Looking for a combinator name

Christopher Diggins — 2008-12-06 13:42:00

Hi all,



I am looking for a name for a combinator that is equivalent to:



In Cat: dip apply

Or in Joy: dip i



This turns out to be a very useful combinator when doing code

compression. Given two functions:



define f { a0 .. aN x b0 .. bN }

define g { a0 .. aN y b0 .. bN }



We can reduce the size by rewriting it as:



define h { [a0 .. aN] dip apply b0 .. bN }

define f { [x] h }

define g { [y] h }



Any suggestions would be appreciated.



- Christopher

John Nowak — 2008-12-07 13:08:04

On Dec 6, 2008, at 8:42 AM, Christopher Diggins wrote:



 > I am looking for a name for a combinator that is equivalent to:

>

> In Cat: dip apply

> Or in Joy: dip i



 
I can't say that I understand what you'd use this for and hence I'm  

having trouble coming up with a name. I've often used 'dup dip i' (aka  

'twice'), but never just 'dip i'. Do you have a more concrete example?



- John

Christopher Diggins — 2008-12-07 17:28:45

On Sun, Dec 7, 2008 at 8:08 AM, John Nowak <john@...> wrote:

 > On Dec 6, 2008, at 8:42 AM, Christopher Diggins wrote:

>

>> I am looking for a name for a combinator that is equivalent to:

>>

>> In Cat: dip apply

>> Or in Joy: dip i

>

> I can't say that I understand what you'd use this for and hence I'm

> having trouble coming up with a name. I've often used 'dup dip i' (aka

> 'twice'), but never just 'dip i'. Do you have a more concrete example?



 
No I don't. I have only seen it when refactoring concatenative code.



Lets call it q for a second:



... [a] [b] q => ... b a



I believe the following is the applicative form:



\abc.b(a(c))



Another way of writing it is:



q = swap compose apply



or in Joy:



q = swap cat i



- Christopher

Christopher Diggins — 2008-12-07 17:30:37

Just found a name at : http://tunes.org/~iepos/joy.html



Brent calls it "sap".



- Christopher



 On Sun, Dec 7, 2008 at 12:28 PM, Christopher Diggins <cdiggins@...> wrote:

> On Sun, Dec 7, 2008 at 8:08 AM, John Nowak <john@...> wrote:

>> On Dec 6, 2008, at 8:42 AM, Christopher Diggins wrote:

>>

>>> I am looking for a name for a combinator that is equivalent to:

>>>

>>> In Cat: dip apply

>>> Or in Joy: dip i

>>

>> I can't say that I understand what you'd use this for and hence I'm

>> having trouble coming up with a name. I've often used 'dup dip i' (aka

>> 'twice'), but never just 'dip i'. Do you have a more concrete example?

>

> No I don't. I have only seen it when refactoring concatenative code.

>

> Lets call it q for a second:

>

> ... [a] [b] q => ... b a

>

> I believe the following is the applicative form:

>

> \abc.b(a(c))

>

> Another way of writing it is:

>

> q = swap compose apply

>

> or in Joy:

>

> q = swap cat i

>

> - Christopher

>