1.首先准备好实验的小工具，flex.exe bison.exe bison.hairy bison.simple gcc编译器
2.配置实验所需环境：
①配置bison环境：在“我的电脑”-“右键”-“属性”-“高级系统设置”-在菜单栏下选择“高级”
-“环境变量”，在系统变量中添加变量名：BISON_SIMPLE,，变量值为bison.simple的所在路径：
C:\Documents and Settings\Administrator\桌面\exam4\yacc\bison.simple；在添加变量名：
BISON_HAIRY，变量值为：C:\Documents and Settings\Administrator\桌面\exam4\yacc\bison.hairy。
②配置gcc编译器：在安装了Dev-cpp工具后，在环境变量中的Path变量中添加其bin目录，调用
gcc编译器，C:\Dev-Cpp\bin；
工具配置工作完成。
下面我们来举几个例子：
1.calc1.l
/* calculator #1 */
%{
#include "y.tab.h"
#include <stdlib.h>
void yyerror(char *);
%}
%%
[0-9]+ {
yylval = atoi(yytext);
return INTEGER;
}
[-+\n] { return *yytext; }
[ \t] ; /* skip whitespace */
. yyerror("Unknown character");
%%
int yywrap(void) {
return 1;
}
calc2.y
%{
#include <stdio.h>
int yylex(void);
void yyerror(char *);
%}
%token INTEGER
%%
program:
program expr '\n' { printf("%d\n", $2); }
|
;
expr:
INTEGER
| expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
;
%%
void yyerror(char *s) {
fprintf(stderr, "%s\n", s);
}
int main(void) {
yyparse();
return 0;
}
编译命令：
bison -y -d calc1.y
flex calc1.l
gcc -c y.tab.c lex.yy.c
gcc y.tab.o lex.yy.o -o calc1.exe
操作步骤：
|
1.打开运行窗口，输入cmd，在弹出的doc窗口下输入cd flex文件路径，进入文件夹后，编译文件目录下的calc1.l文件，得到一个lex.yy.c文件；再进入bison文件路径，编译calc1.y文件，得到y.tab.c和y.tab.h文件.
得到的文件放在同一目录下，用gcc编译器进行编译，在cmd界面下进入到文件所在路径，输入命令：
gcc –c y.tab.c lex.yy.c，讲两个文件连接起来，得到文件y.tab.o lex.yy.o，再将两个连接的文件编译生成一个exe文件：gcc y.tab.o lex.yy.o -o calc1.exe，得到名为calc1的可执行文件，执行该文件：
calc1.exe；
验证了calc1程序是一个简单的加减计算器。
|
2.
calc2.l
/* calculator #1 */
%{
#include "y.tab.h"
#include <stdlib.h>
void yyerror(char *);
%}
%%
[a-z] {
yylval = *yytext - 'a';
return VARIABLE;
}
[0-9]+ {
yylval = atoi(yytext);
return INTEGER;
}
[-+()=/*\n] { return *yytext; }
[ \t] ; /* skip whitespace */
. yyerror("Unknown character");
%%
int yywrap(void) {
return 1;
}
calc2.y
%{
#include <stdio.h>
void yyerror(char *);
int yylex(void);
int sym[26];
%}
%token INTEGER VARIABLE
%left '+' '-'
%left '*' '/'
%%
program:
program statement '\n'
| /* NULL */
;
statement:
expression { printf("%d\n", $1); }
| VARIABLE '=' expression { sym[$1] = $3; }
;
expression:
INTEGER
| VARIABLE { $$ = sym[$1]; }
| expression '+' expression { $$ = $1 + $3; }
| expression '-' expression { $$ = $1 - $3; }
| expression '*' expression { $$ = $1 * $3; }
| expression '/' expression { $$ = $1 / $3; }
| '(' expression ')' { $$ = $2; }
;
%%
void yyerror(char *s) {
fprintf(stderr, "%s\n", s);
}
int main(void) {
yyparse();
}
编译命令：
bison -y -d calc2.y
flex calc2.l
gcc -c y.tab.c lex.yy.c
gcc y.tab.o lex.yy.o -o calc2.exe
操作步骤与上面的例子相同。
下面这个比较负责一点：
calc3.l
%{
#include <stdlib.h>
#include "calc3.h"
#include "y.tab.h"
void yyerror(char *);
%}
%%
[a-z] {
yylval.sIndex = *yytext - 'a';
return VARIABLE;
}
0 {
yylval.iValue = atoi(yytext);
return INTEGER;
}
[1-9][0-9]* {
yylval.iValue = atoi(yytext);
return INTEGER;
}
[-()<>=+*/;{}.] {
return *yytext;
}
">=" return GE;
"<=" return LE;
"==" return EQ;
"!=" return NE;
"while" return WHILE;
"if" return IF;
"else" return ELSE;
"print" return PRINT;
[ \t\n]+ ; /* ignore whitespace */
. yyerror("Unknown character");
%%
int yywrap(void) {
return 1;
}
calc3.y
%{
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include "calc3.h"
/* prototypes */
nodeType *opr(int oper, int nops, ...);
nodeType *id(int i);
nodeType *con(int value);
void freeNode(nodeType *p);
int ex(nodeType *p);
int yylex(void);
void yyerror(char *s);
int sym[26]; /* symbol table */
%}
%union {
int iValue; /* integer value */
char sIndex; /* symbol table index */
nodeType *nPtr; /* node pointer */
};
%token <iValue> INTEGER
%token <sIndex> VARIABLE
%token WHILE IF PRINT
%nonassoc IFX
%nonassoc ELSE
%left GE LE EQ NE '>' '<'
%left '+' '-'
%left '*' '/'
%nonassoc UMINUS
%type <nPtr> stmt expr stmt_list
%%
program:
function { exit(0); }
;
function:
function stmt { ex($2); freeNode($2); }
| /* NULL */
;
stmt:
';' { $$ = opr(';', 2, NULL, NULL); }
| expr ';' { $$ = $1; }
| PRINT expr ';' { $$ = opr(PRINT, 1, $2); }
| VARIABLE '=' expr ';' { $$ = opr('=', 2, id($1), $3); }
| WHILE '(' expr ')' stmt { $$ = opr(WHILE, 2, $3, $5); }
| IF '(' expr ')' stmt %prec IFX { $$ = opr(IF, 2, $3, $5); }
| IF '(' expr ')' stmt ELSE stmt { $$ = opr(IF, 3, $3, $5, $7); }
| '{' stmt_list '}' { $$ = $2; }
;
stmt_list:
stmt { $$ = $1; }
| stmt_list stmt { $$ = opr(';', 2, $1, $2); }
;
expr:
INTEGER { $$ = con($1); }
| VARIABLE { $$ = id($1); }
| '-' expr %prec UMINUS { $$ = opr(UMINUS, 1, $2); }
| expr '+' expr { $$ = opr('+', 2, $1, $3); }
| expr '-' expr { $$ = opr('-', 2, $1, $3); }
| expr '*' expr { $$ = opr('*', 2, $1, $3); }
| expr '/' expr { $$ = opr('/', 2, $1, $3); }
| expr '<' expr { $$ = opr('<', 2, $1, $3); }
| expr '>' expr { $$ = opr('>', 2, $1, $3); }
| expr GE expr { $$ = opr(GE, 2, $1, $3); }
| expr LE expr { $$ = opr(LE, 2, $1, $3); }
| expr NE expr { $$ = opr(NE, 2, $1, $3); }
| expr EQ expr { $$ = opr(EQ, 2, $1, $3); }
| '(' expr ')' { $$ = $2; }
;
%%
#define SIZEOF_NODETYPE ((char *)&p->con - (char *)p)
nodeType *con(int value) {
nodeType *p;
size_t nodeSize;
/* allocate node */
nodeSize = SIZEOF_NODETYPE + sizeof(conNodeType);
if ((p = malloc(nodeSize)) == NULL)
yyerror("out of memory");
/* copy information */
p->type = typeCon;
p->con.value = value;
return p;
}
nodeType *id(int i) {
nodeType *p;
size_t nodeSize;
/* allocate node */
nodeSize = SIZEOF_NODETYPE + sizeof(idNodeType);
if ((p = malloc(nodeSize)) == NULL)
yyerror("out of memory");
/* copy information */
p->type = typeId;
p->id.i = i;
return p;
}
nodeType *opr(int oper, int nops, ...) {
va_list ap;
nodeType *p;
size_t nodeSize;
int i;
/* allocate node */
nodeSize = SIZEOF_NODETYPE + sizeof(oprNodeType) +
(nops - 1) * sizeof(nodeType*);
if ((p = malloc(nodeSize)) == NULL)
yyerror("out of memory");
/* copy information */
p->type = typeOpr;
p->opr.oper = oper;
p->opr.nops = nops;
va_start(ap, nops);
for (i = 0; i < nops; i++)
p->opr.op[i] = va_arg(ap, nodeType*);
va_end(ap);
return p;
}
void freeNode(nodeType *p) {
int i;
if (!p) return;
if (p->type == typeOpr) {
for (i = 0; i < p->opr.nops; i++)
freeNode(p->opr.op[i]);
}
free (p);
}
void yyerror(char *s) {
fprintf(stdout, "%s\n", s);
}
int main(void) {
yyparse();
return 0;
}
calc3.h
typedef enum { typeCon, typeId, typeOpr } nodeEnum;
/* constants */
typedef struct {
int value; /* value of constant */
} conNodeType;
/* identifiers */
typedef struct {
int i; /* subscript to sym array */
} idNodeType;
/* operators */
typedef struct {
int oper; /* operator */
int nops; /* number of operands */
struct nodeTypeTag *op[1]; /* operands (expandable) */
} oprNodeType;
typedef struct nodeTypeTag {
nodeEnum type; /* type of node */
/* union must be last entry in nodeType */
/* because operNodeType may dynamically increase */
union {
conNodeType con; /* constants */
idNodeType id; /* identifiers */
oprNodeType opr; /* operators */
};
} nodeType;
extern int sym[26];
calc3a.c
#include <stdio.h>
#include "calc3.h"
#include "y.tab.h"
int ex(nodeType *p) {
if (!p) return 0;
switch(p->type) {
case typeCon: return p->con.value;
case typeId: return sym[p->id.i];
case typeOpr:
switch(p->opr.oper) {
case WHILE: while(ex(p->opr.op[0])) ex(p->opr.op[1]); return 0;
case IF: if (ex(p->opr.op[0]))
ex(p->opr.op[1]);
else if (p->opr.nops > 2)
ex(p->opr.op[2]);
return 0;
case PRINT: printf("%d\n", ex(p->opr.op[0])); return 0;
case ';': ex(p->opr.op[0]); return ex(p->opr.op[1]);
case '=': return sym[p->opr.op[0]->id.i] = ex(p->opr.op[1]);
case UMINUS: return -ex(p->opr.op[0]);
case '+': return ex(p->opr.op[0]) + ex(p->opr.op[1]);
case '-': return ex(p->opr.op[0]) - ex(p->opr.op[1]);
case '*': return ex(p->opr.op[0]) * ex(p->opr.op[1]);
case '/': return ex(p->opr.op[0]) / ex(p->opr.op[1]);
case '<': return ex(p->opr.op[0]) < ex(p->opr.op[1]);
case '>': return ex(p->opr.op[0]) > ex(p->opr.op[1]);
case GE: return ex(p->opr.op[0]) >= ex(p->opr.op[1]);
case LE: return ex(p->opr.op[0]) <= ex(p->opr.op[1]);
case NE: return ex(p->opr.op[0]) != ex(p->opr.op[1]);
case EQ: return ex(p->opr.op[0]) == ex(p->opr.op[1]);
}
}
return 0;
}
calc3b.c
#include <stdio.h>
#include "calc3.h"
#include "y.tab.h"
static int lbl;
int ex(nodeType *p) {
int lbl1, lbl2;
if (!p) return 0;
switch(p->type) {
case typeCon:
printf("\tpush\t%d\n", p->con.value);
break;
case typeId:
printf("\tpush\t%c\n", p->id.i + 'a');
break;
case typeOpr:
switch(p->opr.oper) {
case WHILE:
printf("L%03d:\n", lbl1 = lbl++);
ex(p->opr.op[0]);
printf("\tjz\tL%03d\n", lbl2 = lbl++);
ex(p->opr.op[1]);
printf("\tjmp\tL%03d\n", lbl1);
printf("L%03d:\n", lbl2);
break;
case IF:
ex(p->opr.op[0]);
if (p->opr.nops > 2) {
/* if else */
printf("\tjz\tL%03d\n", lbl1 = lbl++);
ex(p->opr.op[1]);
printf("\tjmp\tL%03d\n", lbl2 = lbl++);
printf("L%03d:\n", lbl1);
ex(p->opr.op[2]);
printf("L%03d:\n", lbl2);
} else {
/* if */
printf("\tjz\tL%03d\n", lbl1 = lbl++);
ex(p->opr.op[1]);
printf("L%03d:\n", lbl1);
}
break;
case PRINT:
ex(p->opr.op[0]);
printf("\tprint\n");
break;
case '=':
ex(p->opr.op[1]);
printf("\tpop\t%c\n", p->opr.op[0]->id.i + 'a');
break;
case UMINUS:
ex(p->opr.op[0]);
printf("\tneg\n");
break;
default:
ex(p->opr.op[0]);
ex(p->opr.op[1]);
switch(p->opr.oper) {
case '+': printf("\tadd\n"); break;
case '-': printf("\tsub\n"); break;
case '*': printf("\tmul\n"); break;
case '/': printf("\tdiv\n"); break;
case '<': printf("\tcompLT\n"); break;
case '>': printf("\tcompGT\n"); break;
case GE: printf("\tcompGE\n"); break;
case LE: printf("\tcompLE\n"); break;
case NE: printf("\tcompNE\n"); break;
case EQ: printf("\tcompEQ\n"); break;
}
}
}
return 0;
}
calc3g.c
/* source code courtesy of Frank Thomas Braun */
/* calc3d.c: Generation of the graph of the syntax tree */
#include <stdio.h>
#include <string.h>
#include "calc3.h"
#include "y.tab.h"
int del = 1; /* distance of graph columns */
int eps = 3; /* distance of graph lines */
/* interface for drawing (can be replaced by "real" graphic using GD or other) */
void graphInit (void);
void graphFinish();
void graphBox (char *s, int *w, int *h);
void graphDrawBox (char *s, int c, int l);
void graphDrawArrow (int c1, int l1, int c2, int l2);
/* recursive drawing of the syntax tree */
void exNode (nodeType *p, int c, int l, int *ce, int *cm);
/*****************************************************************************/
/* main entry point of the manipulation of the syntax tree */
int ex (nodeType *p) {
int rte, rtm;
graphInit ();
exNode (p, 0, 0, &rte, &rtm);
graphFinish();
return 0;
}
/*c----cm---ce----> drawing of leaf-nodes
l leaf-info
*/
/*c---------------cm--------------ce----> drawing of non-leaf-nodes
l node-info
* |
* ------------- ...----
* | | |
* v v v
* child1 child2 ... child-n
* che che che
*cs cs cs cs
*
*/
void exNode
( nodeType *p,
int c, int l, /* start column and line of node */
int *ce, int *cm /* resulting end column and mid of node */
)
{
int w, h; /* node width and height */
char *s; /* node text */
int cbar; /* "real" start column of node (centred above subnodes) */
int k; /* child number */
int che, chm; /* end column and mid of children */
int cs; /* start column of children */
char word[20]; /* extended node text */
if (!p) return;
strcpy (word, "???"); /* should never appear */
s = word;
switch(p->type) {
case typeCon: sprintf (word, "c(%d)", p->con.value); break;
case typeId: sprintf (word, "id(%c)", p->id.i + 'A'); break;
case typeOpr:
switch(p->opr.oper){
case WHILE: s = "while"; break;
case IF: s = "if"; break;
case PRINT: s = "print"; break;
case ';': s = "[;]"; break;
case '=': s = "[=]"; break;
case UMINUS: s = "[_]"; break;
case '+': s = "[+]"; break;
case '-': s = "[-]"; break;
case '*': s = "[*]"; break;
case '/': s = "[/]"; break;
case '<': s = "[<]"; break;
case '>': s = "[>]"; break;
case GE: s = "[>=]"; break;
case LE: s = "[<=]"; break;
case NE: s = "[!=]"; break;
case EQ: s = "[==]"; break;
}
break;
}
/* construct node text box */
graphBox (s, &w, &h);
cbar = c;
*ce = c + w;
*cm = c + w / 2;
/* node is leaf */
if (p->type == typeCon || p->type == typeId || p->opr.nops == 0) {
graphDrawBox (s, cbar, l);
return;
}
/* node has children */
cs = c;
for (k = 0; k < p->opr.nops; k++) {
exNode (p->opr.op[k], cs, l+h+eps, &che, &chm);
cs = che;
}
/* total node width */
if (w < che - c) {
cbar += (che - c - w) / 2;
*ce = che;
*cm = (c + che) / 2;
}
/* draw node */
graphDrawBox (s, cbar, l);
/* draw arrows (not optimal: children are drawn a second time) */
cs = c;
for (k = 0; k < p->opr.nops; k++) {
exNode (p->opr.op[k], cs, l+h+eps, &che, &chm);
graphDrawArrow (*cm, l+h, chm, l+h+eps-1);
cs = che;
}
}
/* interface for drawing */
#define lmax 200
#define cmax 200
char graph[lmax][cmax]; /* array for ASCII-Graphic */
int graphNumber = 0;
void graphTest (int l, int c)
{ int ok;
ok = 1;
if (l < 0) ok = 0;
if (l >= lmax) ok = 0;
if (c < 0) ok = 0;
if (c >= cmax) ok = 0;
if (ok) return;
printf ("\n+++error: l=%d, c=%d not in drawing rectangle 0, 0 ... %d, %d",
l, c, lmax, cmax);
exit (1);
}
void graphInit (void) {
int i, j;
for (i = 0; i < lmax; i++) {
for (j = 0; j < cmax; j++) {
graph[i][j] = ' ';
}
}
}
void graphFinish() {
int i, j;
for (i = 0; i < lmax; i++) {
for (j = cmax-1; j > 0 && graph[i][j] == ' '; j--);
graph[i][cmax-1] = 0;
if (j < cmax-1) graph[i][j+1] = 0;
if (graph[i][j] == ' ') graph[i][j] = 0;
}
for (i = lmax-1; i > 0 && graph[i][0] == 0; i--);
printf ("\n\nGraph %d:\n", graphNumber++);
for (j = 0; j <= i; j++) printf ("\n%s", graph[j]);
printf("\n");
}
void graphBox (char *s, int *w, int *h) {
*w = strlen (s) + del;
*h = 1;
}
void graphDrawBox (char *s, int c, int l) {
int i;
graphTest (l, c+strlen(s)-1+del);
for (i = 0; i < strlen (s); i++) {
graph[l][c+i+del] = s[i];
}
}
void graphDrawArrow (int c1, int l1, int c2, int l2) {
int m;
graphTest (l1, c1);
graphTest (l2, c2);
m = (l1 + l2) / 2;
while (l1 != m) { graph[l1][c1] = '|'; if (l1 < l2) l1++; else l1--; }
while (c1 != c2) { graph[l1][c1] = '-'; if (c1 < c2) c1++; else c1--; }
while (l1 != l2) { graph[l1][c1] = '|'; if (l1 < l2) l1++; else l1--; }
graph[l1][c1] = '|';
}
编译命令：
bison -y -d calc3.y
flex calc3.l
gcc -c y.tab.c lex.yy.c
gcc y.tab.o lex.yy.o calc3a.c -o calc3a.exe
gcc y.tab.o lex.yy.o calc3b.c -o calc3b.exe
gcc y.tab.o lex.yy.o calc3g.c -o calc3g.exe
生成树版本结果：
解析版本结果：
评论