# kalc

kalc is a small functional programming language that (gasp) borrows a lot of its syntax from the Excel formula language.

## ikalc

kalc comes with its own repl, known as `ikalc`. Start it up in your console by typing in `ikalc`

## Syntax

kalc is a tiny language, and it has very little syntax. It supports functions, variable assignment, arithmetic, and some string parsing functionality.

## Numbers

All numbers are floating point.

``````1 => 1.0
2.020 => 2.02
1.23E => 12300000000.0
``````

## Arithmetic

``````1 + 1 / (10 * 100) - 3 + 3 - (3 - 2)
SUM(1, 2, 3, 4, 5)
``````

Arithmetic is standard infix with nesting via parenthesis.

## Logical operations

``````2 < 1 ? 1 : 3 # Ternary
(1 || 2) # 1.0
2 or 3 # 2.0
OR(1 > 2, 3 < 2, 8 == 8) # true
``````

## Variable assignment

The assignment operator `:=` is borrowed from Pascal. This decision was made for practical reason. Since comparison operators are both `=` and `==` and the language is expression-based, `=` could not be chosen.

Variables come in a lot of different flavors.

You have standard variables:

``````a := 1 b := 2 d := a + b

d := 100.0
``````

and you have quoted variables:

``````'a' := 1 'b' := 2 'd' := 'a' + 'b'
``````

Quoted variables can contain pretty much any character that you can think of:

``````'Hello world' := 1
'Hello 2 the world' := 1
'This \' is a \' [string]' := 1
'!@#\$%^& !@#\$%^& *&^%\$%^&*' := 1
``````

The only real rule is that you need to escape a standard single quote.

## Functions

You can create functions in kalc:

``````DEFINE FOO(a, b) { a + b }
``````

You can also call functions in kalc:

``````\> a = FOO(2, 3) \> a 5
``````

There are a few examples of functions in `lib/stdlib.kalc`

## Built-in functions

There are some built-in functions (in `lib/kalc/interpreter.rb`). They are based on the Excel formula functions, so you should see some overlap.

Some of them are:

``````# Conditional
IF, OR, NOT, AND

# Random number generation
RAND

# System level integration
SYSTEM

# Boolean functions
ISLOGICAL, ISNONTEXT, ISNUMBER, ISTEXT

# Math functions
ABS, DEGREES, PRODUCT, RADIANS, ROUND, SUM, TRUNC, LN, ACOS,
ACOSH, ASIN, ASINH, ATAN, ATANH, CBRT, COS, COSH, ERF, ERFC, EXP, GAMMA,
LGAMMA, LOG, LOG2, LOG10, SIN, SINH, SQRT, TAN, TANH

# String functions
CHOMP, CHOP, CHR, CLEAR, COUNT, DOWNCASE, HEX, INSPECT, INTERN, TO_SYM, LENGTH, SIZE,
LSTRIP, SUCC, NEXT, OCT, ORD, REVERSE, RSTRIP, STRIP, SWAPCASE, TO_C,
TO_F, TO_I, TO_R, UPCASE, CHAR, CLEAN, CODE, CONCATENATE, DOLLAR, EXACT,
FIND, FIXED, LEFT, LEN, LOWER, MID, PROPER, REPLACE, REPT, RIGHT,
SEARCH, SUBSTITUTE, TRIM, UPPER, VALUE

# Regular expression functions
REGEXP_MATCH, REGEXP_REPLACE

# Debugging
P, PP, PUTS,

# Other
PLUS_ONE, MINUS_ONE, SQUARE, CUBE, FIB, FACTORIAL,
TOWERS_OF_HANOI
``````

## Loops

There are no looping mechanisms to speak of, but recursion works (pretty) well.
Note: go too deep and you might blow the stack!

``````DEFINE SAMPLE_LOOP(a) {
PUTS(a)
IF(a == 1, 1, SAMPLE_LOOP(a - 1))
}
``````

There are a few examples of loops via recursion in `lib/stdlib.kalc`

## Weirdness

And here is where it gets a bit weird. It has to look a bit like Excel, so you can expect things to look odd in places.

For example, here is how you compare 2 variables:

``````# Assign '1' to 'a' and '2' to 'b' a := 1 b := 2

# Does 'a' equal 'b'? a = b \> false

# Also, you can do this: a == b \> false

(a == a) && (b = b) \> true
``````

`=` and `==` are both equality operators. Use `:=` for assignment.

## More inside

Not everything is documented yet. As you can see, it is a mix of a lot of different ideas. The goal is to have an excel-like language that is somewhat functional.

## Contributing

Fork on GitHub and after you've committed tested patches, send a pull request.