Higher order functions and templates

[Mike Jones]

The introduction has this statement:

In ATS2, linear closure-functions become much less important as programming with higher-order functions in a setting without GC can be more conveniently achieved through the use of templates.

I'm struggling to know why this conclusion. A higher order function takes a function as an argument, which is just a closure, or closure with no values in an environment. I can see that templates add flexibility in the signature of the closure as the template can take compatible parameters and be more generic, such as a generic map function.

But I don't understand how this makes closures less important.

[gmhwxi]

Maybe the last example on the homepage of ats-lang could shed some light:

http://www.ats-lang.org/

[Mike Jones]

Does the implement in a where clause only work for templates?

[Mike Jones]

And I assume the implement can't capture values like a closure because it has to compile everything up front. Correct?

[Hongwei Xi]

You are right. It cannot.

On Sun, Jan 3, 2016 at 9:12 PM, Mike Jones <proc...@gmail.com> wrote:

And I assume the implement can't capture values like a closure because it has to compile everything up front. Correct?

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[Mike Jones]

And the implements functions must be templates? I'll guess yes, because template is a natural thing to expand.
Can the function around the implementations be a non template? I'll guess no, because the inner expansion probably relies on an outer expansion.

Where expand means instance.

[gmhwxi]

>>Can the function around the implementations be a non template?

Yes, it can be a non-template function.

It is very often that you want to implement a template inside a
non-template function. In this way, the template function gets to
access to the arguments of the non-template function.

Please take a look at wordcnt2.dats at the word-counting example:

http://ats-lang.sourceforge.net/EXAMPLE/EFFECTIVATS/

Using templates properly can greatly reduce complexity in programming.

Say someone is asked to implement the following example involving some drawing:

http://ats-lang.sourceforge.net/EXAMPLE/EFFECTIVATS/Sierpinski-3angle/Sierpinski-3angle.html

Most likely, the person would immediately think about the canvas. In my opinion, the person should
focus on drawing and forget about the canvas for a while. This is very easy to achieve with templates.

Having too much stuff on one's mind clutters the mind.