I can take a guess at what is happening. Since, as Ron points out, the
example is a bit large, I did not check this in detail, so feel free to
follow up if this does not help.
G1 thinks that <name> is a lexeme. L0 disagrees.
In more detail, G1 finds that <name> is on the RHS of one of its rules,
and not on a LHS. So G1 concludes that <name> is a lexeme. L0 looks
for <name> on the *LHS* of one of its rules. It does find it on the LHS
of an L0 rule, as required. But it also finds this:
names ~ name+
Here <name> appears on the RHS of an L0 rule, which tells Marpa that is
it not a lexeme, after all. One solution (if my guess is right) is to
rewrite so that <name> is not on the RHS of any L0 rules.
What Marpa is doing is figuring out the boundary between G1 and L0 for
you, based on how you used the symbols. If you use them inconsistently,
it can't do this and complains. One of its messages of complaint is the
one you got.
In the doc
https://metacpan.org/pod/distribution/Marpa-R2/pod/Scanless.pod there's
an even more detailed discussion of this.
Again, feel free to follow up if this doesn't help.
-- jeffrey
On 05/01/2014 02:43 PM, Michael Roberts wrote:
Apologies in advance for not cutting my grammar down to isolate the
error, but I'm having a problem understanding an error when I try to
modify the following grammar:
:default ::= action => [name,values]
lexeme default = latm => 1
:start ::= line
line ::= name_group sep parmgroup sep sigil sep comment
name_group ::= tag | tag whitespace names
sep ::= whitespace
sep ::=
whitespace ~ [\s]+
tag ::= tag_name
tag_name ~ <plain tag> | <annotation tag>
<plain tag> ~ [\w]+
<annotation tag> ~ '[' <plain tag> ']'
names ~ name+
name ~ [\w]+
parmgroup ::= paren_group | bracket_group | string
parmgroup ::=
paren_group ::= '(' parm_list ')'
bracket_group ::= '[' parm_list ']'
parm_list ::= parm* separator => <comma>
parm ::= words | words '=' string
words ~ name+
sigil ::= ':' | '::' | ':*' | '{' | '[' | '<' | '('
| sigil template_spec
sigil ::=
template_spec ::= '?' <up_to_comment>
<up_to_comment> ~ [^#]
<comma> ~ [,]
string ::= sqstr || dqstr # Strings stolen from
MarpaX::Demo::JSONParser
sqstr ~ sq <sq contents> sq
dqstr ~ dq <dq contents> dq
sq ~ [']
dq ~ ["]
<sq contents> ~ <sq char>*
<dq contents> ~ <dq char>*
<sq char> ~ [^'\\] | '\' <any char>
<dq char> ~ [^"\\] | '\' <any char>
<any char> ~ [\d\D]
comment ::= hash_comment # No comment, or comment
consisting of a hash followed by everything else in the string.
comment ::=
hash_comment ~ '#' anything
anything ~ <any char>*
The above grammar works fine on my test string, but when I make
"names" a ::=-rule instead of a ~-rule, like this:
names ::= name
I get the following error:
A lexeme in G1 is not a lexeme in any of the lexers: name
OK, so 'name' is clearly still a lexeme in a lexer if I understand the
terminology correctly. What am I missing? I get a similar error if I
try to use "separator => whitespace" - except now it can't find
whitespace. Clearly I am entirely barking up the wrong tree here.
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