diff options
| -rw-r--r-- | mrbgems/mruby-random/src/random.c | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/mrbgems/mruby-random/src/random.c b/mrbgems/mruby-random/src/random.c index 4ef009c54..fb2b531b5 100644 --- a/mrbgems/mruby-random/src/random.c +++ b/mrbgems/mruby-random/src/random.c @@ -240,6 +240,80 @@ mrb_ary_shuffle(mrb_state *mrb, mrb_value ary) return new_ary; } +/* + * call-seq: + * ary.sample -> obj + * ary.sample(n) -> new_ary + * + * Choose a random element or +n+ random elements from the array. + * + * The elements are chosen by using random and unique indices into the array + * in order to ensure that an element doesn't repeat itself unless the array + * already contained duplicate elements. + * + * If the array is empty the first form returns +nil+ and the second form + * returns an empty array. + */ + +static mrb_value +mrb_ary_sample(mrb_state *mrb, mrb_value ary) +{ + mrb_int n = 0; + mrb_bool given; + mt_state *random = NULL; + mrb_int len = RARRAY_LEN(ary); + + mrb_get_args(mrb, "|i?d", &n, &given, &random, &mt_state_type); + if (random == NULL) { + mrb_value random_val = mrb_const_get(mrb, + mrb_obj_value(mrb_class_get(mrb, "Random")), + mrb_intern_lit(mrb, "DEFAULT")); + random = (mt_state *)DATA_PTR(random_val); + } + mrb_random_rand_seed(mrb, random); + mt_rand(random); + if (!given) { /* pick one element */ + switch (len) { + case 0: + return mrb_nil_value(); + case 1: + return RARRAY_PTR(ary)[0]; + default: + return RARRAY_PTR(ary)[mt_rand(random) % len]; + } + } + else { + mrb_value result; + mrb_int i, j; + + if (n < 0) mrb_raise(mrb, E_ARGUMENT_ERROR, "negative sample number"); + if (n > len) n = len; + result = mrb_ary_new_capa(mrb, n); + for (i=0; i<n; i++) { + mrb_int r; + + for (;;) { + retry: + r = mt_rand(random) % len; + + for (j=0; j<i; j++) { + if (mrb_fixnum(RARRAY_PTR(result)[j]) == r) { + goto retry; /* retry if duplicate */ + } + } + break; + } + RARRAY_PTR(result)[i] = mrb_fixnum_value(r); + RARRAY_LEN(result)++; + } + for (i=0; i<n; i++) { + RARRAY_PTR(result)[i] = RARRAY_PTR(ary)[mrb_fixnum(RARRAY_PTR(result)[i])]; + } + return result; + } +} + + void mrb_mruby_random_gem_init(mrb_state *mrb) { struct RClass *random; @@ -259,6 +333,7 @@ void mrb_mruby_random_gem_init(mrb_state *mrb) mrb_define_method(mrb, array, "shuffle", mrb_ary_shuffle, MRB_ARGS_OPT(1)); mrb_define_method(mrb, array, "shuffle!", mrb_ary_shuffle_bang, MRB_ARGS_OPT(1)); + mrb_define_method(mrb, array, "sample", mrb_ary_sample, MRB_ARGS_OPT(2)); mrb_const_set(mrb, mrb_obj_value(random), mrb_intern_lit(mrb, "DEFAULT"), mrb_obj_new(mrb, random, 0, NULL)); |