From: William Djaja Tjokroaminata <billtj@...>
Date: 2002-09-27T08:58:37+09:00
Subject: Re: Ruby - common pitfalls?

Hi,

I just created this list starting one hour ago.  Not to create lengthy
discussions, please send any comment directly to me via e-mail.  Thanks.

Regards,

Bill

Things That Newcomers to Ruby Should Know
=========================================

1) Use "ruby -w" instead of simply "ruby" to get helpful warnings.

2) The String#[Fixnum] method does not return the "character" (which is a
string of length one) at the Fixnum position, but instead the character
code at the position (however, this may change in the future).  Currently,
to get the character, use String#[Fixnum,1] instead.

3) Be aware of the lexical scoping interaction between local variables and
block local variables.  If a local variable is already defined before the
block, then the block will use (and quite possibly) modify the local
variable; in this case the block does not introduce a new scope.

4) In Ruby, there are two sets of logical operators: [!, &&, ||] and [not,
and, or].  [!, &&, ||]'s precedence is higher than the assignments (=, %=,
~=, /=, etc.) while [not, and, or]'s precedence is lower.  Also note that
while &&'s precedence is higher than ||'s, the and's precedence is the
same as the or's.

5) In the case statement

    case obj
    when obj1
        ....

it is the "===" method which is invoked, not the "==" method.  Also, the
order is "obj1 === obj" and not "obj === obj1".

6) Array.new (2, Hash.new) returns an array with two elements referencing
the same, indentical hash, and not two independent hashes.

7) After reading data from a file and putting them into variables, the
data type is really String.  To convert them into numbers, use the
"to_i" or "to_f" methods.  If you use the "+" operator to add the
"numbers" without calling the conversion methods, for example, you will
simply concatenate the strings.

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