Two beginner questions

[Peter Van Roy]

The problem is the '<=' in N<=D.
The less-than-or-equal is written '=<' in Oz
(see the table on page 55 of the Oz book
or the index on page 863).  You have to
write (N=<D) and then everything works!

The '<=' is an arrow symbol that is reserved
for optional arguments in method definitions.

Peter


Urban Hafner wrote:

> Torsten Anders wrote:
>
> | The error message says it all:
>
> Yes. I seems I had forgotten the then. But when I add the then I somehow
> doesn't change that much. I also added parens around the predicate which
> then results in another error message. Here's the code:
>
> declare Accum in
> local C in
> ~   C={NewCell 0}
> ~   fun {Accum N}
> ~      D=@C
> ~   in
> ~      if (N<=D) then
>      C:=D+N
> ~      else
>      C:=D-N
> ~      end
> ~      @C
> ~   end
> end
>
> And this is the error message:
>
> %*************************** parse error ************************
> %**
> %** expecting `)'
> %**
> %** in file "/Users/urban/blog/book/CTMCP/parse-error.oz", line 7, 
> column 11
> %** ------------------ rejected (1 error)
>
> The compiler strangely thinks that right after the N a closing paren.
>