macro implementations

macros.c

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+/**
+ * @file macros.c
+ * @author kunal jain ([email protected])
+ * @brief Program to demonstrate macros
+ * @version 0.1
+ * @date 2022-02-21
+ * 
+ * @copyright Copyright (c) 2022
+ * 
+ */
+
+#include<stdio.h>
+
+#define STATE 1
+
+// Macros may not work as expected when
+// defined without brackets.
+#define SQUARENB(A) (A*A)      // Macro without brackets around expression
+#define SQUARE(A) ((A)*(A))    // Macro with brackets around expression 
+
+// Use backslash (\) to write macro definition in two line.
+// Following macro swaps value of x and y. t is data type int.
+#define EXCHG(t, x, y) { t d; d = x; x = y;\
+         y = d;}
+
+
+// This function shows how to
+// use macros without arguments.
+void test_macro_no_arg() {
+    if (STATE) {
+        printf("Macro substitution works!");
+    }
+}
+
+// This function shows how to 
+// using macro with arguments.
+void test_macro_arg() {
+    int n = 9;
+    n = SQUARENB(n + 1);    // Substitution -> (n + 1*n + 1)
+    printf("Value of n when no brackets in Macro definition -> %d\n", n);
+    n = 9;
+    n = SQUARE(n + 1);      // Substitution -> ((n + 1)*(n + 1))
+    printf("Value of n brackets in Macro definition -> %d\n", n);
+}
+
+// Using EXCHG macro to swap
+// values of two variables.
+void test_macro_exchg() {
+    int a = 5, b = 7;
+    printf("Value of a and be is %d and %d respectively\n", a, b);
+    EXCHG(int, a, b);
+    // Above macro expands as follows
+    // Shown in multiple lines for clarity
+    // {
+    //     int d;
+    //     d = u;
+    //     u = v;
+    //     v = d;    
+    // }
+    // In above expansion, d is defined locally within block.
+    printf("Value of a and be is %d and %d respectively\n", a, b);
+}
+
+// An example of conditional macros
+void test_conditional_inclusion() {
+
+    // Evaluates to true if STATE macro is defined
+    #ifdef STATE
+        printf("State macro is defined\n");
+
+    // This runs if above condition false
+    #else
+        printf("State macro is not defined\n");
+
+    // Always remember to end conditional macros
+    #endif
+}
+
+int main(void) {
+
+    // This is driver function. We call all function
+    // from this driver function.
+
+    // Uncomment the function that you want to run
+    // and check the output for.
+
+    // test_macro_no_arg();
+    // test_macro_arg(); 
+    // test_macro_exchg();
+    // test_conditional_inclusion();
+
+    return 0;
+}