On 25 January 2013 13:16, Scott Price &l= t;lists@ruby-foru= m.com> wrote:

-- Can sombody please break these down and let me know wha= t each line of
these examples are doing. I've used c++ a little, but I'm new to Ru= by.
Any response would be greatly appreciated.

=A0

First, a question: where did you find this code? It's not what= we could consider "typical Ruby," in fact it looks a lot like wh= at a C/C++ programmer would write. =A0As such, seeing as you've "u= sed C++ a little," surely you could work out what is going on?

Anyway, I'll break down a function or t= wo the way I understand the interpreter to work (note: not necessarily how = any of them _actually_ work) in case it's helpful.

def pow(base, exponent)

Define = a method called 'pow'.

It has two named parameters, called 'base' and 'expo= nent'.

Given the context I can't say for sure on wh= ich object this method is defined, but for the sake of tutorial, for now le= t's just say it's a "global" function.

=A0 result =3D 1

Create a variable called 'r= esult', and assign to it the value 1. =A0Under the hood I'd interpr= et that as: make the 'result' variable refer to the singleton Fixnu= m object '1'

=A0

=A0 i =3D 1

Ditto, but called 'i'

<= div style>=A0

=A0 while i <=3D exponent

Invoke the method &= #39;<=3D' on the object referred to by variable 'i', with it= s parameter being the object referred to by variable 'exponent'.

See: =A0Fixnum#<=3D =A0<http://www.ruby-doc.org/core-1.9.3/= Fixnum.html#method-i-3C-3D>

Use= the result (return value) of that method as the condition in a 'while&= #39; expression.

=A0

=A0 =A0 result =3D result * base

Invoke the meth= od '*' on the object referred to by variable 'result', with= its parameter being the object referred to by variable 'base'.

See: =A0 Fixnum#* =A0<http://www.ruby-doc.org/core-1.9.3/Fixnum.h= tml#method-i-2A>

Assign the result of= that method to the 'result' variable. =A0(i.e. update the 'res= ult' variable to point to the object returned from #* )

=A0 =A0 i +=3D 1

Syntactic sugar for: =A0`i =3D = i + 1`

Invoke the method '+' on= the object referred to by variable 'i', with its parameter being t= he single Fixnum object '1'.

See: =A0 Fixnum#+ =A0<http://www.ruby-doc.org/core-1.9.3/Fixnum.html#me= thod-i-2B>

Assign the result of that method= to the 'i' variable. =A0(I.e. update the 'i' variable to p= oint to the object returned from #+ )

=A0

=A0 end

Marks the end of the current scope/block= /whatever you want to call it.

In this case implies an exec= ution jump back to the 'while' statement three lines above.

=A0

=A0 result

end

= These two lines go hand-in-hand. =A0The former is a simple statement which = evaluates to the value of the 'result' variable.

'end' again marks the end of the current scope/block/etc= ., in this case the chunk of code that started with 'def'. =A0I.e. = it indicates the end of the function.

Since the value of a = chunk of code is always the value of the last expression evaluated in it, a= nd the last expression in this function was the 'result' bit, the r= eturn value of this function is the final value of the 'result' var= iable.

Note: a regular rubyist would probably just write= : =A0`base ** exponent`

Actually, I won'= t write out the others, because I don't have time. =A0Hopefully this ha= s been illuminating in some way. =A0And if I've gotten anything wrong, = someone please correct me.

Cheers

--
=A0 Matthew Kerwin, B= .Sc (CompSci) (Hons)
=A0 http://matthew.kerwin.net.au/
=A0 ABN: 59-013-727-651
=A0 "You'll never find a programming language that frees
=A0 you from the burden of clarifying your ideas." - xkcd