[GAP Forum] function search feature

[kroeker]

Hello Frank,


thanks, "AllOperations" comes already very close to my needs.
Maybe you could also give me an advice, how to find
all filters which are applicable to an object:

"IsEmpty" is not applicable to an int and therefore
"obj:=5; for each filter in FILTERS do filter(obj); od;"
fails with an error.


Thank you,



Jakob


Am 23.02.2012 23:07, schrieb Frank Lübeck:
> On Thu, Feb 23, 2012 at 08:11:20PM +0000, Alexander Konovalov wrote:
>> I've noticed that this question was not answered yet in the Forum:
>>
>> On 9 Jan 2012, at 09:59, kroeker wrote:
>>
>>> Hello,
>>>
>>> sometimes I am looking for a function which is applicable to a specific object
>>> without knowing the name of the function. To find the desired function
>>> I have to read a lot of documentation, look for examples, ask an experienced GAP programmer (or the GAP-Forum) and so on.
>>>
>>> Would it be possible to implement a search through all existing functions
>>> where one of the parameters is an object of a specified type?
>> So, the short answer is 'No' - GAP function may take any argument(s), one does not
>> specify to which arguments it applies when the function is created. GAP also
>> has a notion of 'operation' which is a bunch of functions, called 'methods'
>> - these are installed with particular requirements on their arguments. Here
>> you may call ApplicableMethod (see ?ApplicableMethod) to get the function
>> which will be applied to arguments in a call to a specified operation - but
>> this is not what you want, since you need to know the name of the operation
>> in advance. For example,
> Dear Jakob, dear Forum,
>
> Sorry, I must have overlooked the original post.
>
> This reminds me that I have once written a utility function
>     AllOperations(obj)
> which returns a list of 6 lists of names of operations such that
> the operations from the i-th list have a method that allows obj as
> argument number i.
>
> I think (a variant of) this is used for a completion function in the
> Sage interface to GAP. The function is appended below.
>
> As Alexander pointed out, something like that is only possible for
> operations (whose methods are installed with requirements on the arguments)
> and not for general functions in GAP.
>
> With best regards,
>    Frank
>