Tiny BASIC - Tiny BASIC Grammar

Tiny BASIC Grammar

The grammar is listed below in Backus-Naur form. In the listing, an asterisk ("*") denotes zero or more of the object to its left — except for the first asterisk in the definition of "term", which is the multiplication operator; parentheses group objects; and an epsilon ("ε") signifies the empty set. As is common in computer language grammar notation, the vertical bar ("|") distinguishes alternatives, as does their being listed on separate lines. The symbol "CR" denotes a carriage return (usually generated by a keyboard's "Enter" key).

line ::= number statement CR | statement CR statement ::= PRINT expr-list IF expression relop expression THEN statement GOTO expression INPUT var-list LET var = expression GOSUB expression RETURN CLEAR LIST RUN END expr-list ::= (string|expression) (, (string|expression) )* var-list ::= var (, var)* expression ::= (+|-|ε) term ((+|-) term)* term ::= factor ((*|/) factor)* factor ::= var | number | (expression) var ::= A | B | C .... | Y | Z number ::= digit digit* digit ::= 0 | 1 | 2 | 3 | ... | 8 | 9 relop ::= < (>|=|ε) | > (<|=|ε) | = A BREAK from the console will interrupt execution of the program

Source: Dr. Dobb's Journal of Computer Calisthenics & Orthodontia, Volume 1, Number 1, 1976, p.9.