ifelif

Introduction

ifelif allows us to take one action if there are multiple decision points. For example, if you want to take the currency rate of 1 if USD and UKP are not defined, you can write the following program.

Program

Suppose we have three files:

file1.h #define USD 1  file2.h #define UKP 1  file3 #include  #include              //A  #if (defined (USD))                  // B      #define currency_rate 46 #elif (defined (UKP))      #define currency_rate 100       //C #else      # define currency_rate 1        //D #endif  main() {     int rs;     rs = 10 * currency_rate;         //H     printf ("%d\n", rs); } 

Explanation

1. Statement B includes the ifelif directive. It is similar to the else directive.

2. #elif appears only after #if, #ifdef, #ifndef, and #elif.

3. #elif is similar to #else but it is followed by a condition.

4. You can have as many #elif directives as you want.

5. If USD is defined, then the currency rate is 46; otherwise, if UKP is defined, then the currency rate is 100; otherwise, the currency rate is 1.

6. In this case, if you remove the statement include file1.h at position A, then USD and UKP are not defined and currency rate is taken as 1.

Points to Remember

1. #elif is similar to #else but it is followed by a condition.

2. #elif allows taking action in the case of multiple decision points.