SELECT CASE

Syntax:

$[\langle name \rangle :]$	SELECT CASE ( )
	CASE ( )
	CASE DEFAULT
	END SELECT

• must be a scalar of type INTEGER, LOGICAL or CHARACTER;
• can be a single value (.TRUE.) or a range (); one cannot use an expression as case selector.
• is evaluated and compared to the s, in order; when a match is found, the branch is taken and the corresponding executed. If no matches then the CASE DEFAULT branch is executed, if present.
• At the end of in the selected branch the control is passed to the first statement following END SELECT.

A CASE SELECT function can be implemented with an IF ... ELSEIF... ENDIF construction; however, the former needs a different expression to evaluate at each branch, and is therefore less efficient. Example:

select case (i)
  case (:0)   ; print*, "i<=0"
  case (1)    ; print*, "i=1"
  case default; print*, "i>=2"
end select

program season
  implicit none
  integer::month
  print*,'Give month'
  read*,month
  select case (month)
  case (12,1,2)
    print*,'Month ',month,' is in winter'
  case(3:5)   !this is range from 3 to 5
    print*,'Month ',month,' is in spring'
  case(6:8)
    print*,'Month ',month,' is in summer'
  case(9:11)
    print*,'Month ',month,' is in fall'
  case default
    print*,'invalid month: ',month
  end select
end program season