rpn.cr

A RPN parser and executor written in crystal. It can parse RPN from both infix and RPN strings, and execute RPN to find a result.

Currently it supports + - * / and ^ (exponent) operators.

Installation

Add this to your application's shard.yml:

dependencies:
  rpn:
    github: RX14/rpn.cr
    version: 0.1.0

require "rpn"

Execute RPN given as an array of numbers and symbols

RPN.execute([0.5, 2, :"*", 4 :"+"]) # => 5.0

Parse RPN from a string containing RPN notation

RPN.from_string("-.5 2 * 4 +") # => [-0.5, 2.0, :"*", 4.0, :"+"]

Parse RPN from a string containing infix notation

RPN.from_infix("4 + (5 - 3)^4 * 2") # => [4.0, 5.0, 3.0, :"-", 4.0, :"^", 2.0, :"*", :"+"]

There are shortcut methods for executing strings directly.

RPN.execute_string("3 4 +")
# Same as
RPN.execute(RPN.from_string("3 4 +"))

RPN.execute_infix("3 + 4")
# Same as
RPN.execute(RPN.from_infix("3 + 4"))

Hack around, then crystal spec.