Proc.new v. lambda

ruby-talk
1

Is there a way to programmatically determine if an object was generated by Proc.new versus lambda?

2

Really, you could have checked it yourself.

irb(main):001:0> a = Proc.new{}
=> #<Proc:0xca1cb8@(irb):1>
irb(main):002:0> b = lambda{}
=> #<Proc:0x141af50@(irb):2 (lambda)>
irb(main):003:0> a.lambda?
=> false
irb(main):004:0> b.lambda?
=> true

-- Matma Rex

3

Bartosz,

Wednesday, March 7, 2012, 8:25:57 AM, you wrote:

Really, you could have checked it yourself.

irb(main):001:0>> a = Proc.new{}
=>> #<Proc:0xca1cb8@(irb):1>
irb(main):002:0>> b = lambda{}
=>> #<Proc:0x141af50@(irb):2 (lambda)>
irb(main):003:0>> a.lambda?
=>> false
irb(main):004:0>> b.lambda?
=>> true

-- Matma Rex

First you have to know there is a lambda? function.

What I did do was:
irb(main):002:0> p = Proc.new {42}
=> #<Proc:0x2916048@(irb):2>
irb(main):003:0> l = lambda {43}
=> #<Proc:0x2aceb80@(irb):3 (lambda)>
irb(main):004:0> defined? p
=> "local-variable"
irb(main):006:0> defined? l
=> "local-variable"

irb(main):007:0> p.class
=> Proc
irb(main):008:0> l.class
=> Proc

So, given there is a lambda? function, why not a proc? function?

In terms of design, why isn't lambda a super or sub class of Proc?

4

First you have to know there is a lambda? function.

It's all documented here: http://www.ruby-doc.org/core-1.9.3/Proc.html
Ruby's docs are IMO pretty good. Also, in IRB you can always call
#methods or #instance_methods to see what the object can do, for ex.

irb(main):007:0> Proc.instance_methods(false).sort # "false" means
"don't show inherited methods"
=> [:==, :===, :, :arity, :binding, :call, :clone, :curry, :dup,
:eql?, :hash, :lambda?, :parameters, :source_location, :to_proc,
:to_s, :yield]

So, given there is a lambda? function, why not a proc? function?
In terms of design, why isn't lambda a super or sub class of Proc?

These two I can't answer. I guess it could be both ways.

-- Matma Rex

···

2012/3/7 Ralph Shnelvar <ralphs@dos32.com>:

5

It is always hard to answer 'why?' with respect to design decisions.

I don't have any special insight but Ruby tends towards shallow inheritance graphs and 'wide' interfaces. Instead of Collection, Array, Stack, Queue, Dequeue, FixedArray, VariableArray, etc., there is just Array with 88 methods (ruby 1.9.3-p125).

Similarly instead of Proc and Lambda, there is just Proc.

I guess the most accurate, but perhaps unsatisfying answer, regarding the design of core Ruby classes is that they are that way because that is what Matz likes. :slight_smile:

Gary Wright

···

On Mar 7, 2012, at 11:32 AM, Ralph Shnelvar wrote:

In terms of design, why isn't lambda a super or sub class of Proc?