5.2

Author: Heatwave

chapter-5-pointers-and-arrays/1.pointer.c

@@ -0,0 +1,12 @@
+int main()
+{
+	int x = 1, y = 2, z[10];
+	int *ip;
+
+	ip = &x;
+	y = *ip;
+	*ip = 0;
+	ip = &z[0];
+	
+	return 0;
+}

chapter-5-pointers-and-arrays/2.swap.c

@@ -0,0 +1,13 @@
+int main()
+{
+}
+
+void swap(int *px, int *py)
+{
+	int temp;
+
+	temp = *px;
+	*px = *py;
+	*py = temp;
+}
+

chapter-5-pointers-and-arrays/3.getint.c

@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <ctype.h>
+
+#define SIZE 10
+
+int getch(void);
+void ungetch(int);
+
+// compile with getch.c
+int main()
+{
+	int n, array[SIZE], getint(int *);
+
+	for (n = 0; n < SIZE; n++)
+		array[n] = 0;
+	
+	for (n = 0; n < SIZE && getint(&array[n]) != EOF; n++)
+		;
+	
+	for (n = 0; n < SIZE; n++)
+		printf("%d ", array[n]);
+
+	printf("\n");
+	return 0;
+}
+
+int getint(int *pn)
+{
+	int c, sign;
+
+	while (isspace(c = getch()))
+		;
+	
+	if (!isdigit(c) && c != EOF && c != '+' && c != '-') {
+		ungetch(c);
+		return 0;
+	}
+	sign = (c == '-') ? -1 : 1;
+	if (c == '+' || c == '-') {
+		c = getch();
+		if (!isdigit(c)) {
+			ungetch(sign == 1 ? '+' : '-');
+			return 0;
+		}
+	}
+	for (*pn = 0; isdigit(c); c = getch())
+		*pn = 10 * *pn + (c - '0');
+	*pn *= sign;
+	if (c != EOF)
+		ungetch(c);
+	return c;
+}

chapter-5-pointers-and-arrays/4.getfloat.c

@@ -0,0 +1,89 @@
+#include <stdio.h>
+#include <ctype.h>
+
+#define SIZE 10
+
+int getch(void);
+void ungetch(int);
+
+// compile with getch.c
+int main()
+{
+	int n;
+	double array[SIZE], getfloat(double *);
+	
+	for (n = 0; n < SIZE; n++)
+		array[n] = 0.0;
+
+	for (n = 0; n < SIZE && getfloat(&array[n]) != EOF; n++)
+		;
+
+	for (n = 0; n < SIZE; n++)
+		printf("%g ", array[n]);
+
+	printf("\n");
+	return 0;
+}
+
+double getfloat(double *pn)
+{
+	int c, sign;
+	double power;
+
+	while (isspace(c = getch()))
+		;
+
+	if (!isdigit(c) && c != EOF && c != '+' && c != '-' && c != '.') {
+		ungetch(c);
+		return 0.0;
+	}
+	sign = (c == '-') ? -1 : 1;
+	if (c == '+' || c == '-') {
+		c = getch();
+		if (!isdigit(c) && c != '.') {
+			ungetch(sign == 1 ? '+' : '-');
+			return 0.0;
+		}
+	}
+	for (*pn = 0.0; isdigit(c); c = getch())
+		*pn = 10.0 * *pn + (c - '0');
+
+	if (c == '.') {
+		c = getch();
+	}
+	
+	for (power = 1.0; isdigit(c); c = getch()) {
+		*pn = 10.0 * *pn + (c - '0');
+		power *= 10.0;
+	}
+
+	int eSign = 1;
+	if (c == 'e' || c == 'E') {
+		c = getch();
+		if (c == '-') {
+			eSign = -1;
+			c = getch();
+		} else if (c == '+') {
+			c = getch();
+		}
+	}
+
+	double ePower = 1.0;
+	int eCount = 0;
+	for (eCount = 0; isdigit(c); c = getch()) 
+		eCount = 10.0 * eCount + (c - '0');
+
+	while (eCount-- > 0)
+		ePower *= 10;
+
+	*pn = *pn / power * sign;
+
+	if (eSign > 0)
+		*pn *= ePower;
+	else
+		*pn /= ePower;
+
+	if (c != EOF)
+		ungetch(c);
+	return c;
+}

chapter-5-pointers-and-arrays/getch.c

@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <string.h>
+
+#define BUFSIZE 100
+
+int buf[BUFSIZE];
+int bufp = 0;
+
+int value = EOF;
+
+int getch(void)
+{
+	return (bufp > 0) ? buf[--bufp] : getchar();
+}
+
+void ungetch(int c)
+{
+	if (bufp >= BUFSIZE)
+		printf("ungetch: too many characters\n");
+	else
+		buf[bufp++] = c;
+}
+
+void ungetchs(char s[])
+{
+	int len = strlen(s);
+	while (len > 0) {
+		ungetch(s[--len]);
+	}
+}
+
+int getchOne(void)
+{
+	if (value != EOF) {
+		int temp = value;
+		value = EOF;
+		return temp;
+	}
+	else
+		return getchar();
+}
+
+void ungetchOne(int c)
+{
+	if (value != EOF)
+		printf("ungetchOne: cannot ungetch more char\n");
+	else
+		value = c;
+}