Sather

Sather is an

Originally, it was based on Eiffel, but it has diverged, and now includes several functional programming features.

The name is inspired by Eiffel; the

 class HELLO_WORLD is
  main is 
   #OUT+"Hello World\n"; 
  end; 
 end;

• Class names are ALL CAPS; this is not only a convention but it's enforced by the compiler.
• The method called main is the entry point for execution. It may belong to any class, but if this is different from MAIN, it must be specified as a compiler option.
• # is the constructor symbol: It calls the create method of the class whose name follows the operator. In this example, it's used for instantiating the OUT class, which is the class for the standard output.
• The + operator has been overloaded by the class to append the string passed as argument to the stream.
• Operators such as + are syntactic sugar for conventionally named method calls: a + b stands for a.plus(b). The usual arithmetic precedence conventions are used to resolve the calling order of methods in complex formulae.

Example of iterators

This program prints numbers from 1 to 10.

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

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 INT class accepting one once argument, meaning its value won't change as the iterator yields. upto! could be implemented in the INT class with code similar to the following one.

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

References

External links

• Sather homepage