====================
For Loops                             !R. Stull, Mar 2007. Univ. Brit. Columbia
====================


! a FORTRAN loop

implicit none                         !enforce strong typing. Recommended.
integer :: i, istart = 3, iend = 10   !declare variables.

do i = istart, iend					  !default increment is assumed to be +1. 
  write(*,*)						  !write a blank line to screen. 
  write(*,*) "INDEX = ",i   		  !display index value on screen.
  
  if (i < 6) cycle                    !optional. skip remaining statements, 
                                      !  but stay inside loop.
  write(*,*) "  line a"
  write(*,*) "  line b"
  
  if (i >= 8) exit                    !optional. skip remaining statements 
                                      !   and leave loop.
  write(*,*) "  line c"
  write(*,*) "  line d"
end do


=====================


/* a C loop */

int i, istart = 3, iend = 10;         /* declare variables. Required in C. */

for (i=istart; i <= iend; i++)
{  
  printf("\n");					      /* write a blank line to screen. */
  printf("INDEX = %d\n",i);           /* display index value on screen. */
  
  if (i < 6) {continue;}              /* optional. skip remaining statements, 
                                          but stay inside loop. */
  printf("  line a\n");
  printf("  line b\n");
  
  if (i >= 8) {break;}                /* optional. skip remaining statements 
                                          and leave loop. */
  printf("  line c\n");
  printf("  line d\n");
}


=====================


# a PERL loop

my $i;                                  # declare variables as local.Recommended
my $istart = 3;
my $iend = 10;

A: for ($i=$istart; $i <= $iend; $i++)  # the label "A" is required only if 
{                                       #   you use "next" or "last" commands.
  print "\n";                           # write a blank line to screen.
  print "INDEX = ",$i,"\n";             # display index value on screen.
  
  next A if $i < 6;                     # optional. skip remaining statements, 
                                        #    but stay inside loop.
  print "  line a\n";
  print "  line b\n";
  
  last A if $i >= 8;                    # optional. skip remaining statements
                                        #    and leave loop.
  print "  line c\n";
  print "  line d\n";

}


====================
OUTPUT IS SAME FROM ALL LANGUAGES
====================

INDEX = 3

INDEX = 4

INDEX = 5

INDEX = 6
  line a
  line b
  line c
  line d

INDEX = 7
  line a
  line b
  line c
  line d

INDEX = 8
  line a
  line b
=======================