Method: Enumerable#sum

Defined in:

enum.c

#sum(initial_value = 0) ⇒ Numeric #sum(initial_value = 0) {|element| ... } ⇒ Object

With no block given, returns the sum of initial_value and the elements:

(1..100).sum          # => 5050
(1..100).sum(1)       # => 5051
('a'..'d').sum('foo') # => "fooabcd"

Generally, the sum is computed using methods + and each; for performance optimizations, those methods may not be used, and so any redefinition of those methods may not have effect here.

One such optimization: When possible, computes using Gauss’s summation formula n(n+1)/2:

100 * (100 + 1) / 2 # => 5050

With a block given, calls the block with each element; returns the sum of initial_value and the block return values:

(1..4).sum {|i| i*i }                        # => 30
(1..4).sum(100) {|i| i*i }                   # => 130
h = {a: 0, b: 1, c: 2, d: 3, e: 4, f: 5}
h.sum {|key, value| value.odd? ? value : 0 } # => 9
('a'..'f').sum('x') {|c| c < 'd' ? c : '' }  # => "xabc"

Overloads:

• #sum(initial_value = 0) ⇒ Numeric

  Returns:

  • (Numeric)
• #sum(initial_value = 0) {|element| ... } ⇒ Object

  Yields:

  • (element)

  Returns:

  • (Object)

# File 'enum.c', line 4806

static VALUE
enum_sum(int argc, VALUE* argv, VALUE obj)
{
    struct enum_sum_memo memo;
    VALUE beg, end;
    int excl;

    memo.v = (rb_check_arity(argc, 0, 1) == 0) ? LONG2FIX(0) : argv[0];
    memo.block_given = rb_block_given_p();
    memo.n = 0;
    memo.r = Qundef;

    if ((memo.float_value = RB_FLOAT_TYPE_P(memo.v))) {
        memo.f = RFLOAT_VALUE(memo.v);
        memo.c = 0.0;
    }
    else {
        memo.f = 0.0;
        memo.c = 0.0;
    }

    if (RTEST(rb_range_values(obj, &beg, &end, &excl))) {
        if (!memo.block_given && !memo.float_value &&
                (FIXNUM_P(beg) || RB_BIGNUM_TYPE_P(beg)) &&
                (FIXNUM_P(end) || RB_BIGNUM_TYPE_P(end))) {
            return int_range_sum(beg, end, excl, memo.v);
        }
    }

    if (RB_TYPE_P(obj, T_HASH) &&
            rb_method_basic_definition_p(CLASS_OF(obj), id_each))
        hash_sum(obj, &memo);
    else
        rb_block_call(obj, id_each, 0, 0, enum_sum_i, (VALUE)&memo);

    if (memo.float_value) {
        return DBL2NUM(memo.f + memo.c);
    }
    else {
        if (memo.n != 0)
            memo.v = rb_fix_plus(LONG2FIX(memo.n), memo.v);
        if (!UNDEF_P(memo.r)) {
            memo.v = rb_rational_plus(memo.r, memo.v);
        }
        return memo.v;
    }
}