* array.c (rb_ary_choice): a new method to choose an element

  randomly from an array.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@12233 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 20 insertions, 1 deletions

diff --git a/array.c b/array.c
index ac68bd4e0c..7639e22a1a 100644
--- a/array.c
+++ b/array.c
@@ -2899,7 +2899,7 @@ rb_ary_flatten(int argc, VALUE *argv, VALUE ary)
 
 /*
  *  call-seq:
- *     array.shuffle!        -> array or
+ *     array.shuffle!        -> array or nil
  *  
  *  Shuffles elements in _self_ in place.
  */
@@ -2941,6 +2941,24 @@ rb_ary_shuffle(VALUE ary)
 }
 
 
+/*
+ *  call-seq:
+ *     array.choice        -> an_array
+ *  
+ *  Choose a random element from an array.
+ */
+
+
+static VALUE
+rb_ary_choice(VALUE ary)
+{
+    long i = RARRAY_LEN(ary);
+    long j = genrand_real()*i;
+
+    return RARRAY_PTR(ary)[j];
+}
+
+
 /* Arrays are ordered, integer-indexed collections of any object. 
  * Array indexing starts at 0, as in C or Java.  A negative index is 
  * assumed to be relative to the end of the array---that is, an index of -1 
@@ -3037,6 +3055,7 @@ Init_Array(void)
     rb_define_method(rb_cArray, "nitems", rb_ary_nitems, 0);
     rb_define_method(rb_cArray, "shuffle!", rb_ary_shuffle_bang, 0);
     rb_define_method(rb_cArray, "shuffle", rb_ary_shuffle, 0);
+    rb_define_method(rb_cArray, "choice", rb_ary_choice, 0);
 
     id_cmp = rb_intern("<=>");
 }