A small math shell with a simple function plot support.

I wrote it to learn Python3.

$... = parameter [...] = optional parameter

• var $name $expression --> define a variable with the value of expression
• func $name $definition --> define a function
• plot $function [A=-10] [B=10] --> plot a function
• exit [expression] --> close the program
• print [expression] --> print an expression
• message [string] --> print an expression literal message
• read --> read an expression from standard input
• vread $name --> read a variable from standard input
• fread $name --> read a function from standard input
• exec $file --> open a file and execute it
• help --> show help