Finished chapter 2

ch_02/exercise_02-10/main.c

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+/*
+ *
+ * Exercise 2-10. Rewrite the function lower, which converts upper case
+ * letters to lower case, with a conditional expression instead of
+ * if-else.
+ *
+ * Author: Kun Deng
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+
+char lowered[50];
+
+// Makes the string lower case
+char *lower(char *value);
+
+// Returns 1 if value is a valid alphabetic value and 0 if invalid
+int is_valid(char *value);
+
+
+int main(int argc, char **argv)
+{
+    char *x = "soSSDFrSDGFtSGngSGDeSGD\0";
+
+    if (argc == 2)
+    {
+        x = argv[1];
+    }
+
+    int result = is_valid(x);
+
+    if (result == 1)
+    {
+        printf("%s is a valid alphabetic value\n", x);
+        char *lowered = lower(x);
+        printf("%50s %10s %50s\n", "Regular", "|", "Lowered");
+        printf("%50s %10s %50s\n", x, "|", lowered);
+    }
+    else if (result == 0)
+    {
+        printf("%s is not a valid alphabetic value\n", x);
+    }
+
+    return 0;
+}
+
+char *lower(char *value)
+{
+    extern char lowered[];
+    int result = 0;
+    int a;
+
+    for (a = 0; value[a] != '\0'; ++a)
+    {
+        char c = value[a];
+        // printf("%c ", c);
+        lowered[a] = (isupper(c) ? tolower(c) : c);
+    }
+
+    lowered[a] = '\0';
+
+    return lowered;
+}
+
+int is_valid(char *value)
+{
+    int result = 1;
+
+    for (int i = 0; value[i] != '\0'; ++i)
+    {
+        if (!isalpha(value[i]))
+        {
+            result = 0;
+            break;
+        }
+    }
+
+    return result;
+}