Wolfram Language Paclet Repository
Community-contributed installable additions to the Wolfram Language
Wolfram`Parser`
EBNFRules  |
▪
Each record has the form : name is the rule's non-terminal name, kind is the arrow string, and body is the list of alternatives. and the body markers below are internal heads in the package's private context.
EBNFRule[name,kind,body]
EBNFRule
Wolfram`Parser`EBNFPrivate`
▪
kind is one of (syntactic), (semantic), (token construction), or (character class) — the four arrows the grammar notation distinguishes.
"::="
":=="
"::-"
":::"
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Each alternative in body is a list of elements: for a literal token, for a non-terminal reference, and for a postfix- repetition.
Lit[s]
NonTerm[name]
Rep["Many",elt]
*
▪
Rules are returned in source order.
▪
calls internally and then lowers each record to a . stops before lowering, so it is the way to inspect a parsed grammar's shape — rule count, names, and kinds — without building parsers.
Examples
(8)
Basic Examples
(4)
The raw record of a one-rule grammar:
In[1]:=
 | EBNFRules |
Out[1]=
{Wolfram`Parser`EBNFPrivate`EBNFRule[greeting,::=,{{Wolfram`Parser`EBNFPrivate`Lit[hello]},{Wolfram`Parser`EBNFPrivate`Lit[bye]}}]}
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The result is one record per rule; here a three-rule grammar yields three:
In[1]:=
Length@
[" <digit> ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 <number> ::= <digit><digit>* <expr> ::= <number> + <number>"]
 | EBNFRules |
Out[1]=
3
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The first field of each record is the rule name:
In[1]:=
| EBNFRules |
Out[1]=
{digit,number}
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The second field is the arrow kind — one grammar exercising all four the notation distinguishes:
In[1]:=
| EBNFRules |
Out[1]=
{::=,:==,::-,:::}
Scope
(2)
Properties & Relations
(2)
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""