[Types-sig] types, functional stuff.

[John Skaller]

>Now, John Skaller asked for:
>
>>        compose(f1, f2, f3, f4 ..) # chain in series, 1 arg only
>>        product(f1, f2, f3, f4, ..) # apply componentwise (in parallel)
>>        sum(f1, f2, .. ) # select one of
>>        delta(x,i) = (x,x,x,x,x ..) # i times
>
>so, John: there follow implementations for 3 of these in python

        I already have working implementation in interscript's felix
package.

> The language doesn't need them as built-ins.  

        Yes it does. Your implementation is the same as mine,
and it doesn't work for the same reason: we both use delagation.
This binds the result to the _current_ definition of a function,
not the definition at the point of call.

        For actual functions, this is no problem. They're
immutable. But the compose object is not. It's a class instance
whose definition can be changed by changing the args list.
-------------------------------------------------------
John Skaller    email: skaller@maxtal.com.au
		http://www.maxtal.com.au/~skaller
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