1、编译步骤
- vim lexical.lex
- flex lexical.lex //生成lex.yy.c文件
- gcc -o lexical.exe lex.yy.c -lfl //生成可执行文件 -lfl链接flex的库函数
- touch test.txt //创建测试文件
- //选择一：使用文件读写
- vim test.txt //写入要测试的语句
- touch out.txt //结果输出到该文件里
- ./lexical.exe test.txt out.txt //运行程序
- cat out.txt //查看结果
- //选择二：直接运行程序边写边分析
- ./lexical.exe
vim lexical.lex
flex lexical.lex //生成lex.yy.c文件
gcc -o lexical.exe lex.yy.c -lfl //生成可执行文件 -lfl链接flex的库函数
touch test.txt //创建测试文件
//选择一：使用文件读写
vim test.txt //写入要测试的语句
touch out.txt //结果输出到该文件里
./lexical.exe test.txt out.txt //运行程序
cat out.txt //查看结果
//选择二：直接运行程序边写边分析
./lexical.exe
2、程序源码
- lexical.lex
%{
#include<stdio.h>
#define LT 1
#define LE 2
#define GT 3
#define GE 4
#define EQ 5
#define ADD 6
#define DEC 7
#define MUL 8
#define DIV 9
#define SEM 10
#define LB 11
#define RB 12
#define BLB 13
#define BRB 14
#define WHILE 18
#define DO 19
#define IF 20
#define THEN 21
#define ELSE 22
#define FOR 23
#define ID 24
#define NUMBER 25
#define REAL8 26
#define REAL10 27
#define REAL16 28
#define INT8 29
#define INT10 30
#define INT16 31
#define NEWLINE 40
#define ERRORCHAR 41
int yylval;
%}
delim [ \t\n]
whitespace {delim}+
digit [0-9]
letter [A-Za-z_]
id {letter}({letter}|{digit})*
number {digit}+(\.{digit}+)?([eE][+-]?{digit}+)?
int8 (0([0-7])+)
int10 ([1-9]|[1-9]([0-9])+|0)
int16 (0[xX]([A-Fa-f0-9])+)
real8 (0([0-7])+\.([0-7])*)
real10 (([1-9]|[1-9]([0-9])+)\.[0-9]+|0\.([0-9])+)
real16 0[xX]([A-Fa-f0-9])+\.([A-Fa-f0-9])*
%%
{whitespace} {;}
(while|WHILE) {return (WHILE);}
(do|DO) {return (DO);}
(if|IF) {return (IF);}
(then|THEN) {return (THEN);}
(else|ELSE) {return (ELSE);}
(for|FOR) {return (FOR);}
{id} {return (ID);}
{int8} {return (INT8);}
{int10} {return (INT10);}
{int16} {return (INT16);}
{real8} {return (REAL8);}
{real10} {return (REAL10);}
{real16} {return (REAL16);}
"<" {return (LT);}
"<=" {return (LE);}
">" {return (GT);}
">=" {return (GE);}
"=" {return (EQ);}
"+" {return (ADD);}
"-" {return (DEC);}
"*" {return (MUL);}
"/" {return (DIV);}
";" {return (SEM);}
"(" {return (LB);}
")" {return (RB);}
"{" {return (BLB);}
"}" {return (BRB);}
. {return (ERRORCHAR);}
%%
int yywrap(){
return 1;
}
void writeout(int c){
switch(c){
case ERRORCHAR:fprintf(yyout,"(ERRORCHAR,\"%s\")",yytext);
break;
case INT10:fprintf(yyout,"(INT10,\"%s\")",yytext);
break;
case INT16:fprintf(yyout,"(INT16,\"%s\")",yytext);
break;
case INT8:fprintf(yyout,"(INT8,\"%s\")",yytext);
break;
case WHILE:fprintf(yyout,"(WHILE,\"%s\")",yytext);
break;
case DO:fprintf(yyout,"(DO,\"%s\")",yytext);
break;
case IF:fprintf(yyout,"(IF,\"%s\")",yytext);
break;
case THEN:fprintf(yyout,"(THEN,\"%s\")",yytext);
break;
case ELSE:fprintf(yyout,"(ELSE,\"%s\")",yytext);
break;
case FOR:fprintf(yyout,"(FOR,\"%s\")",yytext);
break;
case ID:fprintf(yyout,"(ID,\"%s\")",yytext);
break;
//case NUMBER:fprintf(yyout,"(NUMBER,\"%s\")",yytext);
// break;
case RB:fprintf(yyout,"(RB,\"%s\")",yytext);
break;
case LB:fprintf(yyout,"(LB,\"%s\")",yytext);
break;
case SEM:fprintf(yyout,"(SEM,\"%s\")",yytext);
break;
case DIV:fprintf(yyout,"(DIV,\"%s\")",yytext);
break;
case MUL:fprintf(yyout,"(MUL,\"%s\")",yytext);
break;
case DEC:fprintf(yyout,"(DEC,\"%s\")",yytext);
break;
case ADD:fprintf(yyout,"(ADD,\"%s\")",yytext);
break;
case EQ:fprintf(yyout,"(EQ,\"%s\")",yytext);
break;
case GE:fprintf(yyout,"(GE,\"%s\")",yytext);
break;
case GT:fprintf(yyout,"(GT,\"%s\")",yytext);
break;
case LE:fprintf(yyout,"(LE,\"%s\")",yytext);
break;
case LT:fprintf(yyout,"(LT,\"%s\")",yytext);
break;
case BLB:fprintf(yyout,"(BLB,\"%s\")",yytext);
break;
case BRB:fprintf(yyout,"(BRB,\"%s\")",yytext);
break;
case NEWLINE:fprintf(yyout,"\n");
break;
case REAL8:fprintf(yyout,"(REAL8,\"%s\")",yytext);
break;
case REAL10:fprintf(yyout,"(REAL10,\"%s\")",yytext);
break;
case REAL16:fprintf(yyout,"(REAL16,\"%s\")",yytext);
break;
default:break;
}
return;
}
int main(int argc,char ** argv){
int c,j=0;
if(argc>=2){
if((yyin=fopen(argv[1],"r"))==NULL){
printf("Can't open file %s\n",argv[1]);
return 1;
}
if(argc>=3){
yyout=fopen(argv[2],"w");
}
}
while(c=yylex()){
writeout(c);
j++;
if(j%5==0)
writeout(NEWLINE);
}
if(argc>=2){
fclose(yyin);
if(argc>=3)
fclose(yyout);
}
return 0;
}
3、测试及输出文件
-
test.txt
0 92+data> 0x3f 00 while a+acc>xx do x=x-1; a=6.2+a*0X88.80; if a>b then a=b else a=b-1+c; -
out.txt
(INT10,"0")(INT10,"92")(ADD,"+")(ID,"data")(GT,">") (INT16,"0x3f")(INT8,"00")(WHILE,"while")(ID,"a")(ADD,"+") (ID,"acc")(GT,">")(ID,"xx")(DO,"do")(ID,"x") (EQ,"=")(ID,"x")(DEC,"-")(INT10,"1")(SEM,";") (ID,"a")(EQ,"=")(REAL10,"6.2")(ADD,"+")(ID,"a") (MUL,"*")(REAL16,"0X88.80")(SEM,";")(IF,"if")(ID,"a") (GT,">")(ID,"b")(THEN,"then")(ID,"a")(EQ,"=") (ID,"b")(ELSE,"else")(ID,"a")(EQ,"=")(ID,"b") (DEC,"-")(INT10,"1")(ADD,"+")(ID,"c")(SEM,";")
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