Useful alternative control structures?

Question

Sometimes when I am programming, I find that some particular control structure would be very useful to me, but is not directly available in my programming language. I think my

Answer 1

One of the control structures that isn't available in many languages is the case-in type structure. Similar to a switch type structure, it allows you to have a neatly formatted list of possible options, but matches the first one that's true (rather then the first one that matches the input). A LISP of such such (which does have it):

(cond
   ((evenp a) a)        ;if a is even return a
   ((> a 7) (/ a 2))    ;else if a is bigger than 7 return a/2
   ((< a 5) (- a 1))    ;else if a is smaller than 5 return a-1
   (t 17))              ;else return 17

Or, for those that would prefer a more C-like format

cond 
    (a % 2 == 0): 
        a;     break;
    (a > 7):
        a / 2; break;
    (a < 5):
        a - 1; break;
    default:
        17;    break;

It's basically a more accurate representation of the if/elseif/elseif/else construct than a switch is, and it can come in extremely handing in expressing that logic in a clean, readable way.