Initial commit

Completed exercise

Author: fsaadatmand

chapter07/7-9.c

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+/*
+ * Exercise 7-9. Functions like isupper can be implemented to save space or to
+ * save time. Explore both possibilities.
+ *
+ * Answer: I take it that by saving space the authors mean increasing code
+ * compactness and by saving time reducing run time.  Implementing isupper() as
+ * a macro avoids the overhead associated with calling a function on to the
+ * stack memory; thus, we save time. I suppose it could be argued that this
+ * saves stack memory as well, but I do not think that is what the authors
+ * meant.  To save space, we could implement a macro such as IFUPPER that wraps
+ * an "if ..."  statement around the isupper() function. The result is a
+ * one-line code that performs multiple instructions. Moreover, if we avoid
+ * using other functions in the wrapping and use nested macros instead, we
+ * could save both time and space. The draw back, of course, is that the code,
+ * though more readable, it will be full of unconventional idioms.
+ *
+ * By Faisal Saadatmand
+ */
+
+#include <stdio.h>
+#include <ctype.h>
+
+#define ISUPPER(c) ((c) >= 'A' && (c) <= 'Z') ? 1 : 0            /* saves time */
+#define TOLOWER(c) ((c)) + 'a' - 'A'                             /* saves time */
+#define IFUPPER_TOLOWER(c) if (isupper((c))) (c) = tolower((c))  /* saves space */
+#define IF_UPPER_TOLOWER(c) if (ISUPPER((c))) (c) = TOLOWER((c)) /* saves time and space */
+#define IF_UPPER(c,a) (ISUPPER((c))) ? ((a)) : ((c))             /* saves time and space */
+
+int main(void)
+{
+	int c;
+
+	printf("Enter an upper case character: " );
+	c = getchar();
+
+	if (ISUPPER(c))
+		c = tolower(c);
+	printf("%c\n", c);
+
+	IFUPPER_TOLOWER(c);
+	printf("%c\n", c);
+
+	IF_UPPER_TOLOWER(c);
+	printf("%c\n", c);
+
+	printf("%c", IF_UPPER(c, TOLOWER(c)));
+	printf("\n");
+
+	return 0;
+}