这是我第一次使用CUP解析器而且我一直收到以下错误： “警告： * 生产”......“从未使用过。 我无法弄清楚出了什么问题，请帮忙。 请参阅下面的代码和错误日志，谢谢。
package adtl;
import java_cup.runtime.*;
import java.util.*;
import adtl.Lexer.*;
import adtl.ast.*;
parser code {:
public void syntax_error(java_cup.runtime.Symbol current) {
Token t = (Token) current;
throw new SyntaxError("Syntax error in line " + t.line + " '" + t.toText() + "'");
}
:};
/* Terminals (tokens returned by the scanner). */
terminal SET, LOCK, LCBR, RCBR, COLON , SEMICOLON, AT , REV , LP, RP, DOT, COMMA, RETURN, ELSE,...
/* Non-terminals */
non terminal ADT ADT;
non terminal Element Element;
non terminal ElementList ElementList;
non terminal FieldDef FieldDef;
non terminal Type Type;
non terminal MethodDef MethodDef;
non terminal Args Arg;
non terminal Args Args;
non terminal Stmt Stmt ;
non terminal StmtList StmtList ;
non terminal Assign Assign ;
non terminal StmtList SingleOrBlockStmt ;
non terminal Expr Expr ;
non terminal AssignedArgs AssignedArg ;
non terminal PathExpr PathExpr ;
non terminal PathElement PathElement ;
/* Precedences */
precedence left PLUS, MINUS, TIMES, DIVIDE, LOR, LAND, ELSE;
precedence nonassoc CHOOSE, LOR, LAND, NOT, LT, LTE, GT, GTE, EQ...
/* The grammar */
ADT ::= ID:name LCBR ElementList:l RCBR
{: RESULT = new ADT(name, l); :};
ElementList ::= ElementList:eList Element:e
{:RESULT= eList.append(e) ;:}
|Element:e
{:RESULT = new ElementList(e);:}
|
{:RESULT = new ElementList();:};
ELEMENT ::= FieldDef:def | MethodDef: def
{:RESULT = def;:};
FieldDef ::= ID:name COLON Type:type SEMICOLON
{:RESULT = new FieldDef(name, type);:};
Type ::= ID:name
{:RESULT = new Type(name):}
| SET
{:RESULT = new Type("set");:};
MethodDef ::= ID:name LP Args:args RP LCBR StmtList:stmts RCBR
{:RESULT = new MethodDef(name, args, stmts);:}
|ID:name LP RP LCBR StmtList:stmts RCBR
{:RESULT = new MethodDef(name, new Args(), stmts);:};
StmtList ::= Stmt:stmt StmtList:sList
{:RESULT= sList.append(stmt) ;:}
|Stmt:stmt
{:RESULT = stmt;:}
|
{:RESULT = new StmtList();:};
Args ::= ID:name COLON Type:type COMMA Args:args
{:RESULT = args.append(name , type);:}
| Arg:arg
{:RESULT = arg ;:};
Arg ::= ID:name COLON Type:type
{:RESULT = new Args(name, type);:};
Stmt ::= RETURN Expr:exp SEMICOLON
{:RESULT = new Return(exp);:}
| Assign:ass SEMICOLON
{:RESULT = ass;:}
| IF LP Expr:cond RP SingleOrBlockStmt:sobstmt
{:RESULT = new Condition(cond, sobstmt);:}
| IF LP Expr:cond RP SingleOrBlockStmt:sobstmt1 ELSE SingleOrBlockStmt:sobstmt2
{:RESULT = new Condition(cond, sobstmt1, sobstmt2 ;:}
| ASSERT Expr:exp SEMICOLON
{:RESULT = new Assert(exp, "" );:}
| ASSERT Expr:exp COLON QUOTE:str SEMICOLON
{:RESULT = new Assert(exp, str );:}
| LOCK PathExpr:pexp SEMICOLON
{:RESULT = new Lock(pexp);:};
Assign ::= PathExpr:pexp ASSIGN Expr:exp
{:RESULT = new Assign(pexpr, exp);:};
Assign ::= PathExpr:pexp ASSIGN_PLUS Expr:exp
{:RESULT = new Assign(pexp, new BinaryExpr(Ops.PLUS, pexp, exp));:};
Assign ::= PathExpr:pexp ASSIGN_MINUS Expr:exp
{:RESULT = new Assign(pexpr, new BinaryExpr(Ops.MINUS,pexp, exp);:};
SingleOrBlockStmt ::= Stmt:stmt
{:RESULT = stmt ;:}
| LCBR Stmt:stmt StmtList:list RCBR
{:RESULT = (new StmtList(list)).append(stmt);:};
Expr ::= CHOOSE Expr:exp
{:RESULT = new Choose(exp);:}
| INT:num
{:RESULT = new INT(num);:}
| BAR Expr:exp BAR
{:RESULT = new SizeExp(exp);:}
| NEW Type:type LP AssignedArg:assArgs COMMA RP
{:RESULT = new NewExpr(type, assArgs);:}
| MINUS Expr:exp
{:RESULT = new BinaryExp(Ops.MINUS, new INT(0), exp);:}
|Expr:exp1 PLUS Expr:exp2
{:RESULT = new BinaryExpr(Ops.PLUS ,exp1, exp2);:}
|Expr:exp1 TIMES Expr:exp2
{:RESULT = new BinaryExpr(Ops.TIMES ,exp1, exp2);:}
|Expr:exp1 MINUS Expr:exp2
{:RESULT = new BinaryExpr(Ops.MINUS ,exp1, exp2);:}
|Expr:exp1 DIVIDE Expr:exp2
{:RESULT = new BinaryExpr(Ops.DIVIDE ,exp1, exp2);:}
|Expr:exp1 LT Expr:exp2
{:RESULT = new BinaryExpr(Ops.LT ,exp1, exp2);:}
|Expr:exp1 LTE Expr:exp2
{:RESULT = new BinaryExpr(Ops.LTE ,exp1, exp2);:}
|Expr:exp1 GT Expr:exp2
{:RESULT = new BinaryExpr(Ops.GT ,exp1, exp2);:}
|Expr:exp1 GTE Expr:exp2
{:RESULT = new BinaryExpr(Ops.GTE ,exp1, exp2);:}
|Expr:exp1 EQ Expr:exp2
{:RESULT = new BinaryExpr(Ops.EQ ,exp1, exp2);:}
|Expr:exp1 NEQ Expr:exp2
{:RESULT = new BinaryExpr(Ops.NEQ ,exp1, exp2);:}
| NOT Expr:exp
{:RESULT = new NotExpr(exp);:}
|Expr:exp1 LAND Expr:exp2
{:RESULT = new BinaryExpr(Ops.LAND ,exp1, exp2);:}
|Expr:exp1 LOR Expr:exp2
{:RESULT = new BinaryExpr(Ops.LOR ,exp1, exp2);:}
|Expr:exp1 IN Expr:exp2
{:RESULT = new BinaryExpr(Ops.IN ,exp1, exp2);:}
| PathExpr:pexp
{:RESULT = new PathExpr(pexp);:}
| LP Expr:exp RP
{:RESULT = exp;:};
AssignedArg ::= ID:name ASSIGN Expr:exp
{: RESULT = new AssignedArgs(name, exp);:};
PathExpr ::= PathElement:pele DOT PathExpr:pexpr
{:RESULT = pexpr.append(pele);:}
| PathElement:pel
{:RESULT = new PathExpr(pel);:};
PathElement ::= ID:name AT
{: RESULT = new PathElement(name, false, true);:}
| ID:name
{: RESULT = new PathElement(name, false , false);:}
| REV LP ID:name RP AT
{: RESULT = new PathElement(name, true , true);:}
| REV LP ID:name RP
{: RESULT = new PathElement(name, true , false);:};
错误日志：
\adtl\ADTL.cup
Warning : LHS non terminal "ELEMENT" has not been declared
Warning : Terminal "UMINUS" was declared but never used
Warning : *** Production "PathElement ::= REV LP ID RP " never reduced
Warning : *** Production "PathElement ::= REV LP ID RP AT " never reduced
Warning : *** Production "PathElement ::= ID " never reduced
Warning : *** Production "PathElement ::= ID AT " never reduced
Warning : *** Production "PathExpr ::= PathElement " never reduced
Warning : *** Production "PathExpr ::= PathElement DOT PathExpr " never reduced
Warning : *** Production "Type ::= SET " never reduced
Warning : *** Production "Type ::= ID " never reduced
Warning : *** Production "FieldDef ::= ID COLON Type SEMICOLON " never reduced
------- CUP v0.11a beta 20060608 Parser Generation Summary -------
0 errors and 53 warnings
42 terminals, 16 non-terminals, and 56 productions declared,
producing 9 unique parse states.
1 terminal declared but not used.
0 non-terminal declared but not used.
0 productions never reduced.
0 conflicts detected (0 expected).
Code written to "parser.java", and "sym.java".
---------------------------------------------------- (v0.11a beta 20060608)
答案 0 :(得分：1)
我很确定如果您在制作中正确拼写Element而不是拼写ELEMENT，那么大多数（如果不是全部）这些错误都会消失。