[Scilab-users] Anonymous functions

[Pierre Vuillemin]

Hi Samuel,

Indeed, the behaviour I seek to reproduce is similar to what could be 
done with a global variable. Yet I would avoid to resort to global 
variables.

 From what I've understand about variables scoping in Scilab 
(https://wiki.scilab.org/howto/global%20and%20local%20variables), 
variables from the above level are only replaced/copied locally when 
needed, e.g.

function outer()
   a = 1
     function inner()
       disp(a) // a has the value of the outer function
       a = 2   // now a copy is made and a is locally equal to 2
     endfunction
   inner()
   disp(a) // a has kept its initial value of 1
endfunction


Hence I guess that the fact that a = 1 in the scope of the outer 
function is stored somewhere so that Scilab can retrieve that 
information when needed. I'm wondering how it works internally and 
whether I could use this to create generic lambda function?

I'm aware that this cannot be done solely in Scilab but requires to 
fiddle with the C interface, but I'm curious to experiment.


Regards,

Pierre


Le 17.01.2017 14:21, Samuel Gougeon a écrit :
> Le 17/01/2017 11:46, Pierre Vuillemin a écrit :
>> I have actually implemented a similar solution (in the previous link) 
>> except that the data are stored in some list. This leads to anonymous 
>> functions that behaves as in Matlab, i.e. the data of the function is 
>> instantiated when the function is created.
>> 
>> In python, the value of the data 'a' is instantiated when the function 
>> is evaluated. Therefore, if the data 'a' changes, the function 
>> changes.
>> 
>> Here I could make something like
>> 
>> deff('y=f(x)','y = a*x')
>> 
>> but then the function will get the value of the variable 'a' of the 
>> current namespace, e.g.
>> 
>> a = 1
>> function outer(x)
>>  a = 2
>>  disp(f(1))
>> endfunction
>> 
>> f(1)     // will give 1
>> outer(1) // will give 2
>> a = 3
>> f(1)     // will give 3
>> outer(1) // will give 2
>> 
>> In this example, I would like f(1) to behave identically independently 
>> of its position.
> 
> If i understand correctly your query, the global space is unique and
> aims to allow that:
> deff('y=f(x)','global a; y = a*x')
> 
> This requires the only variable "a" you want to consider been declared
> "global a" before some calling point. Actually, i don't see how to
> refer to a unique "a" without telling to Scilab which one it must be.
> 
> Samuel
> 
> 
> 
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