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#include <stdio.h>
#include <string.h>
#include <ctype.h>
/* The C Programming Language: 2nd Edition
*
* Exercise 5-18: Make `dcl` recover from input errors.
*
* Notes: The book does a poor job of describing what the reader should
* do here. Given that 5-20 calls for a refactor of `dcl`, my solution
* will simply complain at missing parens and brackets, and silently
* accept semicolons and comments at the end of the input line. Those are
* considered "errors" to the book's version of the program, and so this
* solution will fix them.
*
* This solution does not handle more complex data types such as const,
* static, long ("long long ..."), {un}signed, etc. It also won't handle
* arbitrary parentheses. Really simple stuff.
*/
#define MAXTOKEN 100
#define BUFSIZE 100
enum { NAME, PARENS, BRACKETS, TYPE };
void dcl(void);
void dirdcl(void);
int gettoken(void);
char buf[BUFSIZE];
int bufp = 0;
int tokentype;
char token[MAXTOKEN];
char name[MAXTOKEN];
char datatype[MAXTOKEN];
char out[1000];
int get_line(char *s, int lim);
void dcl(void) {
int ns;
for (ns = 0; gettoken() == '*'; ns++) {
}
dirdcl();
while (ns-- > 0) {
strcat(out, " pointer to");
}
}
void dirdcl(void) {
int type;
if (tokentype == '(') {
dcl();
if (tokentype != ')') {
printf("error: missing )\n");
}
} else if (tokentype == TYPE) {
strcat(datatype, " ");
strcat(datatype, token);
// check again for another type
gettoken();
} else if (tokentype == 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, " array");
strcat(out, token);
strcat(out, " of");
}
}
}
int gettoken(void) {
char *p = token;
while (buf[bufp] == ' ' || buf[bufp] == '\t') {
bufp++;
}
if (buf[bufp] == '/') {
if (buf[bufp + 1] == '/' || buf[bufp + 1] == '*') {
while (buf[bufp] != '\n') {
bufp++;
}
}
return tokentype = buf[bufp];
} else if (buf[bufp] == '(') {
if (buf[++bufp] == ')') {
strcpy(token, "()");
bufp++;
return tokentype = PARENS;
} else {
return tokentype = '(';
}
} else if (buf[bufp] == '[') {
while (buf[bufp] != ']') {
if (buf[bufp + 1] == '[') {
return tokentype = buf[bufp + 1];
}
if (isspace(buf[bufp])) {
bufp++;
continue;
}
*p++ = buf[bufp++];
}
*p++ = buf[bufp++];
*p = '\0';
return tokentype = BRACKETS;
} else if (isalpha(buf[bufp])) {
*p++ = buf[bufp++];
while (isalnum(buf[bufp])) {
*p++ = buf[bufp++];
}
*p = '\0';
/* check types */
if (strcmp(token, "int") == 0 ||
strcmp(token, "double") == 0 ||
strcmp(token, "char") == 0) {
return tokentype = TYPE;
}
return tokentype = NAME;
} else {
return tokentype = buf[bufp++];
}
}
/* Returns length of line including \n
*/
int get_line(char *s, int lim) {
int c, i;
for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; ++i) {
*s++ = c;
}
if (c == '\n') {
*s++ = c;
i++;
}
*s = '\0';
return i;
}
int main(void) {
int len = 0;
while ((len = get_line(buf, BUFSIZE)) > 0 && buf[len - 1] != EOF) {
if (len == 1 && buf[bufp] == '\n') {
continue;
}
bufp = 0;
datatype[0] = 0;
gettoken();
if (tokentype == TYPE) {
strcpy(datatype, token);
}
out[0] = '\0';
name[0] = '\0';
dcl();
if (tokentype == ')') {
printf("error: too many closing parens\n\n");
} else if (tokentype == ']') {
printf("error: too many closing brackets\n\n");
} else if (tokentype == '(') {
printf("error: too many opening parens\n\n");
} else if (tokentype == '[') {
printf("error: too many opening brackets\n\n");
} else {
printf("%s: %s %s\n\n", name, out, datatype);
}
}
return 0;
}
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