25.17.3 try-until ¶

The try-until statement allows you to execute instructions until some exception is caught. The syntax is:

try stmt until exp

where stmt is the statement that will be executed repeatedly until some exception is raised. If the raised exception has type exp then execution continues normally. exp should be an expression that evaluates to an Exception.

This statement is particularly useful for mapping IO spaces until an eof condition occurs. For example, this is how we would compute with every integer in the current IO space:

var o = 0#B;
try
{
  compute (int @ o);
  o = o + 1#B;
} until E_eof;

It is possible to leave the loop from within stmt using the break statement.