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|
grammar t018llstar;
options {
language = Python3;
}
@header {
from io import StringIO
}
@init {
self.output = StringIO()
}
program
: declaration+
;
/** In this rule, the functionHeader left prefix on the last two
* alternatives is not LL(k) for a fixed k. However, it is
* LL(*). The LL(*) algorithm simply scans ahead until it sees
* either the ';' or the '{' of the block and then it picks
* the appropriate alternative. Lookhead can be arbitrarily
* long in theory, but is <=10 in most cases. Works great.
* Use ANTLRWorks to see the lookahead use (step by Location)
* and look for blue tokens in the input window pane. :)
*/
declaration
: variable
| functionHeader ';'
{self.output.write($functionHeader.name+" is a declaration\n")}
| functionHeader block
{self.output.write($functionHeader.name+" is a definition\n")}
;
variable
: type declarator ';'
;
declarator
: ID
;
functionHeader returns [name]
: type ID '(' ( formalParameter ( ',' formalParameter )* )? ')'
{$name = $ID.text}
;
formalParameter
: type declarator
;
type
: 'int'
| 'char'
| 'void'
| ID
;
block
: '{'
variable*
stat*
'}'
;
stat: forStat
| expr ';'
| block
| assignStat ';'
| ';'
;
forStat
: 'for' '(' assignStat ';' expr ';' assignStat ')' block
;
assignStat
: ID '=' expr
;
expr: condExpr
;
condExpr
: aexpr ( ('==' | '<') aexpr )?
;
aexpr
: atom ( '+' atom )*
;
atom
: ID
| INT
| '(' expr ')'
;
ID : ('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')*
;
INT : ('0'..'9')+
;
WS : ( ' '
| '\t'
| '\r'
| '\n'
)+
{$channel=HIDDEN}
;
|
