Dropped: Do-While

The syntax construct

do <body> while <cond>

is no longer supported. Instead, it is recommended to use the equivalent while loop below:

while ({ <body> ; <cond> }) ()

For instance, instead of

do
   i += 1
while (f(i) == 0)

one writes

while
   i += 1
   f(i) == 0
do ()

The idea to use a block as the condition of a while also gives a solution to the "loop-and-a-half" problem. Here is another example:

while
   val x: Int = iterator.next
   x >= 0
do print(".")

Why Drop The Construct?

  • do-while is used relatively rarely and it can expressed faithfully using just while. So there seems to be little point in having it as a separate syntax construct.
  • Under the new syntax rules do is used as a statement continuation, which would clash with its meaning as a statement introduction.