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Hi!

What's the best way to test if a string only consists of whitespaces and
newlines?

best I could come up with is


class String

def is_whitespace_only?
strings_to_test = split("\n")
whitespace = /^\s+$/
is_whitespace_only = true
strings_to_test.each{ |str|
unless whitespace.match(str) or str.empty?
is_whitespace_only = false
break
end
}
is_whitespace_only
end

end

But somehow I think there should be a better way to do it. Any ideas?
Is it okay to add such methods to class String itself?

Any advices appreciated.

regards,
Henrik

def only_whitespace?
each_byte { |b| return false if b != 32 }
true
end


On Thu, 2004-09-23 at 00:54, Henrik Horneber wrote:
> Hi!
>
> What's the best way to test if a string only consists of whitespaces and
> newlines?
>
> best I could come up with is
>
>
> class String
>
> def is_whitespace_only?
> strings_to_test = split("\n")
> whitespace = /^\s+$/
> is_whitespace_only = true
> strings_to_test.each{ |str|
> unless whitespace.match(str) or str.empty?
> is_whitespace_only = false
> break
> end
> }
> is_whitespace_only
> end
>
> end
>
> But somehow I think there should be a better way to do it. Any ideas?
> Is it okay to add such methods to class String itself?
>
> Any advices appreciated.
>
> regards,
> Henrik
>

I think regexp should be is faster than each_byte. What about this?

class String

def whitespace_only? str
str.split(/\n/).each { |x|
return false unless x =~ /^\s*$/
}
true
end

end


MiG

I highly doubt a regex is faster than each_byte. each_byte has very
little code and is very fast (looping over the array in C and casting
the chars to fixnums), where as with a regex it has to pass through the
regex parser, get pulled back out as an object, pushed back into split,
which there in turn returns a potentially huge array which you pull back
again to run over with each. Then you've done another comparison with a
regex within the block which i guarantee is much slower then comparing 2
Fixnums.

My initial version didnt do \n, only white space, so here's my updated
version that even does tabs.

class String
def only_ws?
each_byte { |b| return false unless [9,10,32].include?(b) }
true
end
end

Evan Webb //


On Thu, 2004-09-23 at 01:11, MiG wrote:
> I think regexp should be is faster than each_byte. What about this?
>
> class String
>
> def whitespace_only? str
> str.split(/\n/).each { |x|
> return false unless x =~ /^\s*$/
> }
> true
> end
>
> end
>
>
> MiG
>

On Thursday 23 September 2004 03:54 am, Henrik Horneber wrote:
> Hi!
>
> What's the best way to test if a string only consists of whitespaces and
> newlines?

Unless you're being more specific:

str.strip.length == 0

Also matching against something like

/\A\s*\z/m

but I'm no Regexp expert by a long shot

T.

--
( o _ カラ�
// trans.
/ \

I don't give a damn for a man that can only spell a word one way.
-Mark Twain

"Henrik Horneber" <> schrieb im Newsbeitrag
news:...
> Hi!
>
> What's the best way to test if a string only consists of whitespaces and
> newlines?
>
> best I could come up with is
>
>
> class String
>
> def is_whitespace_only?
> strings_to_test = split("\n")
> whitespace = /^\s+$/
> is_whitespace_only = true
> strings_to_test.each{ |str|
> unless whitespace.match(str) or str.empty?
> is_whitespace_only = false
> break
> end
> }
> is_whitespace_only
> end
>
> end
>
> But somehow I think there should be a better way to do it. Any ideas?
> Is it okay to add such methods to class String itself?
>
> Any advices appreciated.
>
> regards,
> Henrik
>
>

>> rx = %r{\A\s*\z}
=> /\A\s*\z/
>> rx =~ ""
=> 0
>> rx =~ " "
=> 0
>> rx =~ " a"
=> nil
>> rx =~ " \n a"
=> nil
>> rx =~ " \n "
=> 0
>> rx =~ " \n \n"
=> 0

Regards

robert

Hi!


> if "#{s}".chomp.strip.length == 0

...

> rx = %r{\A\s*\z}


Obviously there is more than one way to do it ...and all are better than
mine.

Thanks everybody!

Henrik Horneber <> writes:

> Hi!
>
> What's the best way to test if a string only consists of whitespaces
> and newlines?

class String
def is_whitespace_only?
self !~ /[\s\n]/m
end
end

>>>>> "M" == Mikael Brockman <> writes:

M> self !~ /[\s\n]/m

1) \n is in \s with a character class, /m is useless
2) you are testing that it don't exist a whitespace character in the string


Guy Decoux

ts <> writes:

> >>>>> "M" == Mikael Brockman <> writes:
>
> M> self !~ /[\s\n]/m
>
> 1) \n is in \s with a character class, /m is useless
> 2) you are testing that it don't exist a whitespace character in the string

self !~ /[^\s]/