What is a good alternative to the name variable for a language that only has immutable references or labels?

Question

For example, in functional languages, variables are single assignment and their values are immutable once assigned. So they have two states unbound and bound, once bound they can't be changed.

Is there some mathematical term or other computer science term that is most appropriate for such as thing? Something that semantically doesn't imply variance or mutability.

If not there doesn't exist such as term and if you were designing a language that had such constructs, what other than the word variable would you use to for these?

I am not really looking to poll for ideas, I am trying to figure out if there is already an accepted industry ( any industry ) term for such a thing.

Answer 1

What about "symbol"?

I saw a video on F# where the speaker said,

you do not assign a value to a variable, you bind a value to a symbol.

(Still looking for the reference for this.)

Whenever I encounter the word "variable" in places where such constructs are immutable, I silently think "bound symbol."

Answer 2

Just call them variables. Math has variables; functional languages have the same kind of variables.

See also this essay by Bob Harper on this terminology issue.

Answer 3

It's still a variable if it can take on various values in different invocations. In other words, even though it can't be changed once assigned, that symbol can be assigned to different values initially. That's in contrast to a constant which contains the same value every time it is invoked.

Answer 4

constant, or const would probably be familiar to people using languages such as C and C++,

Answer 5

Why not just stick with that term? It may not be 100% appropriate, but when you choose a different name that will probably a cause of more misunderstandings than the ones you try to solve. Designers of other functional languages may had the same problem, but they decided to use the term "variable", either.

XSLT (which is widely used):

http://www.w3schools.com/xsl/el_variable.asp

Haskell:

http://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-240003.2

Scheme:

http://www.scheme.com/tspl2d/binding.html

Erlang:

http://www.erlang.org/doc/reference_manual/expressions.html

All of them are using the term "variable", too.

Of course, other language designers prefer to talk of "bindings" or "bound values", like here for F#:

http://msdn.microsoft.com/en-us/library/dd233238.aspx

Answer 6

Depending on the contex "variable" or "binding" would work. I think "binding" is more likely to come up in statements like let in Haskell or Lisp.

Answer 7

Name. The same thing may be reasonably called by multiple names (x = 4; y = 4); and a name, once defined, never changes its referent. x = 2; x = 3 makes just as little sense as saying that an octopus is not an octopus.