Simulating the "continue" directive, and other alternatives

Question

Some programming languages support a "continue" directive in loops to skip to the next loop. How do you achieve the same thing in languages that don't have this directive? I am facing a situation now in povray where I need this behavior. Thanks.

Answer 1

In the simplest case, just use a conditional:

#for (i, from, to)
  // do common actions
  #if (<condition is true>)
    // do something special to the condition
  #end
#end

Alternatively, POV-Ray 3.7 supports the #break statement that you can use to emulate continue with a little help from recursion - however, this is quite clumsy and inelegant:

#macro LoopWithContinuation(from, to)
  #for (i, from, to)
    #if (<condition is true>)
      LoopWithContinuation(i + 1, to)
      #break
    #else
      // do something
    #end
    #debug ""
  #end
#end

LoopWithContinuation(1, 20)

Keep in mind, though, that POV-Ray has a fixed recursion depth limit of 200, so this approach is not suitable for longer loops.