@section gcd: greatest common divisor
@findex gcd
+@c Copyright (C) 2006, 2009-2013 Free Software Foundation, Inc.
+
+@c Permission is granted to copy, distribute and/or modify this document
+@c under the terms of the GNU Free Documentation License, Version 1.3 or
+@c any later version published by the Free Software Foundation; with no
+@c Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+@c Texts. A copy of the license is included in the ``GNU Free
+@c Documentation License'' file as part of this distribution.
+
The @code{gcd} function returns the greatest common divisor of two numbers
@code{a > 0} and @code{b > 0}. It is the caller's responsibility to ensure
that the arguments are non-zero.
If you need the least common multiple of two numbers, it can be computed
like this: @code{lcm(a,b) = (a / gcd(a,b)) * b} or
@code{lcm(a,b) = a * (b / gcd(a,b))}.
-Avoid the formula @code{lcm(a,b) = (a * b) / gcd(a,b)} because - although
-mathematically correct - it can yield a wrong result, due to integer overflow.
+Avoid the formula @code{lcm(a,b) = (a * b) / gcd(a,b)} because---although
+mathematically correct---it can yield a wrong result, due to integer overflow.
In some applications it is useful to have a function taking the gcd of two
signed numbers. In this case, the gcd function result is usually normalized