andrewchambers / janet-big

A simple big integer library for janet

big

A big calculator library for janet. Currently only big integers are supported (no floating point).

Janet-big supports

• conversion to big/int from Janet numbers, strings, int/u64 and int/s64
• conversion to string from big/int (using string function)
• The basic Janet math operators: +, -, *, /, %, mod, band, bor, bxor, where at least one operand is a big/int, and the other may be big/int or number or int/u64 or int/s64.
• comparison operations (between big/ints) and
• polymorphic comparison (big/int vs Janet numbers and int/u64 int/s64, but not vs strings). This means predicates from the core like even? odd? zero? pos? neg? and one? should work correctly.
• includes big/pow (exponentiation), big/sqrt (integer square root), and big/divmod (quotient and remainder returned as a tuple. These functions also accept numbers, big/ints, or int/u64,int/s64 as arguments.
• Note -- other numeric functions in the Janet core, like the math/ will generally not work with big/ints.
• Note -- of the functions and methods within: only big/int accepts strings as arguments and converts to big/int. The other functions/methods will generally coerce arguments to big/int as needed, but only from Janet numbers, int/u64, int/s64.

Install

jpm install

Quick Usage

(import big)

(+ (big/int "999999999999999999999999999999999999999999") 1)

# forward and reverse addition and multiplication
(assert (= (string (+ (big/int 1) (big/int "2") 3)) "6"))
(assert (= (string (+ 1 (big/int 1))) "2"))
(assert (= (big/int 8) (* (big/int 4) 2)))
(assert (= (big/int 77) (* 11 (big/int 7))))

# test that you can create a big/int from string, number, int/s64 int/u64
(assert (= (big/int "77") (big/int 77) (big/int (int/s64 77)) (big/int (int/u64 77))))
(assert (= (big/int -77) (big/int (int/s64 -77))))

# supports polymorphic comparison
(assert (= -1 (compare (big/int 7) 8)))
(assert (= 0 (compare (big/int 7) 7)))
(assert (= 1 (compare (big/int 7) 6)))

# power and sqrt
(assert (= (big/pow 234 567) (product (seq [:repeat 567] (big/int 234)))))
(assert (= (big/sqrt (big/int "12345678987654321234567890987654321")) (big/int "111111111000000001")))
(assert (deep= (tuple (big/int "4764666551245775863") (big/int 708)) (big/divmod (big/int "23456453431782954574257") (big/int 4923))))

See many more examples in test/big.janet