Anonymous user
Parse EBNF: Difference between revisions
Added PicoLisp
m (→{{header|Tcl}}: Note that this is not exactly what the task description calls for, but it is what it probably *should* want) |
(Added PicoLisp) |
||
Line 10:
factor : NUMBER ;</pre>
=={{header|PicoLisp}}==
<lang PicoLisp>(de parse (Str)
(let *L (str Str "")
(aggr) ) )
(de aggr ()
(let X (prod)
(while (member (car *L) '("+" "-"))
(setq X (op (if (= "+" (pop '*L)) "PLUS" "MINUS") X (prod))) )
X ) )
(de prod ()
(let X (term)
(while (member (car *L) '("*" "/"))
(setq X (op (if (= "*" (pop '*L)) "MULT" "DIV") X (term))) )
X ) )
(de term ()
(let X (pop '*L)
(cond
((num? X) X)
((= "+" X) (term))
((= "-" X) (pack "-" (term)))
((= "(" X) (prog1 (aggr) (pop '*L)))) ) ) )
(de op (Op Ex1 Ex2)
(pack Op " " (subx Ex1) " " (subx Ex2)) )
(de subx (Ex)
(if (sub? " " Ex) (pack "{" Ex "}") Ex) ) )</lang>
Output:
<pre>: (parse "1-2 - -3 * (4+5)")
-> "MINUS {MINUS 1 2} {MULT -3 {PLUS 4 5}}"
: (parse "1-2 - -3 * 4+5")
-> "PLUS {MINUS {MINUS 1 2} {MULT -3 4}} 5"
: (parse "(1+2+3)*-4/(1+2)")
-> "DIV {MULT {PLUS {PLUS 1 2} 3} -4} {PLUS 1 2}"</pre>
=={{header|Tcl}}==
| |||