Proc#lambda? documented.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@14527 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

proc.c

@@ -107,6 +107,30 @@ proc_clone(VALUE self)
     return procval;
 }
 
+/*
+ * call-seq:
+ *   prc.lambda? => true or false
+ *
+ * Returns true for a Proc object which argument check is rigid.
+ * Such procs are typically generated by lambda.
+ *
+ *   lambda {}.lambda?          => true
+ *
+ *   proc {}.lambda?            => false
+ *   Proc.new {}.lambda?        => false
+ *
+ *   def m() end
+ *   method(:m).to_proc.lambda? => true
+ *
+ *   def n(&b) b.lambda? end
+ *   n {}                       => false
+ *   n(&lambda {})              => true
+ *   n(&method(:m))             => true
+ *   n(&proc {})                => false
+ *   n(&Proc.new {})            => false
+ *
+ */
+
 static VALUE
 proc_lambda_p(VALUE procval)
 {