README.md

while-lang

A small Parser and Interpreter for the Educational WHILE - Programming Language by Uwe Schoening.

Installation

Install the latest Version with pip

pip install while-lang

Using the CLI

After a successful installation you can use the whilelang script.

whilelang pathto/prog.while 1 2

where 1 and 2 are the inputs for x1 and x2 respectively.

Use -h for help.

usage: whilelang [-h] [-p] [-i] file [x1] [x2]

WHILE lang interpreter.

positional arguments:
  file              The File containing the Program
  x1                First argument.
  x2                Second argument.

optional arguments:
  -h, --help        show this help message and exit
  -p, --parse-only  Only parse the file without running. Useful for testing if the file format is correct.
  -i                Run in interpret mode. (Don't JIT Compile the While Code)

Syntax:

File -> [SubroutineDef]* Program 

SubroutineDef -> DEFINE RoutineName AS Program END

Program -> (Assign | AssignSub | Add | Sub | While) | Program ; Program
Assign -> Var := Integer
Add -> Var := Var + Integer
Sub -> Var := Var - Integer
While -> WHILE Var DO Program END
AssignSub -> Var := RoutineName ( Var , Var )

RoutineName ->  [A-Za-z_][A-Za-z0-9_]*
Var -> x0 | x1 | x2 | [a-z][A-Za-z0-9_]*

Comments can be made using #.

Example

Multiplies two numbers with subroutines.

# Define a Subroutine
DEFINE M AS
x0 := x1 - 1
END

# Calculate x1 times x2
x0 := 0;
WHILE x1 DO
    ctr := x2 + 0;
    WHILE ctr DO
     x0 := x0 + 1;
     ctr := M(ctr,ctr) # decrement the counter
    END;
    x1 := M(x1,x1)
END

Take a look at the examples folder for more examples.