[plt-scheme] signed unit syntax

Ahem!

Actually the code below doesn't work - still had my previously evaluated 
working version invoked with define-value/invoke-unit/sig available in 
the REPL that was being called:

;  (define compound@
;     (compound-unit/sig
;         (import)
;         (link
;          (COMP : c^ (sqrt-sum-squares@))
;          (OUT : o^ (simple-output@)))
;         (export (open COMP) (open OUT))))
; 
; 
;  (define-signature compound^ ((open c^) (open o^)))
; 
; 
;  (define-values/invoke-unit/sig compound^ compound@)

Give me another few minutes to get it right, or hopefully a units expert 
will answer...

Apologies PLT-ers.

Stephen

Stephen Tetley wrote:

>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>
> Hello David
>
> I believe you just need the expression inside the old friend the begin 
> form then the compound-unit gets invoked before its called:
>
> (define output-sqrt-sum-squares
>    (lambda (x y)
>      (begin
>        (invoke-unit/sig
>         (compound-unit/sig
>           (import)
>           (link
>            (COMP : c^ (sqrt-sum-squares@))
>            (OUT : o^ (simple-output@)))
>           (export (open COMP) (open OUT))))
>        (output (computation x y)))))
>
> Presume you mean to call computation rather than distance as well :-) 
> Then at the prompt you can call the function:
>
> > (output-sqrt-sum-squares 3 4)
> value = 25
> >
>
>
> Best wishes
>
> Stephen Tetley
>
> David J. Neu wrote:
>
>>  For list-related administrative tasks:
>>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>>
>> Hi all,
>>
>> I'm trying to get a handle around some of the syntax for signed units
>> and have attached a simple toy example to show where I'm stuck.
>>
>> In the example, there are two units one that performs some simple
>> computation and one that displays formatted output.  I have a function
>> called _output-sqrt-sum-squares_ which consumes the values to submit
>> to the computation and tries to run the compuation and output the
>> result.
>>
>> The error I'm getting is
>>  
>>
>>> reference to undefined identifier: output
>>>   
>>
>> Clearly a lack of understanding on my part.
>>
>> Thanks in advance for any help!
>>
>> Cheers,
>> David
>>
>>
>> (require (lib "unitsig.ss"))
>>
>> (define-signature c^ (computation))
>>
>> (define-signature o^ (output))
>>
>> (define sqrt-sum-squares@
>>  (unit/sig c^
>>       (import)
>>       (define square
>>      (lambda (x) (* x x)))
>>       (define computation
>>      (lambda (x y)
>>        (+ (square x) (square y))))))
>>
>> (define simple-output@
>>  (unit/sig o^
>>       (import)
>>       (define output
>>      (lambda (v)
>>        (printf "value = ~a~n" v)))))
>>
>> (define output-sqrt-sum-squares
>>  (lambda (x y)
>>    (invoke-unit/sig
>>     (compound-unit/sig
>>       (import)
>>       (link
>>        (COMP : c^ (sqrt-sum-squares@))
>>        (OUT : o^ (simple-output@)))
>>       (export (open COMP) (open OUT))))
>>    (output (distance x y)))) ; *** I don't know how to make this 
>> procedure call ***
>>
>> (output-sqrt-sum-squares 2 4)
>>
>>
>>
>>  
>>
>
>
>