Method prototypes like C++? // Compiling executables

Hi, I’m switching from C++ to Ruby, I have a few questions.

  1. How come there isn’t any “method prototype” feature like the function
    prototypes in C++? Like, in c++ I declared just the name of a funcion at
    the beginning of a block of code and then I could put the function
    anywhere in the program, so it could be called wherever, without
    worrying if it had been fully declared or not. Is this possible?

  2. I find it awesome that you needn’t compile to view the results of
    your code; still, i would like to be able to compile my programs to an
    executable file for distribution. Is it possible?

  3. I still don’t get how this whole “gems” thing work. In C++ I used to
    load libraries, it seems that in Ruby most of the libraries are loaded
    by themselves when needed. When exactly do I need to include other
    libraries?

Also, I forgot:

  1. In C++ I used to use “labels” to redirect quickly to small chunks of
    code when making a whole function seemed useless; or when I wanted to
    reask a question if the user input was not recognised. I know their use
    is deprecated, In fact I was able to do just what i did before with
    methods and exception handling.
    Just for asking, there is no label-like feature in Ruby, isn’t it?

On Feb 18, 2010, at 8:50 AM, Claudio F. wrote:

Hi, I’m switching from C++ to Ruby, I have a few questions.

  1. How come there isn’t any “method prototype” feature like the
    function
    prototypes in C++? Like, in c++ I declared just the name of a
    funcion at
    the beginning of a block of code and then I could put the function
    anywhere in the program, so it could be called wherever, without
    worrying if it had been fully declared or not. Is this possible?

Sure just do it! Methods only need to exist when then are “called”
and even then you can use the method_missing hook to define them on
the fly if you need to.

  1. I find it awesome that you needn’t compile to view the results of
    your code; still, i would like to be able to compile my programs to an
    executable file for distribution. Is it possible?

Look at JRuby’s ability to create .class files for the JVM, but you
might want to keep an open mind about whether you really need to
compile.

  1. I still don’t get how this whole “gems” thing work. In C++ I used
    to
    load libraries, it seems that in Ruby most of the libraries are loaded
    by themselves when needed. When exactly do I need to include other
    libraries?

It’s a way to have multiple versions of libraries on your system.
You’ll know you need more because something doesn’t exist. For
example, there are some useful methods on Date that are only available
if you “require ‘date’” in your code. (Not the best example because
that’s not a gem, but a standard library, i.e., it comes as part of
Ruby.)

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

how to unsubscribe from this mailing list can any one please reply me.

thanks
sandeep

On Thu, Feb 18, 2010 at 6:28 PM, Claudio F. [email protected]
wrote:

void function() {

def method
print (‘The method has been executed’)
end

it just prints me nothing; I think it has something to do with ruby’s
dynamic definitions.

Just how to achieve the same thing in ruby? (summoning a function that
is declared later in the code)

What Rob wanted to say is that you don’t need to declare a function
(method). You just call it, and it has to have been defined before the
call. But be aware that the code inside a method is not executed when
it’s parsed, only when the method is called, so you can have this:

irb(main):001:0> def caller
irb(main):002:1> method(“a”)
irb(main):003:1> end
=> nil
irb(main):004:0> def method(s)
irb(main):005:1> puts s
irb(main):006:1> end
=> nil
irb(main):007:0> caller
a

You can have the definition of caller before the definition of method.
What you can’t do is call caller before defining method.

Hope this clears up a bit,

Jesus.

2010/2/18 Claudio F. [email protected]:

void function() {
cout<<“The function has been executed”
}

And it would still print “The function has been executed”

You need that in C / C++ only because implementations are split to
header and source files. We don’t do that in Ruby. Instead, we
implement whatever functionality we need and place it in one or more
.rb files. Those are then read by using “require”.

it just prints me nothing; I think it has something to do with ruby’s
dynamic definitions.

Just how to achieve the same thing in ruby? (summoning a function that
is declared later in the code)

That’s not a problem as long as execution starts later:

def foo
method
end

def method
puts ‘It works!’
end

foo

This is typically the case if your required files contain declarations
only.

Kind regards

robert

Rob B. wrote:

Sure just do it! Methods only need to exist when then are “called”
and even then you can use the method_missing hook to define them on
the fly if you need to.

Wait, I explain my problem.
In C++ I would have been able to to this:

void function();
function();
void function() {
cout<<“The function has been executed”
}

And it would still print “The function has been executed”

In ruby instead if I do this:

def method; end

method

def method
print (‘The method has been executed’)
end

it just prints me nothing; I think it has something to do with ruby’s
dynamic definitions.

Just how to achieve the same thing in ruby? (summoning a function that
is declared later in the code)

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