Fortran - if-else if-else Construct | Adglob Infosystem Pvt Ltd

In this guide, we will discuss Fortran if-else if-else construct. An if statement construct can have one or more optional else-if constructs. When the if condition fails, the immediately followed else-if is executed. When the else-if also fails, its successor else-if statement (if any) is executed, and so on.

The optional else is placed at the end and it is executed when none of the above conditions hold true.

All else statements (else-if and else) are optional.
else-if can be used one or more times.
else must always be placed at the end of construct and should appear only once.

Syntax

The syntax of an if…else if…else statement is −

[name:] 
if (logical expression 1) then 
   ! block 1   
else if (logical expression 2) then       
   ! block 2   
else if (logical expression 3) then       
   ! block 3  
else       
   ! block 4   
end if [name]

Example

program ifElseIfElseProg
implicit none

   ! local variable declaration
   integer :: a = 100
 
   ! check the logical condition using if statement
   if( a == 10 ) then
  
      ! if condition is true then print the following 
      print*, "Value of a is 10" 
   
   else if( a == 20 ) then
  
      ! if else if condition is true 
      print*, "Value of a is 20" 
  
   else if( a == 30 ) then
   
      ! if else if condition is true  
      print*, "Value of a is 30" 
  
   else
   
      ! if none of the conditions is true 
      print*, "None of the values is matching" 
      
   end if
   
   print*, "exact value of a is ", a
 
end program ifElseIfElseProg

When the above code is compiled and executed, it produces the following result −

None of the values is matching
exact value of a is 100

Next Topic : Click Here