Hi,
the language for which I am trying to build the grammar has 2 flavors
of if-then-else constructs
- a single line : if <condition> then <statement> [else <statement>]
- a multi line : if <condition> then <statements> [else <statements>] end if
I have defined the following (partial) :
codeBlock
: (compoundStatement)*
;
compoundStatement
: (
ifStatement
| singleStatement
) (';' | EOL)
;
singleStatement
: localVariableDeclaration
| funCall
| 'return' expression
;
ifStatement
: singleLineIf
| multiLineIf
;
singleLineIf
: 'if' expression 'then' singleStatement EOL
;
multiLineIf
: 'if' expression 'then' codeBlock 'end if'
;
I understand why the naive ifStatement fails with the following "
[fatal] rule ifStatement 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."
I would like to avoid general backtracking, so after searching for a
while and reading the article
http://www.antlr.org/wiki/display/ANTLR3/How+to+remove+global+backtracking+from+your+grammar
I have tried first
ifStatement
: 'if' expression 'then' (singleStatement EOL)=> singleLineIf
| multiLineIf
;
or
ifStatement
: 'if' expression 'then' (singleStatement EOL | codeBlock 'end
if')
;
But they fail both with the same fatality.
How this case should be processed ?
--
Sébastien Kirche
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