Yes, the delay and force does the job. Now it would be nice to hide delay
declaration in arguments destruction as already proposed:
(den mycrazyif [ statement ~onsuccess ~onfailure ] ; nonsuccess and on
failure becomes delay objects
(if statement ; just evalutated with mycrazyif call
@onsucess ; deref block in case of success
@onfailure)) ; deref block in case of failure
On Tuesday, 26 April 2016 19:59:12 UTC+2, Michael Griffiths wrote:
>
> I'm not sure I fully understand your proposal, but when I really need lazy
> evaluation (which is pretty rare) I reach for `delay` and `force`.
>
> On Tuesday, 26 April 2016 16:41:08 UTC+1, Olek wrote:
>>
>> Hi!
>>
>> In short:
>>
>> I have noticed that in most cases I use macros only for lazy arguments
>> evaluation. Why not to make something to use only this feature? It would be
>> light version of macro for clojurescript/clojure and easy to grasp for
>> newcomers and still powerful in programming (with that you could implement
>> binding/scopes/interpreter pattern). I love implicite use of macros where
>> from call point of view the user can't distinguish what is function and
>> what is macro.
>>
>> In long:
>>
>> Generally the macros are used in compile phase to manipulate AST (or just
>> data structures because Clojure is homoiconic) to produce code in order to
>> be consumed in evaluation phase.
>> It is nice to include new language constructs with use of macros but as
>> my experience points out for most time I use macros only for changing
>> evaluation moment/order.
>> Maybe there should be some construct like "defnlazy" for which you write
>> normal function but all input arguments are evaluated only when you
>> explicitly evaluate them.
>> What we gain? We don't have to deal with # ` @ list eval and separate
>> thoughts on read/eval phases, but we still must explicitly say ~ to deref
>> passed block of construct as argument.
>>
>> Also there are some problems to grasp:
>> - is it safe to implicite convert blocks of construct from statements to
>> deref objects
>> - how it should behave when you pass not deref object to another
>> discussed "defnlazy"
>> - maybe there shouldn't be any defnlazy but you should just implement it
>> in arguments destruction so you can use constructs like:
>>
>> (defn mycrazyif [ statement ~onsuccess ~onfailure ]
>> (if statement ; just evalutated with mycrazyif call
>> @onsucess ; deref block in case of success
>> @onfailure)) ; deref block in case of failure
>>
>>
>> With regards,
>> Olek
>>
>
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