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Hi *,

could you help me please ? I'm trying to write a code where I could have
operators' functions as values of hash and executing them in way like this
(formal code):

#=============================
operators = { "+" => Fixnum.+,
"-" => Fixnum.-,
"++" => Myclass.++}

op = "+"

result = operators[op](left,right) if left.class==Fixnum and right.class==Fixnum
#============================

is it possible ? Thanks,

Cheers,

V.

[Note: parts of this message were removed to make it a legal post.]


On 2008.11.15., at 11:56, Vladimir Fekete wrote:

> Hi *,
>
> could you help me please ? I'm trying to write a code where I could
> have
> operators' functions as values of hash and executing them in way
> like this
> (formal code):
>
> #=============================
> operators = { "+" => Fixnum.+,
> "-" => Fixnum.-,
> "++" => Myclass.++}
>
> op = "+"
>
> result = operators[op](left,right) if left.class==Fixnum and
> right.class==Fixnum
> #============================

++ is not supported by Ruby

I would do

1.send '+'.to_sym, 2

unless you want to use some esoteric operator mappings, you don't need
the hash.
Fixnum.+ doesn't make that much sense because of Ruby's duck typing
(and why would you want to restrict yourself to work with just certain
objects?)

p.s.: dobre tu vidiet matfyzaka

Cheers,
Peter
___
http://www.rubyrailways.com

2008/11/15 Vladimir Fekete <>:
> Hi *,
>
> could you help me please ? I'm trying to write a code where I could have
> operators' functions as values of hash and executing them in way like this
> (formal code):
>
> #=============================
> operators = { "+" => Fixnum.+,
> "-" => Fixnum.-,
> "++" => Myclass.++}
>
> op = "+"
>
> result = operators[op](left,right) if left.class==Fixnum and right.class==Fixnum
> #============================
>
> is it possible ? Thanks,

Use send, if all operators are binary:

left.send(:+, right)
left.send(:-, right)

etc.

Stefan

Vladimir Fekete wrote:
> operators =3D { "+" =3D> Fixnum.+,
> "-" =3D> Fixnum.-,

"+" =3D> Fixnum.instance_method(:+),
"-" =3D> Fixnum.instance_method(,

> =A0 =A0 =A0 =A0 =A0 =A0 =A0 "++" =3D> Myclass.++}

There is no ++ operator in ruby and you can't define one.


> op =3D "+"
>
> result =3D operators[op](left,right) =A0if left.class=3D=3DFixnum and
> right.class=3D=3DFixnum

result =3D operators[op].bind(left).call(right) if left.is_a?(Fixnum) and=20
right.is_a?(Fixnum)


Or you skip the whole thing with the hash and just do:

op =3D "+"
result =3D left.send(op, right)


HTH,
Sebastian
=2D-=20
Jabber:
ICQ: 205544826

On Sat, Nov 15, 2008 at 08:07:17PM +0900, Sebastian Hungerecker wrote:
> Vladimir Fekete wrote:
> > operators = { "+" => Fixnum.+,
> > "-" => Fixnum.-,
>
> "+" => Fixnum.instance_method(:+),
> "-" => Fixnum.instance_method(,
>
> > ? ? ? ? ? ? ? "++" => Myclass.++}
>
> There is no ++ operator in ruby and you can't define one.

it's Myclasses ++ operator

>
>
> > op = "+"
> >
> > result = operators[op](left,right) ?if left.class==Fixnum and
> > right.class==Fixnum
>
> result = operators[op].bind(left).call(right) if left.is_a?(Fixnum) and
> right.is_a?(Fixnum)
>
>
> Or you skip the whole thing with the hash and just do:
>
> op = "+"
> result = left.send(op, right)
>
>
> HTH,
> Sebastian
> --
> Jabber:
> ICQ: 205544826
>
>

What I'm trying to do is Domain specific language class, for which I could set
up names of variables, functions and operators and then parse and execute
a string (f.e. "( a + ( b * c ) + sin ( d ) )", where
variables could be hash { "a" => 1, "b" => 2, "c" => 3, "d" => 4} and
functions could be hash again so naturaly I asked whether it is possible to
make it with operators). I tryied to use som ruby's or irb's native
DSL but withouth success.

V.

Vladimir Fekete wrote:
> it's Myclasses ++ operator

You can't define ++ on any class. You just can't. If the parser sees ++
anywhere it interprets it as two calls to +@ or one call to + and one to +@.

HTH,
Sebastian
--
NP: Dire Straits - Your Latest Trick
Jabber:
ICQ: 205544826