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What do the bindings bind then? So, no, even in pure functions like f x = x + 1 x is a bound variable. It doesn't 'vary' in the sense that the value it r

• TylerE 13y ago
  It is rebound. It is improper to call it a "variable" because in any given lifetime, it's value cannot vary. That's the point. It is possible to create a new binding with the same name, but any code holding on to the old instance keeps the old value. Subtle but important difference.
  • mbrock 13y ago
    You're simply wrong. That's not how the term "variable" works. From http://en.wikipedia.org/wiki/Variable_(mathematics) http://en.wikipedia.org/wiki/Variable_(mathematics): "Varying, in the context of mathematical variables, does not mean change in the course of time, but rather dependence on the context in which the variable is used."
    • tel 13y ago
      While I agree with your philosophy of vocabulary here, I've read the Harper article too, it's valuable to state directly that everyone knows there's the _(Programming) article too and is simply disagreeing that its a "good" way to use the term. Anyone who isn't familiar with the distinction in terminology ought to consider what things a programming variable represents that a mathematics variable does not..
    • Symmetry 13y ago
      From http://en.wikipedia.org/wiki/Variable_%28programming%29 http://en.wikipedia.org/wiki/Variable_%28programming%29 "The identifier in computer source code can be bound to a value during run time, and the value of the variable may thus change during the course of program execution. Variables in programming may not directly correspond to the concept of variables in mathematics."
      • mbrock 13y ago
        It's wrong that it's "improper" to use the term "variable" for Haskell variables, since it is an established usage. This usage of "variable" occurs in the very first paragraph of Church's first paper on lambda calculus from 1931 in the motivation for the whole project!
    • iopq 13y ago
      Math doesn't have vars, only vals
      • mbrock 13y ago
        That's a rather strange assertion, if you mean "variables" and "values." Math distinguishes between variables and values. Variables have different values. Values can be bound to variables. Sometimes we do math with mostly variables and few values -- that's called algebra.
        • iopq 13y ago
          I mean Scala vars can be changed during the program, while Scala vals can't. val y = Console.readInt var x = y + 1 x = y + 2 //valid y = 5 //error, vals can't be changed in the same block