Re: lazy evaluation: Goops class/instance customization

[Mikael Djurfeldt]

Maarten Grachten <address@hidden> writes:

> On Wed, 21 May 2003, Mikael Djurfeldt wrote:
>
>> Why are you using `primitive-eval'?
>> 
>> Shouldn't it be simply "(if (promise? v) (force v) v)"?
>
> Well, without the eval the getter gives me back just the variable, and I 
> want the value of the variable (if there is one, and an unbound variable 
> error otherwise).

Then, in order to get correct semantics, you should remove
`primitive-eval' and instead use the following (untested) version of
make-lazy:

(defmacro make-lazy (specification . body)
  (let ((attributes (map (lambda (x)      
                           (if (keyword? x)
                               x
                               `(delay ,x)))
                         body)))
                `(make ,specification
                       ,@attributes)))