bigdecimal/math.rb: error message in BigMath#PI

* ext/bigdecimal/lib/bigdecimal/math.rb (BigMath#PI): change error
  message about zero or negative precision for clarity and
  consistency with other methods.  [GH-644]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46600 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Author: nobu

ChangeLog

@@ -1,3 +1,9 @@
+Sat Jun 28 20:29:03 2014  Simon Baird  <[email protected]>
+
+	* ext/bigdecimal/lib/bigdecimal/math.rb (BigMath#PI): change error
+	  message about zero or negative precision for clarity and
+	  consistency with other methods.  [GH-644]
+
 Sat Jun 28 15:32:57 2014  Tanaka Akira  <[email protected]>
 
 	* lib/webrick/utils.rb (create_listeners): Close socket objects.

ext/bigdecimal/lib/bigdecimal/math.rb

@@ -180,7 +180,7 @@ def atan(x, prec)
   #   #=> "0.3141592653589793238462643388813853786957412E1"
   #
   def PI(prec)
-    raise ArgumentError, "Zero or negative argument for PI" if prec <= 0
+    raise ArgumentError, "Zero or negative precision for PI" if prec <= 0
     n      = prec + BigDecimal.double_fig
     zero   = BigDecimal("0")
     one    = BigDecimal("1")