Bison/Flex 中的 If/Then 语句和 switch 语句

Question

编辑：if 语句正在工作，在 values.cc 中的evaluateRelational() 中用“==”拼写相等和用“！=”拼写不等之后。 谢谢@rici！ 现在为 switch 语句...

我一直在尝试在 Bison/Flex 编译器中实现 if-then 语句和 switch 语句。 我很困惑为什么 values.cc 中的 evaluteIfThen() 不起作用，以及如何开始接近使 switch 语句起作用。 对于 if-then 语句，无论条件如何满足，它目前都只识别第一个结果（“if”块）。 如在下面的测试输入中，无论参数 a 是什么，它都返回 10。

请帮忙！ 非常感谢你！

这是使用该语言编写的 if-then 语句的测试输入：

-- Function with parameters

function main a: integer returns integer;
   c: integer is 5;
begin
   if a = 1 then
    c + 5;
   else 
    c + 10;
   endif;
end;

使用 switch 语句测试输入：

-- Function with parameters

function main a: integer returns integer;
   c: integer is 5;
begin
   case a is
      when 1 => 3;
      when 2 => 4;
      others => c;
   endcase;
end;

这是我的 parser.y：

%{

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <math.h>

using namespace std;

#include "values.h"
#include "listing.h"
#include "symbols.h"
#include "stdlib.h"
#include <stdio.h>

int yylex();
void yyerror(const char* message);

Symbols<int> symbols;
double *parameter;
int result;
vector<int> case_statements;

%}

%define parse.error verbose

%union
{
    CharPtr iden;
    Operators oper;
    int value;
}

%token <iden> IDENTIFIER
%token <value> INT_LITERAL REAL_LITERAL BOOL_LITERAL CASE CASES TRUE FALSE ARROW

%token <oper> ADDOP MULOP RELOP EXPOP REMOP NOTOP OROP
%token ANDOP

%token BEGIN_ BOOLEAN END ENDREDUCE FUNCTION INTEGER IS REDUCE RETURNS THEN WHEN ELSE ENDCASE IF ENDIF OTHERS REAL

%type <value> body statement_ statement reductions expression relation term binary factor primary exponent unary case cases
%type <oper> operator

%%

function:   
    function_header optional_variable body {result = $3;} ;
    
function_header:    
    FUNCTION IDENTIFIER parameters RETURNS type ';' |
    FUNCTION IDENTIFIER RETURNS type ';' |
    error ';' ;

optional_variable:
    optional_variable variable |
    error ';' | %empty 
    ;

variable:   
    IDENTIFIER ':' type IS statement_ {symbols.insert($1, $5);} ;

parameters:
    parameter optional_parameter;

optional_parameter:
    optional_parameter ',' parameter | %empty 
    ;

parameter:
    IDENTIFIER ':' type {symbols.insert($1, parameter[0]);} ;

type:
    INTEGER |
    REAL |
    BOOLEAN ;

body:
    BEGIN_ statement_ END ';' {$$ = $2;} ;
    
statement_:
    statement ';' |
    error ';' {$$ = 0;} ;

statement:
    expression |
    REDUCE operator reductions ENDREDUCE {$$ = $3;} |
    IF expression THEN statement_ ELSE statement_ ENDIF {$$ = evaluateIfThen($2, $4, $6); } |
    CASE expression IS cases OTHERS ARROW statement_ ENDCASE
    ;

cases:
    cases case {$$ = $2;} | %empty 
    ;

case:
    WHEN INT_LITERAL ARROW statement_ {$$ = $4;} ;
    

operator:
    ADDOP |
    MULOP |
    RELOP |
    EXPOP ;

reductions:
    reductions statement_ {$$ = evaluateReduction($<oper>0, $1, $2);} |
     %empty {$$ = $<oper>0 == ADD ? 0 : 1;} ;

expression:
    expression OROP binary {$$ = $1 || $3;} |    
    binary ;

binary:
    binary ANDOP relation {$$ = $1 && $3;} |
    relation;

relation:
    relation RELOP term {$$ = evaluateRelational($1, $2, $3);} |
    term ;

term:
    term ADDOP factor {$$ = evaluateArithmetic($1, $2, $3);} |
    factor ;
      
factor:
    factor MULOP primary {$$ = evaluateArithmetic($1, $2, $3);} |
    factor REMOP exponent {$$ = evaluateArithmetic($1, $2, $3);} |
    exponent ;

exponent:
    unary | 
    unary EXPOP exponent {$$ = evaluateArithmetic($1, $2, $3);} ;

unary:
    NOTOP primary {$$ = $2;} |
    primary ;

primary:
    '(' expression ')' {$$ = $2;} |
    INT_LITERAL |
    REAL_LITERAL |
    BOOL_LITERAL |
    IDENTIFIER {if (!symbols.find($1, $$)) appendError(UNDECLARED, $1);} ;

%%

void yyerror(const char* message)
{
    appendError(SYNTAX, message);
}

int main(int argc, char *argv[])    
{
    parameter = new double[argc-1];
    for (int i = 1; i < argc; i++) {
        parameter[i-1] = atof(argv[i]);
        }
    firstLine();
    yyparse();
    if (lastLine() == 0)
        cout << "Result = " << result << endl;
    return 0;
} 

这是我的 values.cc：

#include <string>
#include <vector>
#include <cmath>
#include <iostream>

using namespace std;

#include "values.h"
#include "listing.h"

int evaluateReduction(Operators operator_, int head, int tail)
{
    if (operator_ == ADD)
        return head + tail;
    return head * tail;
}


int evaluateRelational(int left, Operators operator_, int right)
{
    int result;
    switch (operator_)
    {
        case LESS:
            result = (left < right);
            break;
        case LESS_EQUAL:
            result = (left <= right);
            break;
        case GREATER:
            result = (left > right);
            break;
        case GREATER_EQUAL:
            result = (left >= right);
            break;
        case EQUAL:
            result = (left == right);
            break;
        case NOT_EQUAL:
            result = (left != right);
            break;
    }
    return result;
}

int evaluateArithmetic(int left, Operators operator_, int right)
{
    int result;
    switch (operator_)
    {
        case ADD:
            result = (left + right);
            break;
        case MULTIPLY:
            result = (left * right);
            break;
        case SUBTRACT:
            result = (left - right);
            break;
        case DIVIDE:
            result = (left / right);
            break;
        case REM:
            result = (left % right);
            break;
        case EXP:
            result = pow(left, right);
            break;
    }
    return result;
}

int evaluateIfThen(int ifStatement, int resultOne, int resultTwo) {
    if (ifStatement != 0) {
        return resultOne;
    }
    else {
        return resultTwo;
    }
}