I use LPEG ( http://www.inf.puc-rio.br/~roberto/lpeg/ ) a lot for
writing grammars. I'm not familiar with the ones you mention so I
have no idea how similar they are. I too had a lot of trouble
debugging, so I ended up writing some tools that print out debugging
statements in a human readable form. The ones I've found most useful
are listing out the matched tokens in order, the tokens attempted, and
a trace of the grammar rules the parser follows. For reference, this
is a typical log of data I get (this one is for a Lua grammar):
1 1 -> block
1 2 -> chunk
1 3 -> stat
1 4 -> varlist
1 5 -> var
1 6 -> prefix
1 5 <-: prefix
1 4 <-: var
1 3 <-: varlist
1 4 -> functioncall
1 5 -> prefix
1 4 <-: prefix
1 3 <-: functioncall
2 4 -> funcname
2 3 <- funcname 3 MATCH
3 4 -> funcbody
4 5 -> parlist
4 6 -> namelist
8 5 <- namelist 9 MATCH
8 4 <- parlist 9 MATCH
10 5 -> block
10 6 -> chunk
10 7 -> stat
10 8 -> varlist
10 9 -> var
10 10 -> prefix
10 9 <- prefix 10 MATCH
11 10 -> suffix
11 11 -> call
11 12 -> args
11 13 -> tableconstructor
11 12 <-: tableconstructor
11 11 <-: args
11 10 <-: call
11 11 -> index
11 10 <-: index
11 9 <-: suffix
11 10 -> index
11 9 <-: index
10 8 <- var 11 MATCH
10 7 <- varlist 11 MATCH
10 8 -> functioncall
10 9 -> prefix
10 8 <- prefix 11 MATCH
11 9 -> suffix
11 10 -> call
11 11 -> args
11 12 -> tableconstructor
11 11 <-: tableconstructor
11 10 <-: args
11 9 <-: call
11 10 -> index
11 9 <-: index
11 8 <-: suffix
11 9 -> call
11 10 -> args
11 11 -> tableconstructor
11 10 <-: tableconstructor
11 9 <-: args
11 8 <-: call
10 7 <-: functioncall
10 6 <-: stat
10 7 -> laststat
10 6 <-: laststat
9 5 <- chunk 11 MATCH
9 4 <- block 11 MATCH
3 3 <-: funcbody
1 2 <-: stat
1 3 -> laststat
1 2 <-: laststat
0 1 <- chunk 11 MATCH
00 <- block 11 MATCH
********************************
Rule Stack:
{
idx = 9,
[1] = "block",
[2] = "chunk",
[3] = "stat",
[4] = "funcbody",
[5] = "block",
[6] = "chunk",
[7] = "stat",
[8] = "functioncall",
[9] = "prefix",
}
********************************
Attempted Tokens List:
{
rules = {
[1] = "args",
[2] = "tableconstructor",
[3] = "args",
[4] = "call",
[5] = "index",
[6] = "index",
[7] = "varlist",
[8] = "stat",
},
tokens = {
[1] = "LEFT_PAREN",
[2] = "LEFT_BRACE",
[3] = "STRING",
[4] = "COLON",
[5] = "LEFT_BRACKET",
[6] = "DOT",
[7] = "COMMA",
[8] = "EQUALS",
},
}
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