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Commit 6564a3d

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Organize the code. Declarations in functions.h, implementation in functions.c and program code in main.c. Also, included Makefile to build the program.
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‎chapter05/5-6/functions.c‎

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#include <ctype.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "functions.h"
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/* atoi: convert s to integer (chapter 3) */
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int atoi(const char *s)
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{
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int n, sign;
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while (isspace(*s)) /* skip whitespace */
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++s;
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sign = (*s == '-') ? -1 : 1;
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if (*s == '+' || *s == '-') /* skip sign */
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++s;
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for (n = 0; isdigit(*s); ++s)
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n = 10 * n + (*s - '0');
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return sign * n;
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}
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/* atof: convert string s to double (chapter 4) */
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double atof(const char *s)
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{
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int sign, expSign;
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double val, power, exponent;
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while (isspace(*s)) /* skip whitespace */
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++s;
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sign = (*s == '-') ? -1 : 1;
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if (*s == '+' || *s == '-')
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++s;
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for (val = 0.0; isdigit(*s); ++s)
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val = 10.0 * val + (*s - '0');
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if (*s == '.')
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++s;
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for (power = 1.0; isdigit(*s); ++s) {
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val = 10.0 * val + (*s - '0');
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power *= 10.0;
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}
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if (tolower(*s) == 'e') /* handle scientific notation */
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++s;
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expSign = (*s == '-') ? -1 : 1; /* record exponent's sign */
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if (*s == '+' || *s == '-')
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++s;
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for (exponent = 0.0; isdigit(*s); s++) /* extract the exponent */
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exponent = 10.0 * exponent + (*s - '0');
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while (exponent-- != 0) /* adjust power according to exponent */
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power = (expSign > 0) ? power / 10: power * 10;
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return sign * val / power;
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}
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/* itoa: convert n to characters in s (chapter 3) */
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void itoa(int n, char *s)
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{
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int sign;
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sign = n; /* record sign */
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do { /* generate digits in reverse order */
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*s++ = abs(n % 10 + '0'); /* get the next digit */
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} while ((n /= 10) > 0); /* delete it */
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if (sign < 0)
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*s++ = '-';
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*s = '0円';
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reverse(s - strlen(s));
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}
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/* getLine function: read a line into s, return length (chapter 4) */
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int getLine(char *s, int lim)
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{
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int c;
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char *len;
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len = s;
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while (--lim > 0 && (c = getchar()) != EOF && c != '\n')
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*s++ = c;
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if (c == '\n')
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*s++ = c;
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*s = '0円';
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return strlen(len);
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}
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/* getop: get next operator or numeric operand (chapter 4) - getch/ungetch version */
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int getop(char *s)
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{
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int c;
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char *var;
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while (isblank(s[0] = c = getchar()))
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;
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s[1] = '0円';
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if (c == '-') /* check sign */
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if (!isdigit(*++s = c = getchar())) {
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ungetc(c, stdin);
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c = *--s; /* not a sign */
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}
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if (isalpha(c)) { /* string command */
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var = s;
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while (isalpha(*++s = c = getchar()))
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;
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*s = '0円';
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ungetc(c, stdin);
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return (strlen(var) == 1) ? var[0] : NAME;
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}
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if (!isdigit(c) && c != '.')
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return c; /* not a number */
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if (isdigit(c))
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while (isdigit(*++s = c = getchar()))
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;
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if( c == '.') /* collect fraction part */
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while (isdigit(*++s = c = getchar()))
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;
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*s = '0円';
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ungetc(c, stdin);
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return NUMBER;
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}
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/* reverse: reverses the string s in place (chapter 3) */
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void reverse(char *s)
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{
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char *p, *q, tmp;
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q = s + strlen(s) - 1;
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for (p = s; p < q; ++p, --q) {
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tmp = *p;
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*p = *q;
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*q = tmp;
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}
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}
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/* strindex: return index of t in s, -1 if none (chapter 4) */
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int strindex(const char *s, const char *t)
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{
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int pos;
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const char *j, *k;
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for (pos = 0; *s; ++s, ++pos) {
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for (j = s, k = t; *k && (*j == *k); ++j, ++k)
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;
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if (k > t && *k == '0円')
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return pos;
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}
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return -1;
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}

‎chapter05/5-6/functions.h‎

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#ifndef FUNCTIONS_H
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#define FUNCTIONS_H
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#include <stddef.h>
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#define NUMBER '0' /* signal that a number was found */
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#define NAME '1' /* signal that a string command was found */
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int atoi(const char *);
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double atof(const char *);
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void itoa(int , char *);
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int getLine(char *, int);
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int getop(char *);
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void reverse(char *);
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int strindex(const char *, const char *);
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#endif /* FUNCTIONS_H */

‎chapter05/5-6/main.c‎

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/*
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* Exercise 5-6. Rewrite appropriate programs from earlier chapters and
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* exercises with pointers instead of array indexing. Good possibilities
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* include getLine (chapter 1 and 4), atoi, itoa, and their variants (Chapters
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* 2, 3 and 4), reverse (Chapter 3), and strindex and gettop (Chapter 4)
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*
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* By Faisal Saadatmand
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*/
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/*
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* Just use any function listed above in main.c to test its code. Below are
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* some examples.
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*
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* Instructions:
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* To Build:
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* make main
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* To run:
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* ./main
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* To clean object files:
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* make clean
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*
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*/
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#include <stdio.h>
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#include "functions.h"
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int main(void)
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{
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char str[] = "It's not personal";
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const char *pattern = "son";
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char str2[] = "5892";
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int pos, number;
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/* strindex */
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if ((pos = strindex(str, pattern)) < 0)
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printf("Not found\n");
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else
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printf("%i\n", pos);
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/* reverse */
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reverse(str);
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printf("%s\n", str);
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/* atoi */
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number = atoi(str2);
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printf("%i\n", number);
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printf("%i\n", atoi("4092"));
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return 0;
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}

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