Sather - Example of Iterators

Example of Iterators

class MAIN is main is loop i := 1.upto!(10); #OUT + i + "\n"; end; end; end;

This program prints numbers from 1 to 10.

The loop ... end construct is the preferred means of defining loops (although while and repeat-until are also available). Within the construct, one or more iterators may be used. Iterator names always end with an exclamation mark (this convention is enforced by the compiler). upto! is a method of the integer class INT accepting one once argument, meaning its value will not change as the iterator yields. upto! could be implemented in the INT class like this:

upto!(once m:INT):SAME is i: INT := self; -- initialise i to the value of self, -- that is the integer of which this method is called loop if i>m then quit; -- leave the loop when i goes beyond m end; yield i; -- else use i as return value and stay in the loop i := i + 1; -- and increment end; end;

Type information for variables is denoted by a postfix syntax variable:CLASS. The type can often be inferred and thus the typing information is optional, like in anInteger::=1. SAME is a convenience pseudo-class referring to the current class.