A loop has the form
while <expr> loop <expr> pool
The predicate is evaluated before each iteration of the loop. If the predicate is \(\rm false\), the loop terminates and \(\rm void\) is returned. If the predicate is \(\rm true\), the body of the loop is evaluated and the process repeats.
The predicate must have static type \(\rm Bool\). The body may have any static type. The static type of a loop expression is \(\rm Object\).