calc-haskell

An awesome (?) calculator in Haskell.

What can I do with this?

You can do a lot of things with this piece of code:

• Show someone the worst way to parse an expression.
• Delete the code and save some space for gifs like this.
• Do some simple calculations (if you really want to).

I want to do some calculations

If you really want to do calculations then please follow the following:

First, install and run the cabal project:

git clone https://github.com/paritosh-08/calc-haskell.git
cd calc-haskell
cabal new-run

Now enter the expression that needs to be evaluated.

Expression Docs

The expression is of three types:

• Number: This is an INTEGER (only as of now) and you need to directly enter the number, eg 5 is an expression but 5.0 will give an error
• Function: There are two functions as of now:
  • sqrt: This takes an expression and returns the square root of the evaluted expression. i.e. I can write sqrt(4) and this will be evauated to 2.
  • ifzero: This function has the syntax: ifzero(<expression1> ? <expression2> : <expression3>). <expression1> is the condition that will be evaluated and checked if it is zero or not. If <expression1> turns out to be zero then, the function will return <expression2>, else it will return <expression3>.
• Binary Operations: This will always be enclosed within brackets, i.e the syntax is (<expression1> <OPERATOR> <expression2>). Here <OPERATOR> can be anything from the list: [+,-,/,*,^]. The meaning of each operator is defined below:

  Operator	Meaning	Example	Result
  +	Adds two entities	2+2	4
  -	Subtracts second entity from the first one	3-2	1
  *	Multiplies two entities	3*2	6
  /	Divides first entity by the second one	6/3	2
  ^	Raises first entity by the power of second one	2^3	8

Examples of expressions

Expression	Result	Explanation (if any)
45	45	Integers can act as an expression
(2+5)	7	This is an example of Binary Operation
((3+5)/4)	2	Binary operation where first argument is a Binary operation
ifzero(0?5:6)	5	An example of Function Expression
sqrt(16)	4	Another example of Function Expression

Errors in expression evaluation

Sometimes the programme will return Something went wrong. The error handling will be done in future, but for now, you can debug by the following steps:

• First run cabal repl.
• Now write parseTest parseExpression <EXPRESSION> and hit enter (replace <EXPRESSION> by the expression which caused some error).
• Hopefully, you will get some human readable error.
• To exit, just write :q and hit enter.

Things to keep in Mind

Please use integers only in the expression.

Always use brackets to envelope the operator expression, 2+2 will give error for sure. Instead write (2+2).