Lispcalc

A Lisp-like calculator interpreter written in Ruby.

Inspired by Clojure and my Casio fx-85GT CW calculator, this library provides an interpreter that allows you to perform mathematical calculations using Lisp syntax. It uses Ruby's BigDecimal for all calculations, so it supports very accurate floating point numbers.

gem install lispcalc

This library is intended to be used via the eval method.

Here are some examples:

irb(main):001> require 'lispcalc'
=> true
irb(main):002> Lispcalc.eval('(+ 1 2 3)')
=> 0.6e1
irb(main):003> Lispcalc.eval('(+ 1 2 3)').to_s('F')
=> "6.0"
irb(main):004> Lispcalc.eval('(+ (* 2 3) (/ 2 3))').to_s('F')
=> "6.666666666666666666666666666666666667"
irb(main):005' Lispcalc.eval('
irb(main):006'   (do
irb(main):007'     (>x 100)
irb(main):008'     (>y 200)
irb(main):009'     (*
irb(main):010'       (+ x y)
irb(main):011'       (- x y)
irb(main):012>       (/ x y)))').to_s('F')
=> "-15000.0"

• Variables: As in the fx-85GT CW calculator, there are 9 variables available: A, B, C, D, E, F, x, y and z, all of them initialized to 0. You can set any of these variables to a specific value. For example, (>A 100) will set the variable A to the value 100. You can also reference a variable's value like this: (+ A B).
• Constants: There are 2 available constants: pi and e, which hold the values of the corresponding mathematical constants. Unlike variables, you cannot change the value of a constant.
• Sequencing ((do expr1 expr2 ...)): Evaluate each expression from left to right, returning the final value.
• Arithmetic operations (+, -, *, /)
• Powers (^, sq)
• Roots (sqrt, cbrt)
• Logarithms (log, log2, log10, ln)
• Trigonometric functions (sin, cos, tan, asin, acos, atan)
• Clojure-style thread macros (->, ->>) ??

I created this library for two purposes:

1. Learning more about compilers and interpreters, and how to implement them.
2. Practising my rusty Ruby skills.

This software is released under MIT license.