Re: [stack] Re: Barebone implementation of concatenative language in c or c++

>
> .
>>>> In a call-by-value environment, It seems to me that encapsulating
>>>> all data in functions yields the same effect as call-by- 
>>>> reference. If
>>>> a parameter is not needed, its evaluating function will not be
>>>> called.
>>>
>>> This gets confusing to me, so hold on tight... :-)
>>>
>>> In order to pass a function to a procedure, the function has to be
>>> available as data. If it's not, you can't pass it.
>>
>> I don't understand this -- I do it all the time in my C code by using
>> the
>> address operator, &, and the same is easily done in Forth, et al.
>
> That's pretty much the same indirection approach I use in Furphy  
> (see http://users.beagle.com.au/peterl/furphy.html), to achieve the  
> same effect with a workaround even when what actually happens is  
> done eagerly. I even describe it there with an analogy to what you  
> are thinking of in C:-
>
> Conditional code is mostly achieved by IF and a complementary pair  
> of things, freezing and thawing. This is a bit like using  
> indirection in C to pass parameters by name instead of the default  
> by value. The analogy here is that IF does eager evaluation, and  
> freezing and thawing change the behaviour to lazy evaluation. IF has  
> this behaviour, using Forth documenting standards: (  true/ 
> false_flag  true_option  false_option  ---  result  ).
>
> FREEZE and THAW behave like an anonymous label (if that isn't a  
> contradiction in terms - it really returns early and pushes a re- 
> entry address to the stack) and a dynamic subroutine call, different  
> from the Forth keyword EXECUTE that it resembles. Typically, you  
> would put FREEZE at the beginning of each keyword that you might  
> want to select with IF and then you would use THAW on whichever one  
> got chosen, like this:-
>
> FREEZE TRUE_STUFF TRUE_OPTION
>
> FREEZE FALSE_STUFF FALSE_OPTION
>
> GET_FLAG TRUE_OPTION FALSE_OPTION IF THAW DEMO
>
> Later on I describe some syntactic sugar to make coding and using  
> the indirection easier, too. P.M.Lawrence.

Thanks. Do you feel your approach is equivalent to lazy evaluation?

don


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