Hello everyone,
I've been playing around with antlr and I am running into something I
don't know how to fix. Below this mail follow resp. the grammar and
tree grammar, which I've simplified to show the issue I have. Sample
input for this grammar is:
int a;
a = a+10;
String s = "hello!";
s = s + "ok";
s = a;
The problem is somewhere in the 'str_method_var' and 'int_method_var'
rules. They both have a NAME = expression semicolon . So there's the
ambiguity. I tried using a predicate in str_method_var (it now just
says {true}? as you can see) and this resolves the warning for the
grammar. Not sure if that's the right way though.
But now, the tree grammar is complaining:
[java] error(211): src/antlr/basic/test08/TestTree.g:20:2: [fatal]
rule classdef_content has non-LL(*) decision due to recursive rule
invocations reachable from alts 1,2. Resolve by left-factoring or
using syntactic predicates or using backtrack=true option.
[java] Java Result: 1
Then if I try the same trick in the tree grammar (adding {true}? in
str_method_var), it does complain:
[java] warning(203): src/antlr/basic/test08/TestTree.g:20:2: Input
such as "VARDEF" is insufficiently covered withicates at locations:
alt 2: line 40:6 at VARDEF, line 41:6 at VARDEF
[java] warning(200): src/antlr/basic/test08/TestTree.g:20:2: Decision
can match input such as "VARDEF" using multiplternatives: 1, 2
[java] As a result, alternative(s) 2 were disabled for that input
[java] error(201): src/antlr/basic/test08/TestTree.g:20:2: The
following alternatives can never be matched: 2
[java]
[java] Java Result: 1"
I am a bit lost on what to do now. I hope someone can help me out or
put me on the right track!
Thanks a lot!
Martijn
p.s. Adding {true}? predicate in the grammar unfortunately makes
antlrworks fail with a very long error dialog when trying to debug,
but I think that is this bug:
http://www.antlr.org/jira/browse/ANTLR-378.
----------------------------------------------------------------------------------
grammar Test;
options {
output=AST;
}
tokens {
VARDEF;
}
start
: classdef_content+
;
classdef_content
: int_method_var
| str_method_var
;
int_global_var
: MEMBER_TYPE_INT NAME SEMICOLON
-> ^(VARDEF
MEMBER_TYPE_INT NAME)
| MEMBER_TYPE_INT NAME '=' int_expression_calc SEMICOLON ->
^(VARDEF
MEMBER_TYPE_INT NAME int_expression_calc)
;
int_method_var
: int_global_var
| NAME '=' int_expression_calc SEMICOLON -> ^(VARDEF NAME
int_expression_calc)
;
int_expression_calc
: d=int_mult_expr_calc (('+'^ | '-'^) e=int_mult_expr_calc)*
;
int_mult_expr_calc
: int_atom ('*'^ int_atom)*
;
int_atom
: INT
| NAME
| '('! int_expression_calc ')'!
;
str_global_var
: MEMBER_TYPE_STR NAME SEMICOLON
-> ^(VARDEF
MEMBER_TYPE_STR NAME)
| MEMBER_TYPE_STR NAME '=' str_expression_calc SEMICOLON ->
^(VARDEF
MEMBER_TYPE_STR NAME str_expression_calc)
;
str_method_var
: str_global_var
| {true}? NAME '=' str_expression_calc SEMICOLON -> ^(VARDEF NAME
str_expression_calc)
;
str_expression_calc
: d=str_atom (('+'^ | '-'^) e=str_atom)*
;
str_atom
: TEXT
| NAME
;
MEMBER_TYPE_INT
: 'int'
;
MEMBER_TYPE_STR
: 'String'
;
SEMICOLON
: ';'
;
INT
: ('0'..'9')+
;
TEXT
: '"' .* '"'
;
NAME
: ('a'..'z' | 'A'..'Z' | '0'..'9' | '_' )+
;
WS
: (' '|'\t'|'\n'|'\r')+ { $channel=HIDDEN; }
;
----------------------------------------------------------------------------------
tree grammar TestTree;
options {
tokenVocab=Test;
ASTLabelType=CommonTree;
}
start
: classdef_content+
;
classdef_content
: int_method_var
| str_method_var
;
int_global_var
: ^(VARDEF MEMBER_TYPE_INT NAME)
| ^(VARDEF MEMBER_TYPE_INT NAME int_expression_calc)
;
int_method_var
: int_global_var
| ^(VARDEF NAME int_expression_calc)
;
int_expression_calc [int value]
: ^('+' a=int_expression_calc b=int_expression_calc) {
$value=a+b; }
| ^('-' a=int_expression_calc b=int_expression_calc) { $value=a-b; }
;
str_global_var
: ^(VARDEF MEMBER_TYPE_STR NAME)
| ^(VARDEF MEMBER_TYPE_STR NAME str_expression_calc)
;
str_method_var
: str_global_var
| {true}? ^(VARDEF NAME str_expression_calc)
;
str_expression_calc
: ^('+' a=str_expression_calc b=str_expression_calc) {
$value=a+b; }
| ^('-' a=str_expression_calc b=str_expression_calc) { /*$value=a-b;
*/ }
;
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