From: "Bermejo, Rodrigo" <rodrigo.bermejo@...>
Date: 2004-02-10T04:12:54+09:00
Subject: Re: evaluate and print an expression

 

def evaluate(code)
   puts "#{code}==>"
   eval code
end

evaluate("1+2==3")

1+2==3 ==>
true




Piergiuliano Bossi wrote:

> I hope that what I'm asking doesn't sound too weird, but I'm trying to 
> understand if in ruby is possible to print and evaluate an expression 
> at the same time. I know for example that I can do like this:
>
> irb(main):001:0> expr = "1+2==3"
> => "1+2==3"
> irb(main):002:0> puts expr + ' ==> ' + (eval expr).to_s
> 1+2==3 ==> true
> => nil
>
> What I don't like is to specify the expression as a string. I'd rather 
> prefer to manage code directly, but I don't know exactly how to print 
> it and evaluate it at the same time. Ideally, I'd like to change the 
> following code in order to print block body:
>
> irb(main):012:0> def evaluate(&code)
> irb(main):013:1>   p code
> irb(main):014:1>   code.call
> irb(main):015:1> end
> => nil
> irb(main):016:0> evaluate { 1+2==3 }
> #<Proc:0x02a4ea78@(irb):16>
> => true
>
> Do you see what I mean? Instead of having:
>     #<Proc:0x02a4ea78@(irb):16>
> I'd like to get:
>     { 1+2==3 }
> or something like that.
>
> I know that in lisp this can be easily done due to its nature (that 
> is, code is data and data is code), but in ruby?
>
> Thanks for your help!
> Ciao, Giuliano
>