the problem of using _Var instead of _

Richard A. O'Keefe <>
Sun Mar 6 22:57:56 CET 2005


Bengt Kleberg <> wrote:
	i have operated under the assumption that _ and _<Var> are the 
	same for over four years now.
	
The language description made it quite clear that this is not so.
In ML, CAML, Haskell, Clean, Prolog, Mercury, and Erlang, in fact
in _all_ the programming languages I've used which have pattern
matching standardly built into their procedure-calling machinery,
"anonymous variable" syntax gives you a new distinct variable
each time you use it, while this is not true for any other kind of
variable, no matter how spelled.

Variable name		New each	Warn if		Warn if
matches regexp		time?		=1 occ?		>1 occ?

/_/			yes		no		no
/_[a-zA-Z0-9_]+/	no		no		no[%]
/[A-Z][a-zA-Z0-9_]*/	no		yes		no

[%] It looks as though there _should_ be a warning.



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