/*
 *  call-seq:
 *     define_method(symbol, method)     => new_method
 *     define_method(symbol) { block }   => proc
 *  
 *  Defines an instance method in the receiver. The _method_
 *  parameter can be a +Proc+ or +Method+ object.
 *  If a block is specified, it is used as the method body. This block
 *  is evaluated using <code>instance_eval</code>, a point that is
 *  tricky to demonstrate because <code>define_method</code> is private.
 *  (This is why we resort to the +send+ hack in this example.)
 *     
 *     class A
 *       def fred
 *         puts "In Fred"
 *       end
 *       def create_method(name, &block)
 *         self.class.send(:define_method, name, &block)
 *       end
 *       define_method(:wilma) { puts "Charge it!" }
 *     end
 *     class B < A
 *       define_method(:barney, instance_method(:fred))
 *     end
 *     a = B.new
 *     a.barney
 *     a.wilma
 *     a.create_method(:betty) { p self }
 *     a.betty
 *     
 *  <em>produces:</em>
 *     
 *     In Fred
 *     Charge it!
 *     #<B:0x401b39e8>
 */

static VALUE
rb_mod_define_method(argc, argv, mod)
    int argc;
    VALUE *argv;
    VALUE mod;
{
    ID id;
    VALUE body;
    NODE *node;
    int noex;

    if (argc == 1) {
        id = rb_to_id(argv[0]);
        body = proc_lambda();
    }
    else if (argc == 2) {
        id = rb_to_id(argv[0]);
        body = argv[1];
        if (!rb_obj_is_method(body) && !rb_obj_is_proc(body)) {
            rb_raise(rb_eTypeError, "wrong argument type %s (expected Proc/Method)",
                     rb_obj_classname(body));
        }
    }
    else {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }
    if (RDATA(body)->dmark == (RUBY_DATA_FUNC)bm_mark) {
        node = NEW_DMETHOD(method_unbind(body));
    }
    else if (RDATA(body)->dmark == (RUBY_DATA_FUNC)blk_mark) {
        struct BLOCK *block;

        body = proc_clone(body);
        Data_Get_Struct(body, struct BLOCK, block);
        block->frame.last_func = id;
        block->frame.orig_func = id;
        block->frame.last_class = mod;
        node = NEW_BMETHOD(body);
    }
    else {
        /* type error */
        rb_raise(rb_eTypeError, "wrong argument type (expected Proc/Method)");
    }

    noex = NOEX_PUBLIC;
    if (ruby_cbase == mod) {
        if (SCOPE_TEST(SCOPE_PRIVATE)) {
            noex = NOEX_PRIVATE;
        }
        else if (SCOPE_TEST(SCOPE_PROTECTED)) {
            noex = NOEX_PROTECTED;
        }
    }
    rb_add_method(mod, id, node, noex);
    return body;
}