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MAKUNBOUND vs. special binding
- To: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
- Subject: MAKUNBOUND vs. special binding
- From: David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>
- Date: Fri, 30 Jan 87 16:00 EST
- Cc: Common-Lisp@SAIL.STANFORD.EDU, Pavel.pa@XEROX.COM
- In-reply-to: <146816.870130.JAR@AI.AI.MIT.EDU>
- Line-fold: No
Date: Fri, 30 Jan 87 12:21:21 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
(1) A variable is bound to
a value when evaluating that variable produces that value, and is
unbound when evaluating that variable is an error. (2) A special
variable is bound when its value has been saved upon entry to a
dynamic extent, and will be restored upon exit.
Just for the record, MIT Scheme solves this terminology problem by using
the terms "bound" and "unassigned". "Unbound" refers more or less to
(2) and "unassigned" to (1).
This sounds quite good to me. The only problem for Common Lisp is that all
uses of "bind" (actually "bound") in function names (as opposed to text of
the manual) are meaning (1). We just can't win.