kdeng00
3c78e25b36
Working on exercise 6.1. Setting up the code before starting. Functions are being used that were deinfed in earlier chapters - chapter 4.
129 lines
2.3 KiB
C
129 lines
2.3 KiB
C
/*
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*
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* Exercise 6-1. Our version of getword does not properly handle underscores,
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* string constants, comments, or preprocessor control lines. Write a
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* better version.
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*
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* Author: Kun Deng
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*/
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#include <stdio.h>
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#include <ctype.h>
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#include <string.h>
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#include <stddef.h>
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#define BUFFSIZE 100
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#define MAXWORD 100
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#define NKEYS (sizeof keytab / sizeof(struct key))
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char buf[BUFFSIZE];
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int bufp = 0;
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struct key {
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char *word;
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int count;
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};
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/*
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struct key {
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char *word;
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int count;
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} keytab[NKEYS];
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*/
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struct key keytab[] = {
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"auto", 0,
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"break", 0,
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};
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/* getword: get next word or character from input */
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int getword(char *word, int lim);
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/* binsearch: find word in tab[0]...tab[n-1] */
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struct key *binsearch(char *word, struct key *tab, int n);
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/* get a (possibly pushed back) character */
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int getch(void);
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/* push character back on input */
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void ungetch(int c);
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int getword(char *word, int lim) {
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int c, getch(void);
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void ungetch(int);
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char *w = word;
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while (isspace(c = getch()));
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if (c != EOF)
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*w++ = c;
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if (!isalpha(c)) {
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*w = '\0';
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return 0;
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}
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for (; --lim > 0; w++)
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if (!isalnum(*w = getch())) {
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ungetch(*w);
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break;
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}
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*w = '\0';
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return word[0];
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}
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struct key *binsearch(char *word, struct key *tab, int n) {
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int cond;
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struct key *low = &tab[0];
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struct key *high = &tab[n];
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struct key *mid;
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while (low < high) {
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mid = low + (high-low) / 2;
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if ((cond = strcmp(word, mid->word)) < 0 )
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high = mid;
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else if (cond > 0 )
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low = mid + 1;
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else
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return mid;
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}
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return NULL;
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}
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int getch(void) {
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return (bufp > 0) ? buf[--bufp] : getchar();
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}
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/* push character back on input */
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void ungetch(int c) {
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if (bufp >= BUFFSIZE)
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printf("ungetch: too many characters\n");
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else
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buf[bufp++] = c;
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}
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int main()
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{
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int n;
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char word[MAXWORD];
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struct key *p;
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while (getword(word, MAXWORD) != EOF)
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if (isalpha(word[0]))
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if ((p = binsearch(word, keytab, NKEYS)) >= 0)
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p->count++;
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for (p = 0; p < keytab + NKEYS; p++)
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if (p->count > 0)
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printf("%4d %s\n", p->count, p->word);
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return 0;
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}
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