3.4

Author: Heatwave

chapter-3-control-flow/2.switch.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+
+main()
+{
+	int c, i, nwhite, nother, ndigit[10];
+
+	nwhite = nother = 0;
+	for (i = 0; i < 10; i++)
+		ndigit[i] = 0;
+	
+	while ((c = getchar()) != EOF) {
+		switch(c) {
+		case '0': case '1': case '2': case '3': case '4': 
+		case '5': case '6': case '7': case '8': case '9': 
+			ndigit[c-'0']++;
+			break;
+		case ' ':
+		case '\n':
+		case '\t':
+			nwhite++;
+			break;
+		default:
+			nother++;
+			break;
+		}
+	}
+	printf("digits = ");
+	for (i = 0; i < 10; i++)
+		printf(" %d", ndigit[i]);
+	printf(", white space = %d, other = %d\n",
+		nwhite, nother);
+	return 0;
+}

chapter-3-control-flow/3.escape.c

@@ -0,0 +1,56 @@
+#include <stdio.h>
+
+#define MAX_LEN 1000
+
+void escape(char[], char[]);
+
+main()
+{
+	char t[] = "Hello\tWorld\r\n\v";
+	printf("%s\n", t);
+	char s[MAX_LEN];
+	escape(s, t);
+	printf("%s\n", s);
+}
+
+void escape(char s[], char t[])
+{
+	int i, j, n;
+	for (i = 0, j = 0; t[j] != '\0'; i++, j++) {
+		switch(t[j]) {
+			case '\a':
+				s[i++] = '\\';
+				n = 'a';
+				break;
+			case '\b':
+				s[i++] = '\\';
+				n = 'b';
+				break;
+			case '\f':
+				s[i++] = '\\';
+				n = 'f';
+				break;
+			case '\n':
+				s[i++] = '\\';
+				n = 'n';
+				break;
+			case '\r':
+				s[i++] = '\\';
+				n = 'r';
+				break;
+			case '\t':
+				s[i++] = '\\';
+				n = 't';
+				break;
+			case '\v':
+				s[i++] = '\\';
+				n = 'v';
+				break;
+			default:
+				n = t[j];
+				break;
+		}
+		s[i] = n;
+	}
+	s[i] = '\0';
+}

chapter-3-control-flow/4.unescape.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+
+#define MAX_LEN 1024
+
+void unescape(char[], char[]);
+
+main()
+{
+	char t[] = "Hello\\tWorld!!!\\r\\nEOF\\v";
+	printf("%s\n", t);
+	char s[MAX_LEN] = "";
+	unescape(s, t);
+	printf("%s\n", s);
+}
+
+void unescape(char s[], char t[])
+{
+	int i, j, n;
+
+	for (i = 0, j = 0; t[j] != '\0'; i++, j++) {
+		if (t[j] == '\\' && t[j+1] != '\0') {
+			j++;
+
+			switch(t[j]) {
+				case 'a':
+					s[i] = '\a';
+					break;
+				case 'b':
+					s[i] = '\b';
+					break;
+				case 'f':
+					s[i] = '\f';
+					break;
+				case 'n':
+					s[i] = '\n';
+					break;
+				case 'r':
+					s[i] = '\r';
+					break;
+				case 't':
+					s[i] = '\t';
+					break;
+				case 'v':
+					s[i] = '\v';
+					break;
+				default:
+					s[i++] = '\\';
+					s[i] = t[j];
+					break;
+			}
+		} else {
+			s[i] = t[j];
+		}
+	}
+
+	s[i] = '\0';
+}
+