initial commit

Organize the code. Declarations in functions.h, implementation in
functions.c and program code in main.c. Also, included Makefile to build
the program.

Author: fsaadatmand

chapter05/5-6/functions.c

@@ -0,0 +1,145 @@
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "functions.h"
+
+/* atoi: convert s to integer (chapter 3) */
+int atoi(const char *s)
+{
+	int n, sign;
+
+	while (isspace(*s)) /* skip whitespace */
+		++s;
+	sign = (*s == '-') ? -1 : 1;
+	if (*s == '+' || *s == '-') /* skip sign */
+		++s;
+	for (n = 0; isdigit(*s); ++s)
+		n = 10 * n + (*s - '0');
+	return sign * n;
+}
+
+/* atof: convert string s to double (chapter 4) */
+double atof(const char *s)
+{
+	int sign, expSign;
+	double val, power, exponent;
+
+	while (isspace(*s)) /* skip whitespace */
+		++s;
+	sign = (*s == '-') ? -1 : 1;
+	if (*s == '+' || *s == '-')
+		++s;
+	for (val = 0.0; isdigit(*s); ++s)
+		val = 10.0 * val + (*s - '0');
+	if (*s == '.')
+		++s;
+	for (power = 1.0; isdigit(*s); ++s) {
+		val = 10.0 * val + (*s - '0');
+		power *= 10.0;
+	}
+	if (tolower(*s) == 'e') /* handle scientific notation */
+		++s;
+	expSign = (*s == '-') ? -1 : 1; /* record  exponent's sign */
+	if (*s == '+' || *s == '-')
+		++s;
+	for (exponent = 0.0; isdigit(*s); s++) /* extract the exponent */
+		exponent = 10.0 * exponent + (*s - '0');
+	while (exponent-- != 0) /* adjust power according to exponent */
+		power = (expSign > 0) ? power / 10: power * 10; 
+	return sign * val / power;
+}
+
+/* itoa: convert n to characters in s (chapter 3) */
+void itoa(int n, char *s)
+{
+	int sign;
+
+	sign = n; /* record sign */
+
+	do {    /* generate digits in reverse order */
+		*s++ = abs(n % 10 + '0'); /* get the next digit */
+	} while ((n /= 10) > 0); /* delete it */
+	if (sign < 0)
+		*s++ = '-';
+	*s = '\0';
+	reverse(s - strlen(s));
+}
+
+/* getLine function: read a line into s, return length (chapter 4) */
+int getLine(char *s, int lim)
+{
+	int c;
+	char *len;
+
+	len = s;
+	while (--lim > 0 && (c = getchar()) != EOF && c != '\n')
+		*s++ = c;
+	if (c == '\n')
+		*s++ = c;
+	*s = '\0';
+	return strlen(len);
+}
+
+/* getop: get next operator or numeric operand (chapter 4) - getch/ungetch version */
+int getop(char *s)
+{
+	int c;
+	char *var;
+
+	while (isblank(s[0] = c = getchar()))
+		;
+	s[1] = '\0';
+	if (c == '-') /* check sign */
+		if (!isdigit(*++s = c = getchar())) {
+			ungetc(c, stdin);                    
+			c = *--s; /* not a sign */
+		}
+	if (isalpha(c)) { /* string command */
+		var = s;
+		while (isalpha(*++s = c = getchar()))
+			;
+		*s = '\0';
+		ungetc(c, stdin);
+		return (strlen(var) == 1) ? var[0] : NAME;
+	}
+	if (!isdigit(c) && c != '.')
+		return c; /* not a number */
+	if (isdigit(c))
+		while (isdigit(*++s = c = getchar()))
+			;
+	if( c == '.') /* collect fraction part */
+		while (isdigit(*++s = c = getchar()))
+			;
+	*s = '\0';
+	ungetc(c, stdin);
+	return NUMBER;
+}
+
+/* reverse: reverses the string s in place (chapter 3) */
+void reverse(char *s)
+{
+	char *p, *q, tmp;
+
+	q = s + strlen(s) - 1;
+	for (p = s; p < q; ++p, --q) {
+		tmp = *p;
+		*p = *q;
+		*q = tmp;
+	}
+}
+
+/* strindex: return index of t in s, -1 if none (chapter 4) */
+int strindex(const char *s, const char *t)
+{
+	int pos;
+	const char *j, *k;
+
+	for (pos = 0; *s; ++s, ++pos) {
+		for (j = s, k = t; *k && (*j == *k); ++j, ++k)
+			;
+		if (k > t && *k == '\0')
+			return pos;
+	}
+	return -1;
+}

chapter05/5-6/functions.h

@@ -0,0 +1,17 @@
+#ifndef FUNCTIONS_H
+#define FUNCTIONS_H
+
+#include <stddef.h>
+
+#define NUMBER   '0' /* signal that a number was found */
+#define NAME     '1' /* signal that a string command was found */
+
+int atoi(const char *);
+double atof(const char *);
+void itoa(int , char *);
+int getLine(char *, int);
+int getop(char *);
+void reverse(char *);
+int strindex(const char *, const char *);
+
+#endif /* FUNCTIONS_H */

chapter05/5-6/main.c

@@ -0,0 +1,48 @@
+/*
+ * Exercise 5-6. Rewrite appropriate programs from earlier chapters and
+ * exercises with pointers instead of array indexing. Good possibilities
+ * include getLine (chapter 1 and 4), atoi, itoa, and their variants (Chapters
+ * 2, 3 and 4), reverse (Chapter 3), and strindex and gettop (Chapter 4)
+ *
+ * By Faisal Saadatmand
+ */
+
+/*
+ * Just use any function listed above in main.c to test its code. Below are
+ * some examples.
+ *
+ * Instructions:
+ * To Build:
+ * 		make main
+ * To run:
+ * 		./main
+ * To clean object files:
+ * 		make clean
+ *
+ */
+
+#include <stdio.h>
+#include "functions.h"
+
+
+int main(void)
+{
+	char str[] = "It's not personal";
+	const char *pattern = "son";
+	char str2[] = "5892";
+	int pos, number; 
+
+	/* strindex */
+	if ((pos = strindex(str, pattern)) < 0)
+		printf("Not found\n");
+	else
+		printf("%i\n", pos);
+	/* reverse */
+	reverse(str);
+	printf("%s\n", str);
+	/* atoi */
+	number = atoi(str2);
+	printf("%i\n", number);
+	printf("%i\n", atoi("4092"));
+	return 0;
+}