I'm trying to learn a bit ANTLR4 and define a grammar for some 4GL language.
This is what I've got:
compileUnit
:
typedeclaration EOF
;
typedeclaration
:
ID LPAREN DATATYPE INT RPAREN
;
DATATYPE
:
DATATYPE_ALPHANUMERIC
| DATATYPE_NUMERIC
;
DATATYPE_ALPHANUMERIC
:
'A'
;
DATATYPE_NUMERIC
:
'N'
;
fragment
DIGIT
:
[0-9]
;
fragment
LETTER
:
[a-zA-Z]
;
INT
:
DIGIT+
;
ID
:
LETTER
(
LETTER
| DIGIT
)*
;
LPAREN
:
'('
;
RPAREN
:
')'
;
WS
:
[ \t\f]+ -> skip
;
What I want to be able to parse:
TEST (A10)
what I get:
typedeclaration:1:6: mismatched input 'A10' expecting DATATYPE
I am however able to write:
TEST (A 10)
Why do I need to put a whitespace in here? The LPAREN DATATYPE in itself is working, so there is no need for a space inbetween. Also the INT RPAREN is working.
Why is a space needed between DATATYPE and INT? I'm a bit confused on that one.
I guess that it's matching ID because it's the "longest" match, but there must be some way to force to be lazier here, right?
You should ignore 'A' and 'N' chats at first position of ID. As #CoronA noticed ANTLR matches token as long as possible (length of ID 'A10' more than length of DATATYPE_ALPHANUMERIC 'A'). Also read this: Priority rules. Try to use the following grammar:
grammar expr;
compileUnit
: typedeclaration EOF
;
typedeclaration
: ID LPAREN datatype INT RPAREN
;
datatype
: DATATYPE_ALPHANUMERIC
| DATATYPE_NUMERIC
;
DATATYPE_ALPHANUMERIC
: 'A'
;
DATATYPE_NUMERIC
: 'N'
;
INT
: DIGIT+
;
ID
: [b-mo-zB-MO-Z] (LETTER | DIGIT)*
;
LPAREN
: '('
;
RPAREN
: ')'
;
WS
: [ \t\f]+ -> skip
;
fragment
DIGIT
: [0-9]
;
fragment
LETTER
: [a-zA-Z]
;
Also you can use the following grammar without id restriction. Data types will be recognized earlier than letters. it's not clear too:
grammar expr;
compileUnit
: typedeclaration EOF
;
typedeclaration
: id LPAREN datatype DIGIT+ RPAREN
;
id
: (datatype | LETTER) (datatype | LETTER | DIGIT)*
;
datatype
: DATATYPE_ALPHANUMERIC
| DATATYPE_NUMERIC
;
DATATYPE_ALPHANUMERIC: 'A';
DATATYPE_NUMERIC: 'N';
// List with another Data types.
LETTER: [a-zA-Z];
LPAREN
: '('
;
RPAREN
: ')'
;
WS
: [ \t\f]+ -> skip
;
DIGIT
: [0-9]
;
Related
I have tried to write a grammar to recognize expressions like:
(A + MAX(B) ) / ( C - AVERAGE(A) )
IF( A > AVERAGE(A), 0, 1 )
X / (MAX(X)
Unfortunately antlr3 fails with these errors:
error(210): The following sets of rules are mutually left-recursive [unaryExpression, additiveExpression, primaryExpression, formula, multiplicativeExpression]
error(211): DerivedKeywords.g:110:13: [fatal] rule booleanTerm 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.
error(206): DerivedKeywords.g:110:13: Alternative 1: after matching input such as decision cannot predict what comes next due to recursion overflow to additiveExpression from formula
I have spent some hours trying to fix these, it would be great if anyone could at least help me fix the first problem. Thanks
Code:
grammar DerivedKeywords;
options {
output=AST;
//backtrack=true;
}
WS : ( ' ' | '\t' | '\n' | '\r' )
{ skip(); }
;
//for numbers
DIGIT
: '0'..'9'
;
//for both integer and real number
NUMBER
: (DIGIT)+ ( '.' (DIGIT)+ )?( ('E'|'e')('+'|'-')?(DIGIT)+ )?
;
// Boolean operatos
AND : 'AND';
OR : 'OR';
NOT : 'NOT';
EQ : '=';
NEQ : '!=';
GT : '>';
LT : '<';
GTE : '>=';
LTE : '<=';
COMMA : ',';
// Token for Functions
IF : 'IF';
MAX : 'MAX';
MIN : 'MIN';
AVERAGE : 'AVERAGE';
VARIABLE : 'A'..'Z' ('A'..'Z' | '0'..'9')*
;
// OPERATORS
LPAREN : '(' ;
RPAREN : ')' ;
DIV : '/' ;
PLUS : '+' ;
MINUS : '-' ;
STAR : '*' ;
expression : formula;
formula
: functionExpression
| additiveExpression
| LPAREN! a=formula RPAREN! // First Problem
;
additiveExpression
: a=multiplicativeExpression ( (MINUS^ | PLUS^ ) b=multiplicativeExpression )*
;
multiplicativeExpression
: a=unaryExpression ( (STAR^ | DIV^ ) b=unaryExpression )*
;
unaryExpression
: MINUS^ u=unaryExpression
| primaryExpression
;
functionExpression
: f=functionOperator LPAREN e=formula RPAREN
| IF LPAREN b=booleanExpression COMMA p=formula COMMA s=formula RPAREN
;
functionOperator :
MAX | MIN | AVERAGE;
primaryExpression
: NUMBER
// Used for scientific numbers
| DIGIT
| VARIABLE
| formula
;
// Boolean stuff
booleanExpression
: orExpression;
orExpression : a=andExpression (OR^ b=andExpression )*
;
andExpression
: a=notExpression (AND^ b=notExpression )*
;
notExpression
: NOT^ t=booleanTerm
| booleanTerm
;
booleanOperator :
GT | LT | EQ | GTE | LTE | NEQ;
booleanTerm : a=formula op=booleanOperator b=formula
| LPAREN! booleanTerm RPAREN! // Second problem
;
error(210): The following sets of rules are mutually left-recursive [unaryExpression, additiveExpression, primaryExpression, formula, multiplicativeExpression]
- this means that if the parser enters unaryExpression rule, it has the possibility to match additiveExpression, primaryExpression, formula, multiplicativeExpression and unaryExpression again without ever consuming a single token from input - so it cannot decide whether to use those rules or not, because even if it uses the rules, the input will be the same.
You're probably trying to allow subexpressions in expressions by this sequence of rules - you need to make sure that path will consume the left parenthesis of the subexpression. Probably the formula alternative in primaryExpression should be changed to LPAREN formula RPAREN, and the rest of grammar be adjusted accordingly.
I have an AlgebraRelacional.g4 file with this. I need to read a file with a syntax like a CSV file, put the content in some memory tables and then resolve relational algebra operations with that. Can you tell me if I am doing it right?
Example data file to read:
cod_buy(char);name_suc(char);Import(int);date_buy(date)
“P-11”;”DC Med”;900;01/03/14
“P-14”;”Center”;1500;02/05/14
Current ANTLR grammar:
grammar AlgebraRelacional;
SEL : '\u03C3'
;
PRO : '\u220F'
;
UNI : '\u222A'
;
DIF : '\u002D'
;
PROC : '\u0058'
;
INT : '\u2229'
;
AND : 'AND'
;
OR : 'OR'
;
NOT : 'NOT'
;
EQ : '='
;
DIFERENTE : '!='
;
MAYOR : '>'
;
MENOR : '<'
;
SUMA : '+'
;
MULTI : '*'
;
IPAREN : '('
;
DPAREN : ')'
;
COMA : ','
;
PCOMA : ';'
;
Comillas: '"'
;
file : hdr row+ ;
hdr : row ;
row : field (',' field)* '\r'? '\n' ;
field : TEXT | STRING | ;
TEXT : ~[,\n\r"]+ ;
STRING : '"' ('""'|~'"')* '"' ;
I suggest you that read this document (http://is.muni.cz/th/208197/fi_b/bc_thesis.pdf), It contains usefull information about how to write a parser for relational algebra. That is not ANTLR, but you only has to translate the grammar in BNF to EBNF.
I’m currently trying to build a parser for the language Oberon using Antlr and Ecplise.
This is what I have got so far:
grammar oberon;
options
{
language = Java;
//backtrack = true;
output = AST;
}
#parser::header {package dhbw.Oberon;}
#lexer::header {package dhbw.Oberon; }
T_ARRAY : 'ARRAY' ;
T_BEGIN : 'BEGIN';
T_CASE : 'CASE' ;
T_CONST : 'CONST' ;
T_DO : 'DO' ;
T_ELSE : 'ELSE' ;
T_ELSIF : 'ELSIF' ;
T_END : 'END' ;
T_EXIT : 'EXIT' ;
T_IF : 'IF' ;
T_IMPORT : 'IMPORT' ;
T_LOOP : 'LOOP' ;
T_MODULE : 'MODULE' ;
T_NIL : 'NIL' ;
T_OF : 'OF' ;
T_POINTER : 'POINTER' ;
T_PROCEDURE : 'PROCEDURE' ;
T_RECORD : 'RECORD' ;
T_REPEAT : 'REPEAT' ;
T_RETURN : 'RETURN';
T_THEN : 'THEN' ;
T_TO : 'TO' ;
T_TYPE : 'TYPE' ;
T_UNTIL : 'UNTIL' ;
T_VAR : 'VAR' ;
T_WHILE : 'WHILE' ;
T_WITH : 'WITH' ;
module : T_MODULE ID SEMI importlist? declarationsequence?
(T_BEGIN statementsequence)? T_END ID PERIOD ;
importlist : T_IMPORT importitem (COMMA importitem)* SEMI ;
importitem : ID (ASSIGN ID)? ;
declarationsequence :
( T_CONST (constantdeclaration SEMI)*
| T_TYPE (typedeclaration SEMI)*
| T_VAR (variabledeclaration SEMI)*)
(proceduredeclaration SEMI | forwarddeclaration SEMI)*
;
constantdeclaration: identifierdef EQUAL expression ;
identifierdef: ID MULT? ;
expression: simpleexpression (relation simpleexpression)? ;
simpleexpression : (PLUS|MINUS)? term (addoperator term)* ;
term: factor (muloperator factor)* ;
factor: number
| stringliteral
| T_NIL
| set
| designator '(' explist? ')'
;
number: INT | HEX ; // TODO add real
stringliteral : '"' ( ~('\\'|'"') )* '"' ;
set: '{' elementlist? '}' ;
elementlist: element (COMMA element)* ;
element: expression (RANGESEP expression)? ;
designator: qualidentifier
('.' ID
| '[' explist ']'
| '(' qualidentifier ')'
| UPCHAR )+
;
explist: expression (COMMA expression)* ;
actualparameters: '(' explist? ')' ;
muloperator: MULT | DIV | MOD | ET ;
addoperator: PLUS | MINUS | OR ;
relation: EQUAL ; // TODO
typedeclaration: ID EQUAL type ;
type: qualidentifier
| arraytype
| recordtype
| pointertype
| proceduretype
;
qualidentifier: (ID '.')* ID ;
arraytype: T_ARRAY expression (',' expression) T_OF type;
recordtype: T_RECORD ('(' qualidentifier ')')? fieldlistsequence T_END ;
fieldlistsequence: fieldlist (SEMI fieldlist) ;
fieldlist: (identifierlist COLON type)? ;
identifierlist: identifierdef (COMMA identifierdef)* ;
pointertype: T_POINTER T_TO type ;
proceduretype: T_PROCEDURE formalparameters? ;
variabledeclaration: identifierlist COLON type ;
proceduredeclaration: procedureheading SEMI procedurebody ID ;
procedureheading: T_PROCEDURE MULT? identifierdef formalparameters? ;
formalparameters: '(' params? ')' (COLON qualidentifier)? ;
params: fpsection (SEMI fpsection)* ;
fpsection: T_VAR? idlist COLON formaltype ;
idlist: ID (COMMA ID)* ;
formaltype: (T_ARRAY T_OF)* (qualidentifier | proceduretype);
procedurebody: declarationsequence (T_BEGIN statementsequence)? T_END ;
forwarddeclaration: T_PROCEDURE UPCHAR? ID MULT? formalparameters? ;
statementsequence: statement (SEMI statement)* ;
statement : assignment
| procedurecall
| ifstatement
| casestatement
| whilestatement
| repeatstatement
| loopstatement
| withstatement
| T_EXIT
| T_RETURN expression?
;
assignment: designator ASSIGN expression ;
procedurecall: designator actualparameters? ;
ifstatement: T_IF expression T_THEN statementsequence
(T_ELSIF expression T_THEN statementsequence)*
(T_ELSE statementsequence)? T_END ;
casestatement: T_CASE expression T_OF caseitem ('|' caseitem)*
(T_ELSE statementsequence)? T_END ;
caseitem: caselabellist COLON statementsequence ;
caselabellist: caselabels (COMMA caselabels)* ;
caselabels: expression (RANGESEP expression)? ;
whilestatement: T_WHILE expression T_DO statementsequence T_END ;
repeatstatement: T_REPEAT statementsequence T_UNTIL expression ;
loopstatement: T_LOOP statementsequence T_END ;
withstatement: T_WITH qualidentifier COLON qualidentifier T_DO statementsequence T_END ;
ID : ('a'..'z'|'A'..'Z')('a'..'z'|'A'..'Z'|'_'|'0'..'9')* ;
fragment DIGIT : '0'..'9' ;
INT : ('-')?DIGIT+ ;
fragment HEXDIGIT : '0'..'9'|'A'..'F' ;
HEX : HEXDIGIT+ 'H' ;
ASSIGN : ':=' ;
COLON : ':' ;
COMMA : ',' ;
DIV : '/' ;
EQUAL : '=' ;
ET : '&' ;
MINUS : '-' ;
MOD : '%' ;
MULT : '*' ;
OR : '|' ;
PERIOD : '.' ;
PLUS : '+' ;
RANGESEP : '..' ;
SEMI : ';' ;
UPCHAR : '^' ;
WS : ( ' ' | '\t' | '\r' | '\n'){skip();};
My problem is when I check the grammar I get the following error and just can’t find an appropriate way to fix this:
rule statement 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.
|---> statement : assignment
Also I have the problem with declarationsequence and simpleexpression.
When I use options { … backtrack = true; … } it at least compiles, but obviously doesn’t work right anymore when I run a test-file, but I can’t find a way to resolve the left-recursion on my own (or maybe I’m just too blind at the moment because I’ve looked at this for far too long now). Any ideas how I could change the lines where the errors occurs to make it work?
EDIT
I could fix one of the three mistakes. statement works now. The problem was that assignment and procedurecall both started with designator.
statement : procedureassignmentcall
| ifstatement
| casestatement
| whilestatement
| repeatstatement
| loopstatement
| withstatement
| T_EXIT
| T_RETURN expression?
;
procedureassignmentcall : (designator ASSIGN)=> assignment | procedurecall;
assignment: designator ASSIGN expression ;
procedurecall: designator actualparameters? ;
I'm trying to make parser using Antlr4 for the sql select statement, in which contains the following part
expr: '1' | expr('*'|'/'|'+'|'-'|'||') expr; // As the re-factored form of expression: compound expression;
WS :[ \t\r\n]+ -> skip ;
I suppose this rule will allow the following sets of result:
1
1+1
1+1-1
....
But in the graph it shows that it cannot be parsed
Does anyone get the idea why it cannot be parsed like what i expected?
This slightly adjusted grammar works for me. Tested on input 1+1-1||1*1-1/1. Tested in ANTLRWorks2.1
grammar myGrammar;
top : expr EOF ;
expr : '1'
| expr '+' expr
| expr '*' expr
| expr '/' expr
| expr '+' expr
| expr '-' expr
| expr '||' expr
;
WS :[ \t\r\n]+ -> skip ;
One : '1' ;
Times : '*' ;
Div : '/' ;
Plus : '+' ;
Minus : '-' ;
Or : '||' ;
EDIT
I was able to get this to work, too, when matching the rule top:
grammar newEmptyCombinedGrammar;
top : expr EOF ;
expr: one
| expr op=(Times|Div|Plus|Minus|Or) expr
;
one : One ;
One : '1' ;
Times : '*' ;
Div : '/' ;
Plus : '+' ;
Minus : '-' ;
Or : '||' ;
WS :[ \t\r\n]+ -> skip ;
I'm trying to built C-- compiler using ANTLR 3.4.
Full set of the grammar listed here,
program : (vardeclaration | fundeclaration)* ;
vardeclaration : INT ID (OPENSQ NUM CLOSESQ)? SEMICOL ;
fundeclaration : typespecifier ID OPENP params CLOSEP compoundstmt ;
typespecifier : INT | VOID ;
params : VOID | paramlist ;
paramlist : param (COMMA param)* ;
param : INT ID (OPENSQ CLOSESQ)? ;
compoundstmt : OPENCUR vardeclaration* statement* CLOSECUR ;
statementlist : statement* ;
statement : expressionstmt | compoundstmt | selectionstmt | iterationstmt | returnstmt;
expressionstmt : (expression)? SEMICOL;
selectionstmt : IF OPENP expression CLOSEP statement (options {greedy=true;}: ELSE statement)?;
iterationstmt : WHILE OPENP expression CLOSEP statement;
returnstmt : RETURN (expression)? SEMICOL;
expression : (var EQUAL expression) | sampleexpression;
var : ID ( OPENSQ expression CLOSESQ )? ;
sampleexpression: addexpr ( ( LOREQ | LESS | GRTR | GOREQ | EQUAL | NTEQL) addexpr)?;
addexpr : mulexpr ( ( PLUS | MINUS ) mulexpr)*;
mulexpr : factor ( ( MULTI | DIV ) factor )*;
factor : ( OPENP expression CLOSEP ) | var | call | NUM;
call : ID OPENP arglist? CLOSEP;
arglist : expression ( COMMA expression)*;
Used lexer rules as following,
ELSE : 'else' ;
IF : 'if' ;
INT : 'int' ;
RETURN : 'return' ;
VOID : 'void' ;
WHILE : 'while' ;
PLUS : '+' ;
MINUS : '-' ;
MULTI : '*' ;
DIV : '/' ;
LESS : '<' ;
LOREQ : '<=' ;
GRTR : '>' ;
GOREQ : '>=' ;
EQUAL : '==' ;
NTEQL : '!=' ;
ASSIGN : '=' ;
SEMICOL : ';' ;
COMMA : ',' ;
OPENP : '(' ;
CLOSEP : ')' ;
OPENSQ : '[' ;
CLOSESQ : ']' ;
OPENCUR : '{' ;
CLOSECUR: '}' ;
SCOMMENT: '/*' ;
ECOMMENT: '*/' ;
ID : ('a'..'z' | 'A'..'Z')+/*(' ')*/ ;
NUM : ('0'..'9')+ ;
WS : (' ' | '\t' | '\n' | '\r')+ {$channel = HIDDEN;};
COMMENT: '/*' .* '*/' {$channel = HIDDEN;};
But I try to save this it give me the error,
error(211): /CMinusMinus/src/CMinusMinus/CMinusMinus.g:33:13: [fatal] rule expression 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.
|---> expression : (var EQUAL expression) | sampleexpression;
1 error
How can I resolve this problem?
As already mentioned: your grammar rule expression is ambiguous: both alternatives in that rule start, or can be, a var.
You need to "help" your parser a bit. If the parse can see a var followed by an EQUAL, it should choose alternative 1, else alternative 2. This can be done by using a syntactic predicate (the (var EQUAL)=> part in the rule below).
expression
: (var EQUAL)=> var EQUAL expression
| sampleexpression
;
More about predicates in this Q&A: What is a 'semantic predicate' in ANTLR?
The problem is this:
expression : (var EQUAL expression) | sampleexpression;
where you either start with var or sampleexpression. But sampleexpression can be reduced to var as well by doing sampleexpression->addExpr->MultExpr->Factor->var
So there is no way to find a k-length predicate for the compiler.
You can as suggested by the error message set backtrack=true to see whether this solves your problem, but it might lead not to the AST - parsetrees you would expect and might also be slow on special input conditions.
You could also try to refactor your grammar to avoid such recursions.