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Haskell Calc

Version 1.0 (with Parsec)

Build Instructions

The build process has been automated using cabal. This allows for building of the executable in a few easy steps. Move to the HaskellCalc directory and enter the following into the terminal:

  1. cabal configure
  2. cabal build

The executable is created within a folder called dist. To clean up run cabal clean

What

Haskell Calc is a calculator written in haskell which can be interacted with via the command line. It supports:

  • Standard Arithmetic Operations: addition, subtraction, multiplication and division.
  • Boolean Operations: Not, And and Or
  • Relational Operations: Less than, Greater than and Equal to
  • Simple scripting including : conditionals, looping and functions

How

The interface supports a number of statement types:

Prompt Interaction

  • quit will exit the calculator prompt
  • help will display this README file
  • load adr will load the file found at the relative address adr and evaluate its contents
  • ! n will reevaluate the nth statement in history (The statement number is displayed in the prompt)

Script Statements

  • print(e) will evaluate and display the arithmetic or boolean expression
  • if (e) then {stmt1} else {stmt2} will evaluate e and then run the corresponding stmt (braces and brackets are optional)
  • while (e) then {stmt} will repeatedly run the stmt until the expression evaluates to false (braces and brackets are optional)
  • defun NAME (COMMA,SEPERATED,ARGUMENT,NAMES) {stmt} will store the stmt as an executable function (braces are optional, brackets are NOT)
  • NAME(COMMA,SEPARATED,EXPRS) will execute the function with the given name, using the results from evaluating the expressions as arguments (if more arguments are supplied than originally declared in function definition, the additional variables are ignored)

Expression Syntax

Expressions are whitespace insensitive (for arithmetic), have the expected precedence rules and are left associative. There are two prefix operators:

  • Boolean Not which is written "not"
  • The arithmetic negativity operator "-" To apply these operators multiple times brackets must be used i.e, -(-2) = 2 but --2 is undefined

All other operators are binary. These are listed below:

  • Arithmetic: +, -, *, /
  • Boolean: and, or
  • Relational: <, =, >