[m-rev.] for review: improve documentation for float__pow

[Fergus Henderson]

This is in response to a discussion thread on mercury-users a while back.
It turns out that the final version of LIA-2 says that pow(0.0, 0) = 1.0.
If LIA-2 and R.A.O'K. are in agreement on this issue, that's good enough
for me.

Estimated hours taken: 2

library/float.m:
	Improve the documentation for float__pow.
	In particular, document that pow(0.0, 0) = 1.0.
	This behaviour for pow(float, int) is specified by LIA-2.

Workspace: /home/mercury0/fjh/mercury
Index: library/float.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/float.m,v
retrieving revision 1.34
diff -u -d -r1.34 float.m
--- library/float.m	2001/03/15 07:42:22	1.34
+++ library/float.m	2001/07/04 08:51:02
@@ -136,8 +136,9 @@
 
 	% pow(Base, Exponent) returns Base raised to the power Exponent.
 	% The exponent must be an integer greater or equal to 0.
-	% Currently this function runs at O(n), where n is the value
-	% of the exponent.
+	% pow(0.0, 0) is defined to return 1.0.
+	% In the current implementation, this function takes O(n) time,
+	% where n is the value of the exponent.
 :- func pow(float, int) = float.
 
 	% Compute a non-negative integer hash value for a float.
@@ -258,8 +259,10 @@
 
 	% float__pow(Base, Exponent, Answer) is true iff Answer is
 	% Base raised to the power Exponent.  The exponent must be an 
-	% integer greater or equal to 0.  Currently this function runs
-	% at O(n), where n is the value of the exponent.
+	% integer greater or equal to 0.
+	% pow(0.0, 0) is defined to return 1.0.
+	% In the current implementation, this function takes O(n) time,
+	% where n is the value of the exponent.
 :- pragma obsolete(float__pow/3).
 :- pred float__pow(float, int, float).
 :- mode float__pow(in, in, out) is det.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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