I have been reading _The Ruby Way_ and am confused by the temperature
conversion sample program on page 14.
The line in question is
abort "#{temp} is not a valid number." if temp !~ /-?\d+/
What I do not understand is that if \d matches "digits", which I
understand to be [0-9], how can this expression match "98.6", which it
seems to do just fine.
Thank you in advance for the clarification.
(I have the 2nd Edition of _The Ruby Way_, First Printing. I have run
the example using ruby 1.8.5 (2007-03-13 patchlevel 35) [i386-linux]).
I have been reading _The Ruby Way_ and am confused by the temperature
conversion sample program on page 14.
The line in question is
abort "#{temp} is not a valid number." if temp !~ /-?\d+/
What I do not understand is that if \d matches "digits", which I
understand to be [0-9], how can this expression match "98.6", which it
seems to do just fine.
Hi,
Since that regexp isn't anchored, it only cares whether a digit
appears anywhere in the string.
It would be happy with "abc1def".
If you anchor it, like: /\A-?\d+\z/
Then it will require an exact match, caring about all characters
between the beginning and end of the string.
I have been reading _The Ruby Way_ and am confused by the temperature
conversion sample program on page 14.
The line in question is
abort "#{temp} is not a valid number." if temp !~ /-?\d+/
What I do not understand is that if \d matches "digits", which I
understand to be [0-9], how can this expression match "98.6", which it
seems to do just fine.
Thank you in advance for the clarification.
Well I guess you are a bright student.
The regexp part has been nicely answered by Bill and it follows that a
regular expression allowing for all kind of different string
representations of Floats is quite
complex.
Why not let ruby do the work for us
May I introduce you to this idiom:
Float( temp ) rescue abort temp << " is not a valid number."
Cheers
Robert
···
On 4/17/07, mwmarkland@yahoo.com <mwmarkland@gmail.com> wrote:
(I have the 2nd Edition of _The Ruby Way_, First Printing. I have run
the example using ruby 1.8.5 (2007-03-13 patchlevel 35) [i386-linux]).
Matt
--
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw
