Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!kramden.acf.nyu.edu!brnstnd
From: brnstnd@kramden.acf.nyu.edu (Dan Bernstein)
Newsgroups: comp.lang.misc
Subject: Re: Re^2: On whether C has first-class composable functions
Message-ID: <13759:Jan800:19:2391@kramden.acf.nyu.edu>
Date: 8 Jan 91 00:19:23 GMT
References: <442@data.UUCP> <4408:Jan421:44:3391@kramden.acf.nyu.edu> <443@data.UUCP>
Organization: IR
Lines: 39

In article <443@data.UUCP> kend@data.UUCP (Ken Dickey) writes:
>   SCHEME also permits the treatment of functions as full flegded data
>   objects; they may be passed as arguments, returned as values, made
>   part of composite data structures, and notated as independent, unnamed
>   ("anonymous") entities.  {Contrast this with most ALGOL-like
>   languages, in which a function can be written only by declaring it and
>   giving it a name; imagine being able to use an integer value only by
>   giving it a name in a declaration!).

``Full-fledged data objects,'' yes; but ``first-class'' doesn't mean
``full-fledged.''

> More recently, [Kent Dybvig, "The Scheme Programming Language",
> Prentice Hall, 1987]
>   ...procedures are not always named.  Instead, procedures are
>   first-class data objects similar to strings or numbers;  identifiers
>   are bound to procedures in the same way they are bound to other
>   objects. 

Okay, that'd do it; but if that's the definition of ``first-class'' then
you can have first-class objects that you can't pass as function
arguments! I don't think any of us agree with that.

Anyone want to contribute more definitions?

> > > By the way, what function would "apply(compose(compose,f),x);" return in C?
> > > Strike "composable"?
> > What are you talking about? 
  [ explanation ]

Okay, you're saying that you want compose() to apply to the first
argument of a function with many arguments. This would be more useful
if you also had a way to switch around the arguments to a function---
e.g., to convert f(x,y) to g(y,x). There's no reason that these things
can't be done with exactly the same techniques as the one-argument
compose(), so I don't think your example is a reason to say that we're
not talking about composable functions.

---Dan