Make yourself useful, do-while

Here’s a tedious loop pattern I find myself typing all the time:

    control-code
    while (condition)
      body
      control-code
    endWhile

Two examples:

    cur = cur.next
    while (cur?)
      fn(cur)
      cur = cur.next
    endWhile

    Int32 num = input_Int32( "Enter a positive number: " )
    while (num <= 0)
      println( "Error, number must be positive!" )
      num = input_Int32( "Enter a positive number: " )
    endWhile

In fact, this is what I always attempt to use a repeat-until to solve before realizing it won’t work, like a jigsaw puzzle piece that never quite fits.

Perhaps as a result of my falling-out with repeat-until last night, I was extra sensitive to this issue this morning and resolved to do something about it. Ladies and gentlemen, I present… the reimagined do-while!

    do
      control-code  #scope includes remainder of loop
    while (condition)
      body
    endDoWhile

    do
      cur = cur.next
    while (cur?)
      fn(cur)
    endDoWhile

    do
      Int32 num = input_Int32( "Enter a positive number: " )
    while (num <= 0)
      println( "Error, number must be positive!" )
    endDoWhile

(Edit:)
After realizing that the “while” was ambiguous, I’ve reformulated this structure as a loop-while:

    loop
      cur = cur.next
    continueIf (cur?)
      fn(cur)
    endLoop

It suddenly strikes me that this structure uses a mid-loop termination test, which is kinda neat.