Wolfram Language Paclet Repository
Community-contributed installable additions to the Wolfram Language
Wolfram`Parser`
ParseRecursive  |
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The reference stores the symbol name, not the parser it currently names: is .
ParseRecursive[s]
ParserCombinator["Recursive",Hold[s],]
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The lazy lookup lets a grammar be self-referential - a symbol whose definition mentions itself - or mutually recursive - symbols that mention each other - without pre-declaring every node.
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symbol must be bound to a by the time runs; it is resolved at parse time, not at construction.
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A recursive grammar runs on the interpretive engine, and the recursive-descent nesting is bounded by a depth guard, so deeply nested input returns a rather than overflowing the stack.
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Examples
(9)
Basic Examples
(3)
The reference holds a symbol and looks it up at parse time, so it can be built before the grammar is defined:
In[1]:=
 | ParseRecursive |
Out[1]=
ParserCombinator
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A self-referential grammar - a value is a number, or a bracketed comma-separated list of values - refers back to itself through :
ParseRecursive
In[1]:=
value=
[DigitCharacter]..,FromDigits@*StringJoin,
"["],
[value],
[","],
["]";
[value,"[1,[2,3],4]"]
 | ParseChoice |
 | ParseAction |
 | ParseCharacter |
| ParseBetween |
| ParseLiteral |
| ParseSepBy |
| ParseRecursive |
| ParseLiteral |
| ParseLiteral |
| Parse |
Out[1]=
{1,{2,3},4}
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The base case - a bare number - needs no recursion:
In[1]:=
| Parse |
Out[1]=
42
Scope
(4)
Properties & Relations
(1)
Possible Issues
(1)
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""