basic

A simple basic interpreter.

Usage

./basic < file name >

File name should end with '.bas'.

Grammar

line ::= [number] statement [note] CR
statement ::= "PRINT" print-list
			| "INPUT" var
			| "IF" expression "THEN" statement
			| "FOR" var "=" expression "TO" expression [ "STEP" expression ] "THEN" statement
			| "NEXT"
			| var = expression
			| "GOTO" number
			| "GOSUB" number
			| "RETURN"
			| "END"
print-list	::= (string | expression) { (","|";") (string | expression) }
expression	::= addsub { (">"|"<"|"<="|">="|"<>") addsub }
addsub		::= term { ("+"|"-") term }
term		::= pow { ("*"|"/"|"%") pow }
pow 		::= factor { "^" factor }
factor		::= ["+"|"-"] ( var | number |"("expression")" )

---

var		= /[A-Z]/
number	= /[0-9]*(.[0-9]+)?e[0-9]+/
string	= /"[^"]+"/