dclΒΆ

dcl.c

/* DCL:  A Recursive Descent Parser */

/* dcl: parse a declarator */

void dcl(void)
{
    int ns;
    
    for(ns=0;gettoken()=='*';) /* count *'s */
        ns++;
    
    dirdcl();
    while(ns-- > 0)
        strcat(out,"pointer to");
}

/* dirdcl: parse a direct declarator */

void dirdcl(void)
{
    int type;
    
    if(tokentype == '(')    /* dcl */
    {
        dcl();
        
        if(tokentype != ')')
            printf("error: missing ) \n");
    }
    else if(tokentype == NAME)  /* variable name */
        strcpy(name,token);
    else
        printf("error: expected name or (dcl) \n");
    
    while((type=gettoken()) == PARENS || type == BRACKETS )
        if(type = PARENS)
                strcat(out,"function returning");
        else
        {
            strcat(out,"arg");
            strcat(out,token);
            strcat(out,"of");
        }
}


#include<stdio.h>
#include<string.h>
#include<ctype.h>

#define MAXTOKEN 100

enum {NAME,PARENS,BRACKETS};

void dcl(void);
void directdcl(void);
int gettoken(void);
int tokentype;          /* type of last token */
char token[MAXTOKEN];       /* last token string */
char name[MAXTOKEN];        /* identifier name */
char datatype[MAXTOKEN];    /* data type=char, int etc */
char out[1000];         /* output string */

int main(void)
{
    while(gettoken()!=EOF)
    {
        strcpy(datatype,token);
        out[0]='\0';
        dcl();
    
    if(tokentype != '\n')
        printf("syntax error \n");
    
    printf(" %s %s %s \n",name,out,datatype);
    }
    
return 0;
}

int gettoken(void)
{
    int i,getch(void);
    void ungetch(int);
    char *p = token;

    while((c=getch()) == ' ' || c == '\t')
        ;
    
    if( c == '(')
    {
        if((c=getch()) == ')')
        {
            strcpy(token,"()");
            return tokentype = PARENS;
        }
        else
        {
            ungetch(c);
            return tokentype = '(';
        }
    else if ( c == '[')
    {
        for(*p++ = c; (*p++ = getch()) != ']';)
            ;
        *p = '\0';
        return tokentype = BRACKETS;
    }
    else if ( isalpha(c))
    {
        for(*p++ =c; isalnum(c=getch());)
            *p++ = c;
        *p = '\0';
        ungetch(c);
        return tokentype = NAME;
    }
    else
        return tokentype =c;
}

#define BUFSIZE  100

char buf[BUFSIZE];          /* buffer for ungetch */
int bufp = 0;               /* next free position in buf */

int getch(void)             /* get a (possibly pushed back) character */
{
    return (bufp > 0) ? buf[--bufp]:getchar();
}

void ungetch(int c)     /* push a character back on input */
{
    if(bufp >= BUFSIZE)
        printf("ungetch: too many characters \n");
    else
        buf[bufp++] = c;
}





















    

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