Parse EBNF: Difference between revisions

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 =={{header|PicoLisp}}==
+<lang PicoLisp>(de EBNF
-{{improve|PicoLisp|The input description should be EBNF, not a parsed form of it.}}
-<lang PicoLisp>(def 'expr   'ebnf  '(term ((PLUS | MINUS) term) *))
+   "expr  : term ( ( PLUS | MINUS )  term )* ;"
-(def 'term   'ebnf  '(factor ((MULT | DIV) factor) *))
+   "term  : factor ( ( MULT | DIV ) factor )* ;"
-(def 'factor 'ebnf  '(NUMBER))</lang>
+   "factor   : NUMBER ;" )
+(for E EBNF
+   (use (@S @E)
+      (unless (and (match '(@S : @E ;) (str E)) (not (cdr @S)))
+         (quit "Invalid EBNF" E) )
+      (put (car @S) 'ebnf @E) ) )</lang>
 <lang PicoLisp>(de matchEbnf (Pat)
    (cond