Re: What is the "+/" operator?

On 05/23/2007 06:50 PM, Bill Page wrote:
> Quoting Martin Rubey <[email protected]>:
> 
>> ... Igor Khavkine writes:
>>
>>> Can someone explain this syntax? Looking at the Axiom .spad files,
>>> I see that it has general usage +/[...some list construction...]. 
>>
>> It is old syntax for reduce and should go away.

I very much agree. The reason is that one should give an initial value 
otherwise you might be surprised.

woodpecker:~/scratch>aldor -fx -laldor aaa.as
woodpecker:~/scratch>aaa
Sum:  29
Prod: 0

But if you like the

f/[a,b,c]

syntax, you can actually define a similar things in Aldor. (I guess, 
SPAD would be just the same.)

Ralf

---BEGIN aaa.as
#include "aldor"
#include "aldorio"

macro Z == Integer;

Pkg: with {
	/: ((Z, Z) -> Z, List Z) -> Z;
} == add {
	(f: (Z, Z) -> Z) / (l: List Z): Z == {
		empty? l => 0;
		f(first l, f/(rest l));
	}
}

main(): () == {
	import from Pkg;
	l1: List Z := [2,4,6,8,3,5,1];
	sum: Z  := (+)/l1;
	prod: Z := (*)/l1;
	stdout << "Sum:  " << sum << newline;
	stdout << "Prod: " << prod << newline;
}

main();
---END aaa.as