Date: Fri, 21 Jan 1994 12:06:46 +0100
From: Steve Linton <sal@dcs.st-and.ac.uk>
Message-ID: <8104.9401211106@keith.cs.st-andrews.ac.uk>
To: GAP Forum <GAP-Forum@Math.RWTH-Aachen.DE>
In-Reply-To: <a@b>
Subject: Re: [no subject]

LISP 'apply function:

Since LISP seems to have been an influence in the design of the GAP
language, I wondering whether there might be a (hidden?) function
equivalent to the LISP 'apply function. This function takes as arguments
a function F and a list L and its evaluation is equivalent to a call to F
with arguments given by the elements of L.

i.e. ApplyFunction(F,[a,b,c]) is equivalent to F(a,b,c)

Hear, hear. I have wanted this too and it must be easy to implement.

Nonrecursive PrintRec:

Any chance of including a non-recursive PrintRec in future? When trying
to find out what the fields of a record are there can be an *enormous*
amount of output to wade through (try a GroupHomormorphismByImages
sometime).

Do you know about RecFields?

>
> Matrix calculations:
>
> I need to calculate a number of products of some matrices and add these
> products together. What is the best way of doing this? The simplest
> method, Sum([1..n], i -> A[i]*B[i]), uses much more space than necessary.
> It should be possible to do all this using only two extra matrices, one
> to accumulate the sum, the other to store each product. Can this be done?
>
Trivial with a loop, but Sum ought to get this right as well.

ie Sum(l,f) should be more efficient than Sum(List(l,f))

Steve