes the new value for memo. At the end of the iteration, the final value of memo is the return value fo the method.

If you do not explicitly specify an initial value for memo, then uses the first element of collection is used as the initial value of memo.

Examples:

# Sum some numbers
(5..10).reduce(:+)                            #=> 45
# Same using a block and inject
(5..10).inject {|sum, n| sum + n }            #=> 45
# Multiply some numbers
(5..10).reduce(1, :*)                         #=> 151200
# Same using a block
(5..10).inject(1) {|product, n| product * n } #=> 151200
# find the longest word
longest = %w{ cat sheep bear }.inject do |memo,word|
   memo.length > word.length ? memo : word
end
longest                                       #=> "sheep"

Overloads:

  • #inject(initial) {|memo, obj| ... } ⇒ Object

    Yields:

    • (memo, obj)
  • #inject {|memo, obj| ... } ⇒ Object

    Yields:

    • (memo, obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.inject(initial, sym) => obj
 *     enum.inject(sym)          => obj
 *     enum.inject(initial) {| memo, obj | block }  => obj
 *     enum.inject          {| memo, obj | block }  => obj
 *
 *     enum.reduce(initial, sym) => obj
 *     enum.reduce(sym)          => obj
 *     enum.reduce(initial) {| memo, obj | block }  => obj
 *     enum.reduce          {| memo, obj | block }  => obj
 *
 *  Combines all elements of <i>enum</i> by applying a binary
 *  operation, specified by a block or a symbol that names a
 *  method or operator.
 *
 *  If you specify a block, then for each element in <i>enum<i>
 *  the block is passed an accumulator value (<i>memo</i>) and the element.
 *  If you specify a symbol instead, then each element in the collection
 *  will be passed to the named method of <i>memo</i>.
 *  In either case, the result becomes the new value for <i>memo</i>.
 *  At the end of the iteration, the final value of <i>memo</i> is the
 *  return value fo the method.
 *
 *  If you do not explicitly specify an <i>initial</i> value for <i>memo</i>,
 *  then uses the first element of collection is used as the initial value
 *  of <i>memo</i>.
 *
 *  Examples:
 *
 *     # Sum some numbers
 *     (5..10).reduce(:+)                            #=> 45
 *     # Same using a block and inject
 *     (5..10).inject {|sum, n| sum + n }            #=> 45
 *     # Multiply some numbers
 *     (5..10).reduce(1, :*)                         #=> 151200
 *     # Same using a block
 *     (5..10).inject(1) {|product, n| product * n } #=> 151200
 *     # find the longest word
 *     longest = %w{ cat sheep bear }.inject do |memo,word|
 *        memo.length > word.length ? memo : word
 *     end
 *     longest                                       #=> "sheep"
 *
 */
static VALUE
enum_inject(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE memo[2];
    rb_block_call_func *iter = inject_i;

    switch (rb_scan_args(argc, argv, "02", &memo[0], &memo[1])) {
      case 0:
    memo[0] = Qundef;
    break;
      case 1:
    if (rb_block_given_p()) {
        break;
    }
    memo[1] = (VALUE)rb_to_id(memo[0]);
    memo[0] = Qundef;
    iter = inject_op_i;
    break;
      case 2:
    if (rb_block_given_p()) {
        rb_warning("given block not used");
    }
    memo[1] = (VALUE)rb_to_id(memo[1]);
    iter = inject_op_i;
    break;
    }
    rb_block_call(obj, id_each, 0, 0, iter, (VALUE)memo);
    if (memo[0] == Qundef) return Qnil;
    return memo[0];
}

#collect {|obj| ... } ⇒ Array #map {|obj| ... } ⇒ Array

Returns a new array with the results of running block once for every element in enum.

(1..4).collect {|i| i*i }   #=> [1, 4, 9, 16]
(1..4).collect { "cat"  }   #=> ["cat", "cat", "cat", "cat"]

Overloads:

  • #collect {|obj| ... } ⇒ Array

    Yields:

    • (obj)
  • #map {|obj| ... } ⇒ Array

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.collect {| obj | block }  => array
 *     enum.map     {| obj | block }  => array
 *
 *  Returns a new array with the results of running <em>block</em> once
 *  for every element in <i>enum</i>.
 *
 *     (1..4).collect {|i| i*i }   #=> [1, 4, 9, 16]
 *     (1..4).collect { "cat"  }   #=> ["cat", "cat", "cat", "cat"]
 *
 */

static VALUE
enum_collect(obj)
    VALUE obj;
{
    VALUE ary = rb_ary_new();

    rb_iterate(rb_each, obj, rb_block_given_p() ? collect_i : collect_all, ary);

    return ary;
}

#maxObject #max {|a, b| ... } ⇒ Object

Returns the object in enum with the maximum value. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

a = %w(albatross dog horse)
a.max                                  #=> "horse"
a.max {|a,b| a.length <=> b.length }   #=> "albatross"

Overloads:

  • #max {|a, b| ... } ⇒ Object

    Yields:

    • (a, b)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.max                   => obj
 *     enum.max {|a,b| block }    => obj
 *
 *  Returns the object in _enum_ with the maximum value. The
 *  first form assumes all objects implement <code>Comparable</code>;
 *  the second uses the block to return <em>a <=> b</em>.
 *
 *     a = %w(albatross dog horse)
 *     a.max                                  #=> "horse"
 *     a.max {|a,b| a.length <=> b.length }   #=> "albatross"
 */

static VALUE
enum_max(obj)
    VALUE obj;
{
    VALUE result = Qundef;

    rb_iterate(rb_each, obj, rb_block_given_p() ? max_ii : max_i, (VALUE)&result);
    if (result == Qundef) return Qnil;
    return result;
}

#max_by {|obj| ... } ⇒ Object

Returns the object in enum that gives the maximum value from the given block.

a = %w(albatross dog horse)
a.max_by {|x| x.length }   #=> "albatross"

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.max_by {| obj| block }   => obj
 *
 *  Returns the object in <i>enum</i> that gives the maximum
 *  value from the given block.
 *
 *     a = %w(albatross dog horse)
 *     a.max_by {|x| x.length }   #=> "albatross"
 */

static VALUE
enum_max_by(obj)
    VALUE obj;
{
    VALUE memo[2];

    RETURN_ENUMERATOR(obj, 0, 0);

    memo[0] = Qundef;
    memo[1] = Qnil;
    rb_block_call(obj, id_each, 0, 0, max_by_i, (VALUE)memo);
    return memo[1];
}

#include?(obj) ⇒ Boolean #member?(obj) ⇒ Boolean

Returns true if any member of enum equals obj. Equality is tested using ==.

IO.constants.include? "SEEK_SET"          #=> true
IO.constants.include? "SEEK_NO_FURTHER"   #=> false


# File 'enum.c'

/*
 *  call-seq:
 *     enum.include?(obj)     => true or false
 *     enum.member?(obj)      => true or false
 *
 *  Returns <code>true</code> if any member of <i>enum</i> equals
 *  <i>obj</i>. Equality is tested using <code>==</code>.
 *
 *     IO.constants.include? "SEEK_SET"          #=> true
 *     IO.constants.include? "SEEK_NO_FURTHER"   #=> false
 *
 */

static VALUE
enum_member(obj, val)
    VALUE obj, val;
{
    VALUE memo[2];

    memo[0] = val;
    memo[1] = Qfalse;
    rb_iterate(rb_each, obj, member_i, (VALUE)memo);
    return memo[1];
}

#minObject #min {|a, b| ... } ⇒ Object

Returns the object in enum with the minimum value. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

a = %w(albatross dog horse)
a.min                                  #=> "albatross"
a.min {|a,b| a.length <=> b.length }   #=> "dog"

Overloads:

  • #min {|a, b| ... } ⇒ Object

    Yields:

    • (a, b)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.min                    => obj
 *     enum.min {| a,b | block }   => obj
 *
 *  Returns the object in <i>enum</i> with the minimum value. The
 *  first form assumes all objects implement <code>Comparable</code>;
 *  the second uses the block to return <em>a <=> b</em>.
 *
 *     a = %w(albatross dog horse)
 *     a.min                                  #=> "albatross"
 *     a.min {|a,b| a.length <=> b.length }   #=> "dog"
 */

static VALUE
enum_min(obj)
    VALUE obj;
{
    VALUE result = Qundef;

    rb_iterate(rb_each, obj, rb_block_given_p() ? min_ii : min_i, (VALUE)&result);
    if (result == Qundef) return Qnil;
    return result;
}

#min_by {|obj| ... } ⇒ Object

Returns the object in enum that gives the minimum value from the given block.

a = %w(albatross dog horse)
a.min_by {|x| x.length }   #=> "dog"

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.min_by {| obj| block }   => obj
 *
 *  Returns the object in <i>enum</i> that gives the minimum
 *  value from the given block.
 *
 *     a = %w(albatross dog horse)
 *     a.min_by {|x| x.length }   #=> "dog"
 */

static VALUE
enum_min_by(obj)
    VALUE obj;
{
    VALUE memo[2];

    RETURN_ENUMERATOR(obj, 0, 0);

    memo[0] = Qundef;
    memo[1] = Qnil;
    rb_block_call(obj, id_each, 0, 0, min_by_i, (VALUE)memo);
    return memo[1];
}

#minmaxArray #minmax {|a, b| ... } ⇒ Array

Returns two elements array which contains the minimum and the maximum value in the enumerable. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

a = %w(albatross dog horse)
a.minmax                                  #=> ["albatross", "horse"]
a.minmax {|a,b| a.length <=> b.length }   #=> ["dog", "albatross"]

Overloads:

  • #minmax {|a, b| ... } ⇒ Array

    Yields:

    • (a, b)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.minmax                   => [min,max]
 *     enum.minmax {|a,b| block }    => [min,max]
 *
 *  Returns two elements array which contains the minimum and the
 *  maximum value in the enumerable.  The first form assumes all
 *  objects implement <code>Comparable</code>; the second uses the
 *  block to return <em>a <=> b</em>.
 *
 *     a = %w(albatross dog horse)
 *     a.minmax                                  #=> ["albatross", "horse"]
 *     a.minmax {|a,b| a.length <=> b.length }   #=> ["dog", "albatross"]
 */

static VALUE
enum_minmax(obj)
    VALUE obj;
{
    VALUE result[3];
    VALUE ary = rb_ary_new3(2, Qnil, Qnil);

    result[0] = Qundef;
    if (rb_block_given_p()) {
    result[2] = ary;
    rb_block_call(obj, id_each, 0, 0, minmax_ii, (VALUE)result);
    }
    else {
    rb_block_call(obj, id_each, 0, 0, minmax_i, (VALUE)result);
    }
    if (result[0] != Qundef) {
        RARRAY(ary)->ptr[0] = result[0];
        RARRAY(ary)->ptr[1] = result[1];
    }
    return ary;
}

#minmax_by {|obj| ... } ⇒ Array

Returns two elements array array containing the objects in enum that gives the minimum and maximum values respectively from the given block.

a = %w(albatross dog horse)
a.minmax_by {|x| x.length }   #=> ["dog", "albatross"]

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.minmax_by {| obj| block }   => [min, max]
 *
 *  Returns two elements array array containing the objects in
 *  <i>enum</i> that gives the minimum and maximum values respectively
 *  from the given block.
 *
 *     a = %w(albatross dog horse)
 *     a.minmax_by {|x| x.length }   #=> ["dog", "albatross"]
 */

static VALUE
enum_minmax_by(obj)
    VALUE obj;
{
    VALUE memo[4];

    RETURN_ENUMERATOR(obj, 0, 0);

    memo[0] = Qundef;
    memo[1] = Qundef;
    memo[2] = Qnil;
    memo[3] = Qnil;
    rb_block_call(obj, id_each, 0, 0, minmax_by_i, (VALUE)memo);
    return rb_assoc_new(memo[2], memo[3]);
}

#none? {|obj| ... } ⇒ Boolean

Passes each element of the collection to the given block. The method returns true if the block never returns true for all elements. If the block is not given, none? will return true only if none of the collection members is true.

%w{ant bear cat}.none? {|word| word.length == 5}  #=> true
%w{ant bear cat}.none? {|word| word.length >= 4}  #=> false
[].none?                                          #=> true
[nil].none?                                       #=> true
[nil,false].none?                                 #=> true

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.none? [{|obj| block }]   => true or false
 *
 *  Passes each element of the collection to the given block. The method
 *  returns <code>true</code> if the block never returns <code>true</code>
 *  for all elements. If the block is not given, <code>none?</code> will return
 *  <code>true</code> only if none of the collection members is true.
 *
 *     %w{ant bear cat}.none? {|word| word.length == 5}  #=> true
 *     %w{ant bear cat}.none? {|word| word.length >= 4}  #=> false
 *     [].none?                                          #=> true
 *     [nil].none?                                       #=> true
 *     [nil,false].none?                                 #=> true
 */
static VALUE
enum_none(obj)
    VALUE obj;
{
    VALUE result = Qtrue;

    rb_block_call(obj, id_each, 0, 0, rb_block_given_p() ? none_iter_i : none_i, (VALUE)&result);
    return result;
}

#one? {|obj| ... } ⇒ Boolean

Passes each element of the collection to the given block. The method returns true if the block returns true exactly once. If the block is not given, one? will return true only if exactly one of the collection members is true.

%w{ant bear cat}.one? {|word| word.length == 4}   #=> true
%w{ant bear cat}.one? {|word| word.length > 4}    #=> false
%w{ant bear cat}.one? {|word| word.length < 4}    #=> false
[ nil, true, 99 ].one?                            #=> false
[ nil, true, false ].one?                         #=> true

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.one? [{|obj| block }]   => true or false
 *
 *  Passes each element of the collection to the given block. The method
 *  returns <code>true</code> if the block returns <code>true</code>
 *  exactly once. If the block is not given, <code>one?</code> will return
 *  <code>true</code> only if exactly one of the collection members is
 *  true.
 *
 *     %w{ant bear cat}.one? {|word| word.length == 4}   #=> true
 *     %w{ant bear cat}.one? {|word| word.length > 4}    #=> false
 *     %w{ant bear cat}.one? {|word| word.length < 4}    #=> false
 *     [ nil, true, 99 ].one?                            #=> false
 *     [ nil, true, false ].one?                         #=> true
 *
 */

static VALUE
enum_one(obj)
    VALUE obj;
{
    VALUE result = Qundef;

    rb_block_call(obj, id_each, 0, 0, rb_block_given_p() ? one_iter_i : one_i, (VALUE)&result);
    if (result == Qundef) return Qfalse;
    return result;
}

#partition {|obj| ... } ⇒ Array

Returns two arrays, the first containing the elements of enum for which the block evaluates to true, the second containing the rest.

(1..6).partition {|i| (i&1).zero?}   #=> [[2, 4, 6], [1, 3, 5]]

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.partition {| obj | block }  => [ true_array, false_array ]
 *
 *  Returns two arrays, the first containing the elements of
 *  <i>enum</i> for which the block evaluates to true, the second
 *  containing the rest.
 *
 *     (1..6).partition {|i| (i&1).zero?}   #=> [[2, 4, 6], [1, 3, 5]]
 *
 */

static VALUE
enum_partition(obj)
    VALUE obj;
{
    VALUE ary[2];

    RETURN_ENUMERATOR(obj, 0, 0);

    ary[0] = rb_ary_new();
    ary[1] = rb_ary_new();
    rb_iterate(rb_each, obj, partition_i, (VALUE)ary);

    return rb_assoc_new(ary[0], ary[1]);
}

#inject(initial, sym) ⇒ Object #inject(sym) ⇒ Object #inject(initial) {|memo, obj| ... } ⇒ Object #inject {|memo, obj| ... } ⇒ Object

enum.reduce(initial, sym) => obj

enum.reduce(sym)          => obj
enum.reduce(initial) {| memo, obj | block }  => obj
enum.reduce          {| memo, obj | block }  => obj

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator.

If you specify a block, then for each element in enum<i> the block is passed an accumulator value (<i>memo) and the element. If you specify a symbol instead, then each element in the collection will be passed to the named method of memo. In either case, the result becomes the new value for memo. At the end of the iteration, the final value of memo is the return value fo the method.

If you do not explicitly specify an initial value for memo, then uses the first element of collection is used as the initial value of memo.

Examples:

# Sum some numbers
(5..10).reduce(:+)                            #=> 45
# Same using a block and inject
(5..10).inject {|sum, n| sum + n }            #=> 45
# Multiply some numbers
(5..10).reduce(1, :*)                         #=> 151200
# Same using a block
(5..10).inject(1) {|product, n| product * n } #=> 151200
# find the longest word
longest = %w{ cat sheep bear }.inject do |memo,word|
   memo.length > word.length ? memo : word
end
longest                                       #=> "sheep"

Overloads:

  • #inject(initial) {|memo, obj| ... } ⇒ Object

    Yields:

    • (memo, obj)
  • #inject {|memo, obj| ... } ⇒ Object

    Yields:

    • (memo, obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.inject(initial, sym) => obj
 *     enum.inject(sym)          => obj
 *     enum.inject(initial) {| memo, obj | block }  => obj
 *     enum.inject          {| memo, obj | block }  => obj
 *
 *     enum.reduce(initial, sym) => obj
 *     enum.reduce(sym)          => obj
 *     enum.reduce(initial) {| memo, obj | block }  => obj
 *     enum.reduce          {| memo, obj | block }  => obj
 *
 *  Combines all elements of <i>enum</i> by applying a binary
 *  operation, specified by a block or a symbol that names a
 *  method or operator.
 *
 *  If you specify a block, then for each element in <i>enum<i>
 *  the block is passed an accumulator value (<i>memo</i>) and the element.
 *  If you specify a symbol instead, then each element in the collection
 *  will be passed to the named method of <i>memo</i>.
 *  In either case, the result becomes the new value for <i>memo</i>.
 *  At the end of the iteration, the final value of <i>memo</i> is the
 *  return value fo the method.
 *
 *  If you do not explicitly specify an <i>initial</i> value for <i>memo</i>,
 *  then uses the first element of collection is used as the initial value
 *  of <i>memo</i>.
 *
 *  Examples:
 *
 *     # Sum some numbers
 *     (5..10).reduce(:+)                            #=> 45
 *     # Same using a block and inject
 *     (5..10).inject {|sum, n| sum + n }            #=> 45
 *     # Multiply some numbers
 *     (5..10).reduce(1, :*)                         #=> 151200
 *     # Same using a block
 *     (5..10).inject(1) {|product, n| product * n } #=> 151200
 *     # find the longest word
 *     longest = %w{ cat sheep bear }.inject do |memo,word|
 *        memo.length > word.length ? memo : word
 *     end
 *     longest                                       #=> "sheep"
 *
 */
static VALUE
enum_inject(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE memo[2];
    rb_block_call_func *iter = inject_i;

    switch (rb_scan_args(argc, argv, "02", &memo[0], &memo[1])) {
      case 0:
    memo[0] = Qundef;
    break;
      case 1:
    if (rb_block_given_p()) {
        break;
    }
    memo[1] = (VALUE)rb_to_id(memo[0]);
    memo[0] = Qundef;
    iter = inject_op_i;
    break;
      case 2:
    if (rb_block_given_p()) {
        rb_warning("given block not used");
    }
    memo[1] = (VALUE)rb_to_id(memo[1]);
    iter = inject_op_i;
    break;
    }
    rb_block_call(obj, id_each, 0, 0, iter, (VALUE)memo);
    if (memo[0] == Qundef) return Qnil;
    return memo[0];
}

#reject {|obj| ... } ⇒ Array

Returns an array for all elements of enum for which block is false (see also Enumerable#find_all).

(1..10).reject {|i|  i % 3 == 0 }   #=> [1, 2, 4, 5, 7, 8, 10]

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.reject {| obj | block }  => array
 *
 *  Returns an array for all elements of <i>enum</i> for which
 *  <em>block</em> is false (see also <code>Enumerable#find_all</code>).
 *
 *     (1..10).reject {|i|  i % 3 == 0 }   #=> [1, 2, 4, 5, 7, 8, 10]
 *
 */

static VALUE
enum_reject(obj)
    VALUE obj;
{
    VALUE ary = rb_ary_new();

    RETURN_ENUMERATOR(obj, 0, 0);
    rb_iterate(rb_each, obj, reject_i, ary);

    return ary;
}

#reverse_each {|item| ... } ⇒ Object

Traverses enum in reverse order.

Yields:

  • (item)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.reverse_each {|item| block } 
 *  
 *  Traverses <i>enum</i> in reverse order.
 */

static VALUE
enum_reverse_each(int argc, VALUE *argv, VALUE obj)
{
    VALUE ary;
    long i;

    RETURN_ENUMERATOR(obj, argc, argv);

    ary = enum_to_a(argc, argv, obj);

    for (i = RARRAY_LEN(ary); --i >= 0; ) {
    rb_yield(RARRAY_PTR(ary)[i]);
    }

    return obj;
}

#find_all {|obj| ... } ⇒ Array #select {|obj| ... } ⇒ Array

Returns an array containing all elements of enum for which block is not false (see also Enumerable#reject).

(1..10).find_all {|i|  i % 3 == 0 }   #=> [3, 6, 9]

Overloads:

  • #find_all {|obj| ... } ⇒ Array

    Yields:

    • (obj)
  • #select {|obj| ... } ⇒ Array

    Yields:

    • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.find_all {| obj | block }  => array
 *     enum.select   {| obj | block }  => array
 *
 *  Returns an array containing all elements of <i>enum</i> for which
 *  <em>block</em> is not <code>false</code> (see also
 *  <code>Enumerable#reject</code>).
 *
 *     (1..10).find_all {|i|  i % 3 == 0 }   #=> [3, 6, 9]
 *
 */

static VALUE
enum_find_all(obj)
    VALUE obj;
{
    VALUE ary = rb_ary_new();

    RETURN_ENUMERATOR(obj, 0, 0);
    rb_iterate(rb_each, obj, find_all_i, ary);

    return ary;
}

#sortArray #sort {|a, b| ... } ⇒ Array

Returns an array containing the items in enum sorted, either according to their own <=> method, or by using the results of the supplied block. The block should return -1, 0, or +1 depending on the comparison between a and b. As of Ruby 1.8, the method Enumerable#sort_by implements a built-in Schwartzian Transform, useful when key computation or comparison is expensive..

%w(rhea kea flea).sort         #=> ["flea", "kea", "rhea"]
(1..10).sort {|a,b| b <=> a}   #=> [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]

Overloads:

  • #sort {|a, b| ... } ⇒ Array

    Yields:

    • (a, b)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.sort                     => array
 *     enum.sort {| a, b | block }   => array
 *
 *  Returns an array containing the items in <i>enum</i> sorted,
 *  either according to their own <code><=></code> method, or by using
 *  the results of the supplied block. The block should return -1, 0, or
 *  +1 depending on the comparison between <i>a</i> and <i>b</i>. As of
 *  Ruby 1.8, the method <code>Enumerable#sort_by</code> implements a
 *  built-in Schwartzian Transform, useful when key computation or
 *  comparison is expensive..
 *
 *     %w(rhea kea flea).sort         #=> ["flea", "kea", "rhea"]
 *     (1..10).sort {|a,b| b <=> a}   #=> [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
 */

static VALUE
enum_sort(obj)
    VALUE obj;
{
    return rb_ary_sort(enum_to_a(0, 0, obj));
}

#sort_by {|obj| ... } ⇒ Array

Sorts enum using a set of keys generated by mapping the values in enum through the given block.

%w{ apple pear fig }.sort_by {|word| word.length}
               #=> ["fig", "pear", "apple"]

The current implementation of sort_by generates an array of tuples containing the original collection element and the mapped value. This makes sort_by fairly expensive when the keysets are simple

require 'benchmark'
include Benchmark

a = (1..100000).map {rand(100000)}

bm(10) do |b|
  b.report("Sort")    { a.sort }
  b.report("Sort by") { a.sort_by {|a| a} }
end

produces:

user     system      total        real
Sort        0.180000   0.000000   0.180000 (  0.175469)
Sort by     1.980000   0.040000   2.020000 (  2.013586)

However, consider the case where comparing the keys is a non-trivial operation. The following code sorts some files on modification time using the basic sort method.

files = Dir["*"]
sorted = files.sort {|a,b| File.new(a).mtime <=> File.new(b).mtime}
sorted   #=> ["mon", "tues", "wed", "thurs"]

This sort is inefficient: it generates two new File objects during every comparison. A slightly better technique is to use the Kernel#test method to generate the modification times directly.

files = Dir["*"]
sorted = files.sort { |a,b|
  test(?M, a) <=> test(?M, b)
}
sorted   #=> ["mon", "tues", "wed", "thurs"]

This still generates many unnecessary Time objects. A more efficient technique is to cache the sort keys (modification times in this case) before the sort. Perl users often call this approach a Schwartzian Transform, after Randal Schwartz. We construct a temporary array, where each element is an array containing our sort key along with the filename. We sort this array, and then extract the filename from the result.

sorted = Dir["*"].collect { |f|
   [test(?M, f), f]
}.sort.collect { |f| f[1] }
sorted   #=> ["mon", "tues", "wed", "thurs"]

This is exactly what sort_by does internally.

sorted = Dir["*"].sort_by {|f| test(?M, f)}
sorted   #=> ["mon", "tues", "wed", "thurs"]

Yields:

  • (obj)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.sort_by {| obj | block }    => array
 *
 *  Sorts <i>enum</i> using a set of keys generated by mapping the
 *  values in <i>enum</i> through the given block.
 *
 *     %w{ apple pear fig }.sort_by {|word| word.length}
                    #=> ["fig", "pear", "apple"]
 *
 *  The current implementation of <code>sort_by</code> generates an
 *  array of tuples containing the original collection element and the
 *  mapped value. This makes <code>sort_by</code> fairly expensive when
 *  the keysets are simple
 *
 *     require 'benchmark'
 *     include Benchmark
 *
 *     a = (1..100000).map {rand(100000)}
 *
 *     bm(10) do |b|
 *       b.report("Sort")    { a.sort }
 *       b.report("Sort by") { a.sort_by {|a| a} }
 *     end
 *
 *  <em>produces:</em>
 *
 *     user     system      total        real
 *     Sort        0.180000   0.000000   0.180000 (  0.175469)
 *     Sort by     1.980000   0.040000   2.020000 (  2.013586)
 *
 *  However, consider the case where comparing the keys is a non-trivial
 *  operation. The following code sorts some files on modification time
 *  using the basic <code>sort</code> method.
 *
 *     files = Dir["*"]
 *     sorted = files.sort {|a,b| File.new(a).mtime <=> File.new(b).mtime}
 *     sorted   #=> ["mon", "tues", "wed", "thurs"]
 *
 *  This sort is inefficient: it generates two new <code>File</code>
 *  objects during every comparison. A slightly better technique is to
 *  use the <code>Kernel#test</code> method to generate the modification
 *  times directly.
 *
 *     files = Dir["*"]
 *     sorted = files.sort { |a,b|
 *       test(?M, a) <=> test(?M, b)
 *     }
 *     sorted   #=> ["mon", "tues", "wed", "thurs"]
 *
 *  This still generates many unnecessary <code>Time</code> objects. A
 *  more efficient technique is to cache the sort keys (modification
 *  times in this case) before the sort. Perl users often call this
 *  approach a Schwartzian Transform, after Randal Schwartz. We
 *  construct a temporary array, where each element is an array
 *  containing our sort key along with the filename. We sort this array,
 *  and then extract the filename from the result.
 *
 *     sorted = Dir["*"].collect { |f|
 *        [test(?M, f), f]
 *     }.sort.collect { |f| f[1] }
 *     sorted   #=> ["mon", "tues", "wed", "thurs"]
 *
 *  This is exactly what <code>sort_by</code> does internally.
 *
 *     sorted = Dir["*"].sort_by {|f| test(?M, f)}
 *     sorted   #=> ["mon", "tues", "wed", "thurs"]
 */

static VALUE
enum_sort_by(obj)
    VALUE obj;
{
    VALUE ary;
    long i;

    RETURN_ENUMERATOR(obj, 0, 0);

    if (TYPE(obj) == T_ARRAY) {
    ary  = rb_ary_new2(RARRAY(obj)->len);
    }
    else {
    ary = rb_ary_new();
    }
    RBASIC(ary)->klass = 0;
    rb_iterate(rb_each, obj, sort_by_i, ary);
    if (RARRAY(ary)->len > 1) {
    qsort(RARRAY(ary)->ptr, RARRAY(ary)->len, sizeof(VALUE),
          sort_by_cmp, (void *)ary);
    }
    if (RBASIC(ary)->klass) {
    rb_raise(rb_eRuntimeError, "sort_by reentered");
    }
    for (i=0; i<RARRAY(ary)->len; i++) {
    RARRAY(ary)->ptr[i] = RNODE(RARRAY(ary)->ptr[i])->u2.value;
    }
    RBASIC(ary)->klass = rb_cArray;
    return ary;
}

#take(n) ⇒ Array

Returns first n elements from enum.

a = [1, 2, 3, 4, 5, 0]
a.take(3)             # => [1, 2, 3]


# File 'enum.c'

/*
 *  call-seq:
 *     enum.take(n)               => array
 *
 *  Returns first n elements from <i>enum</i>.
 *
 *     a = [1, 2, 3, 4, 5, 0]
 *     a.take(3)             # => [1, 2, 3]
 *
 */

static VALUE
enum_take(obj, n)
    VALUE obj;
    VALUE n;
{
    VALUE args[2];
    long len = NUM2LONG(n);

    if (len < 0) {
    rb_raise(rb_eArgError, "attempt to take negative size");
    }

    if (len == 0) return rb_ary_new2(0);
    args[1] = len;
    args[0] = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, take_i, (VALUE)args);
    return args[0];
}

#take_while {|arr| ... } ⇒ Array

Passes elements to the block until the block returns nil or false, then stops iterating and returns an array of all prior elements.

a = [1, 2, 3, 4, 5, 0]
a.take_while {|i| i < 3 }   # => [1, 2]

Yields:

  • (arr)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.take_while {|arr| block }   => array
 *
 *  Passes elements to the block until the block returns nil or false,
 *  then stops iterating and returns an array of all prior elements.
 *
 *     a = [1, 2, 3, 4, 5, 0]
 *     a.take_while {|i| i < 3 }   # => [1, 2]
 *
 */

static VALUE
enum_take_while(obj)
    VALUE obj;
{
    VALUE ary;

    RETURN_ENUMERATOR(obj, 0, 0);
    ary = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, take_while_i, (VALUE)&ary);
    return ary;
}

#to_aArray #entriesArray

Returns an array containing the items in enum.

(1..7).to_a                       #=> [1, 2, 3, 4, 5, 6, 7]
{ 'a'=>1, 'b'=>2, 'c'=>3 }.to_a   #=> [["a", 1], ["b", 2], ["c", 3]]


# File 'enum.c'

/*
 *  call-seq:
 *     enum.to_a      =>    array
 *     enum.entries   =>    array
 *
 *  Returns an array containing the items in <i>enum</i>.
 *
 *     (1..7).to_a                       #=> [1, 2, 3, 4, 5, 6, 7]
 *     { 'a'=>1, 'b'=>2, 'c'=>3 }.to_a   #=> [["a", 1], ["b", 2], ["c", 3]]
 */
static VALUE
enum_to_a(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE ary = rb_ary_new();

    rb_block_call(obj, id_each, argc, argv, collect_all, ary);

    return ary;
}

#zip(arg, ...) ⇒ Array #zip(arg, ...) {|arr| ... } ⇒ nil

Converts any arguments to arrays, then merges elements of enum with corresponding elements from each argument. This generates a sequence of enum#size n-element arrays, where n is one more that the count of arguments. If the size of any argument is less than enum#size, nil values are supplied. If a block given, it is invoked for each output array, otherwise an array of arrays is returned.

a = [ 4, 5, 6 ]
b = [ 7, 8, 9 ]

(1..3).zip(a, b)      #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
"cat\ndog".zip([1])   #=> [["cat\n", 1], ["dog", nil]]
(1..3).zip            #=> [[1], [2], [3]]

Overloads:

  • #zip(arg, ...) {|arr| ... } ⇒ nil

    Yields:

    • (arr)


# File 'enum.c'

/*
 *  call-seq:
 *     enum.zip(arg, ...)                   => array
 *     enum.zip(arg, ...) {|arr| block }    => nil
 *
 *  Converts any arguments to arrays, then merges elements of
 *  <i>enum</i> with corresponding elements from each argument. This
 *  generates a sequence of <code>enum#size</code> <em>n</em>-element
 *  arrays, where <em>n</em> is one more that the count of arguments. If
 *  the size of any argument is less than <code>enum#size</code>,
 *  <code>nil</code> values are supplied. If a block given, it is
 *  invoked for each output array, otherwise an array of arrays is
 *  returned.
 *
 *     a = [ 4, 5, 6 ]
 *     b = [ 7, 8, 9 ]
 *
 *     (1..3).zip(a, b)      #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
 *     "cat\ndog".zip([1])   #=> [["cat\n", 1], ["dog", nil]]
 *     (1..3).zip            #=> [[1], [2], [3]]
 *
 */

static VALUE
enum_zip(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    int i;
    VALUE result;
    VALUE memo[3];

    for (i=0; i<argc; i++) {
    argv[i] = rb_convert_type(argv[i], T_ARRAY, "Array", "to_a");
    }
    result = rb_block_given_p() ? Qnil : rb_ary_new();
    memo[0] = result;
    memo[1] = rb_ary_new4(argc, argv);
    memo[2] = 0;
    rb_iterate(rb_each, obj, zip_i, (VALUE)memo);

    return result;
}