Sometime I saw you wrote regex =~ string, while sometime you wrote
string =~ regex.
What’s their difference and what’s the recommended way? Thanks.
Jenn.
On 01/04/2010 10:27 AM, Ruby N. wrote:
Sometime I saw you wrote regex =~ string, while sometime you wrote
string =~ regex.
What’s their difference and what’s the recommended way? Thanks.
The first version invokes method Regexp#=~ and the second version
invokes String#=~ - which happen to do roughly the same although I
believe the second one to be a tad slower. I personally prefer the
first form because of the speed difference and regular expression
matching is rather an operation of Regexp than of String.
Kind regards
robert
On Mon, Jan 4, 2010 at 6:20 AM, Robert K.
[email protected] wrote:
The first version invokes method Regexp#=~ and the second version invokes
String#=~ - which happen to do roughly the same although I believe the
second one to be a tad slower. I personally prefer the first form because
of the speed difference and regular expression matching is rather an
operation of Regexp than of String.
Very technically speaking, calling the Regexp#=~ will be
microscopically faster because it avoids a tiny bit of C code that
gets executed when calling the String#=~ version. In practice though,
the difference is so small as to be invisible against the noise of the
rest of the system.
String#=~ just has a little sugar built in.
If it’s passed a Regexp, then it just calls the C function underlying
Regexp#=~.
If it is passed a String, it complains.
If it is passed anything else, it tries to call #=~ on what it was
passed, passing itself as the argument. This lets one build custom
matching classes that Strings can use with the =~ syntax.
Kirk H.
Robert K. wrote:
On 01/04/2010 10:27 AM, Ruby N. wrote:
Sometime I saw you wrote regex =~ string, while sometime you wrote
string =~ regex.
What’s their difference and what’s the recommended way? Thanks.The first version invokes method Regexp#=~ and the second version
invokes String#=~ - which happen to do roughly the same although I
believe the second one to be a tad slower. I personally prefer the
first form because of the speed difference and regular expression
matching is rather an operation of Regexp than of String.
Interesting. Whereas I prefer the second because I think
mystring =~ /foo/
is syntactically analogous to
mystring == ‘foo’
Kind regards
robert
Best,
–Â
Marnen Laibow-Koser
http://www.marnen.org
[email protected]