add "has_key?" and aliases.

README.md

@@ -7,7 +7,8 @@ for environment variables.
 ### Methods
 
 ```
-[] []= clear delete inspect keys size store to_a to_hash to_s values
+[] []= clear delete has_key? include? inspect key? keys
+member? size store to_a to_hash to_s values
 ```
 
 

mrblib/env.rb

@@ -0,0 +1,5 @@
+class << ENV
+  alias include? has_key?
+  alias key? has_key?
+  alias member? has_key?
+end

src/env.c

@@ -120,6 +120,20 @@ mrb_env_aget(mrb_state *mrb, mrb_value self)
   return mrb_env_getenv(mrb, key);
 }
 
+mrb_value
+mrb_env_has_key(mrb_state *mrb, mrb_value self)
+{
+  mrb_value name;
+  const char *key;
+  mrb_get_args(mrb, "S", &name);
+  key = mrb_str_to_cstr(mrb, name);
+  if (getenv(key) != NULL) {
+    return mrb_true_value();
+  } else { 
+    return mrb_false_value();
+  }
+}
+
 mrb_value
 mrb_env_keys(mrb_state *mrb, mrb_value self)
 {
@@ -282,6 +296,7 @@ mrb_mruby_env_gem_init(mrb_state *mrb)
   mrb_define_singleton_method(mrb, e,"[]=",      mrb_env_aset,       MRB_ARGS_REQ(2));
   mrb_define_singleton_method(mrb, e,"clear",    mrb_env_clear,      MRB_ARGS_NONE());
   mrb_define_singleton_method(mrb, e,"delete",   mrb_env_delete,     MRB_ARGS_REQ(1));
+  mrb_define_singleton_method(mrb, e,"has_key?", mrb_env_has_key,    MRB_ARGS_REQ(1));
   mrb_define_singleton_method(mrb, e,"inspect",  mrb_env_inspect,    MRB_ARGS_NONE());
   mrb_define_singleton_method(mrb, e,"keys",     mrb_env_keys,       MRB_ARGS_NONE());
   mrb_define_singleton_method(mrb, e,"size",     mrb_env_size,       MRB_ARGS_NONE());

test/env_test.rb

@@ -68,6 +68,12 @@ def test_env_to_s
       assert_equal("ENV", ENV.to_s)
     end
 
+    def test_env_has_key
+      set_dummy_env
+      assert_true  ENV.has_key?("FOO")
+      assert_false ENV.has_key?("BAR")
+    end
+
     def test_env_inspect
       set_dummy_env
       assert_equal("{\"FOO\"=>\"bar\"}", ENV.inspect)