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I just found out about a functional programming language called Joy (see http://www.latrobe.edu.au/philosophy/phimvt/joy.html).
Joy differs from Haskell in that it has no variables. Instead, all functions are postfix, taking a stack as their argument and returning a stack as a result.
Also, IIRC, Joy is untyped. Programming in Joy is like programming with categorical combinators, but ignoring the types. Indeed, a category with one object is just a monoid, and this is supposedly the theory Joy is founded on. But if you really think variables are a nuisance to programming, you can do it in Haskell too, by using list combinators and defining a reverse composition operator. Or just go program in CAML bytecode. It's pretty much the same thing.
Joy advocates contend that the elimination of variables and environments improves on functional languages in much the same way the elimination of state improved on imperative languages.
I think the situations are qualitatively different. Saying that Joy programs "lack variables" is pretty close to saying that its free variable environments are linearly ordered. Yet a Joy programmer can reorder the arguments on the stack if he rewrites his program to take account of that fact. So, though the ordering is really irrelevant, every Joy program must pick one, and that can be understood as non-declarative, since it has nothing to do with the result of the program. FP languages factor out that arbitrary choice by treating free variable environments as (multi-)sets. (Of course, you lose that advantage when you package up your environment in a closure, because Haskell distinguishes between a -> b -> c and b -> a -> c, even though they are isomorphic.) --- Frank Atanassow, Information & Computing Sciences, Utrecht University Padualaan 14, PO Box 80.089, 3508TB Utrecht, The Netherlands Tel +31 (0)30 253-3261 Fax +31 (0)30 251-3791