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

I think I should mention CityScript (the scripting language of CityDesk) which has some really fancy looping constructs.

From the help file:

{$ forEach n var in (condition) sort-order $}
... text which appears for each item ....
{$ between $}
.. text which appears between each two items ....
{$ odd $}
.. text which appears for every other item, including the first ....
{$ even $}
.. text which appears for every other item, starting with the second ....
{$ else $}
.. text which appears if there are no items matching condition ....
{$ before $}
..text which appears before the loop, only if there are items matching condition
{$ after $}
..text which appears after the loop, only of there are items matching condition
{$ next $}

Answer 2

foo();

while(condition)
{
   bar();
   foo();
}

Answer 3

Loop with else:

while (condition) {
  // ...
}
else {
  // the else runs if the loop didn't run
}

Answer 4

Also note that many control structures get a new meaning in monadic context, depending on the particular monad - look at mapM, filterM, whileM, sequence etc. in Haskell.

Answer 5

if not:

unless (condition) {
  // ...
}

while not:

until (condition) {
  // ...
}

Answer 6

Something that replaces

bool found = false;
for (int i = 0; i < N; i++) {
  if (hasProperty(A[i])) {
    found = true;
    DoSomething(A[i]);
    break;
  }
}
if (!found) {
  ...
}

like

for (int i = 0; i < N; i++) {
  if (hasProperty(A[i])) {
    DoSomething(A[i]);
    break;
  }
} ifnotinterrupted {
  ...
}

I always feel that there must be a better way than introducing a flag just to execute something after the last (regular) execution of the loop body. One could check !(i < N), but i is out of scope after the loop.