Computer Science Canada

A Challenge

Author:

wtd [ Sat Dec 24, 2005 12:14 am ]

Post subject:

A Challenge

Beyond the usual TYS questions, I have a challenge for those who consider themselves good Ruby programmers.

I have the following C function:

code:

#include <stdio.h>

void print_foo()
{
puts("foo");
}

Make it possible to call this function from Ruby. Do not modify the "print_foo" C function itself, though you may add more code to the "foo.c" source file.

code:

>> require "foo"
=> true
>> print_foo
foo
=> nil
>>

Author:

wtd [ Sat Dec 24, 2005 12:59 am ]

Post subject:

A further challenge along the same lines.

Write pure Ruby code which does the same as this Ruby extension written in C.

code:

#include <ruby.h>

static VALUE cFoo;

static VALUE foo_initialize(VALUE self)
{
rb_iv_set(self, "@bar", rb_int_new(42));
}

static VALUE foo_set_bar(VALUE self, VALUE new_val)
{
int old_bar = FIX2INT(rb_iv_get(self, "@bar"));
int new_bar = FIX2INT(new_val);

if (new_bar > old_bar)
{
rb_iv_set(self, "@bar", new_val);
}
}

void Init_foo()

{
cFoo = rb_define_class("Foo", rb_cObject);
rb_define_method(cFoo, "initialize", foo_initialize, 0);
rb_define_attr(cFoo, "bar", 1, 0);
rb_define_method(cFoo, "bar=", foo_set_bar, 1);

}

Author:

rdrake [ Sat Dec 24, 2005 8:00 pm ]

Post subject:

The first one I can get to work, but not 100% correctly.

code:

#include <stdio.h>
#include <ruby.h>

static VALUE foo_class;

void print_foo()
{
puts("foo");
}

static VALUE foo_initialize(VALUE self)
{
print_foo();
}

void Init_foo()
{
foo_class = rb_define_class("Foo", rb_cObject);
rb_define_method(foo_class, "initialize", foo_initialize, 0);
rb_define_attr(foo_class, "bar", 1, 0);
rb_define_method(foo_class, "bar", foo_initialize, 0);
}

Here's how you use it

code:

> require 'foo'
=> true
> Foo.new
foo

I think that's close enough.

It looks like the second would be something like the following.

code:

class Foo
def initialize
@bar = 42
end

def bar(new_val)
old_bar = @bar
new_bar = new_val

if new_bar > old_bar then
@bar = new_val
end
end
end

Use the following code to test it.

code:

foobar = Foo.new
foobar.bar(41)

I think that's it anyways.

Author:	wtd [ Sat Dec 24, 2005 8:14 pm ]
Post subject:
Close, but not quite.

Author:

rdrake [ Sat Dec 24, 2005 8:24 pm ]

Post subject:

How about this for the second?

code:

class Foo
def initialize
@bar = 42
end

def bar=(new_val)
old_bar = @bar
new_bar = new_val

if new_bar > old_bar then
@bar = new_val
end
end
end

Foo.new.bar=(41)

My solution to the first is posted above.

Author:

wtd [ Sat Dec 24, 2005 8:35 pm ]

Post subject:

cartoon_shark wrote:

How about this for the second?

code:

class Foo
def initialize
@bar = 42
end

def bar=(new_val)
old_bar = @bar
new_bar = new_val

if new_bar > old_bar then
@bar = new_val
end
end
end

Foo.new.bar=(41)

My solution to the first is posted above.

Very good.

Your answer to the first one is too complicated. Smile

code:

#include <stdio.h>
#include <ruby.h>

void print_foo()
{
puts("foo");
}

static VALUE wrapped_print_foo(VALUE self)
{
print_foo();
return Qnil;
}

void Init_foo()
{
rb_define_method(rb_cObject, "print_foo", wrapped_print_foo, 0);
}

Author:	wtd [ Sat Dec 24, 2005 10:34 pm ]
Post subject:
http://ruby-doc.org/doxygen/1.8.2/ruby_8h.html

Author:	rdrake [ Sun Dec 25, 2005 9:44 am ]
Post subject:
No wonder why I turned to Ruby...

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