From: ts <decoux@...>
Date: 2001-09-26T15:26:23+09:00
Subject: [ruby-talk:21709] Re: Extension Question: Block Parameters

>>>>> "J" == Jason Voegele <jason@jvoegele.com> writes:

J> If a block is provided, the foo method should pass along the block to
J> the bar method.  I couldn't find any documentation on this.

 You can use the parameter "&" to rb_scan_args(), for example :

     VALUE block;
     rb_scan_args(argc, argv, "0&", &block);

 in this case ruby will just do :

     block = Qnil;
     if (rb_block_given_p()) {
        block = rb_f_lambda();
     }

 perhaps faster to write it rather than call rb_scan_args() :-))

 A more generic way to write it, is something like this (it's important to
 call rb_iterate() to propagate the block)

pigeon% cat tt.c
#include <ruby.h>

static VALUE
tt_bar(argc, argv, obj)
    int argc;
    VALUE obj, *argv;
{
    if (rb_block_given_p()) {
        VALUE tt = INT2FIX(12);
        if (argc) {
            tt = argv[0];
        }
        rb_yield(tt);
    }
    return obj;
}

static VALUE
tt_iter(tmp)
    VALUE *tmp;
{
    return rb_funcall2(tmp[2], rb_intern("bar"), (int)tmp[0], (VALUE *)tmp[1]);
}

static VALUE
tt_yield(obj, res)
    VALUE obj, res;
{
    rb_ary_push(res, rb_yield(obj));
    return Qnil;
}

static VALUE
tt_foo(argc, argv, obj)
    int argc;
    VALUE obj, *argv;
{
    if (rb_block_given_p()) {
        VALUE res, tmp[3];
        tmp[0] = (VALUE)argc;
        tmp[1] = (VALUE)argv;
        tmp[2] = obj;
        res = rb_ary_new();
        rb_iterate(tt_iter, (VALUE)tmp, tt_yield, res);
        return res;
    }
    return Qnil;
}

void Init_tt()
{
    VALUE tt_cTt = rb_define_class("Tt", rb_cObject);
    rb_define_method(tt_cTt, "foo", tt_foo, -1);
    rb_define_method(tt_cTt, "bar", tt_bar, -1);
}
pigeon% 

pigeon% cat b.rb
#!/usr/bin/ruby
require 'tt'
a = Tt.new.foo { |i| puts i; i * 12 }
p a
pigeon% 

pigeon% b.rb
12
[144]
pigeon% 



Guy Decoux