[REBOL] Re: Fast way to remove all non-numerical chars from a string
From: pwawood::gmail::com at: 22-Sep-2007 11:32
In addition to Carl's solution, you could try parse, based on Romano's
advice that "if you want speed, parse is your friend".
>> input-string: "(250) 764-0929"
== "(250) 764-0929"
;; Create a bitset! of numeric digits to use in parse
>> digit: charset [#"0" - #"9"]
== make bitset! #{
000000000000FF03000000000000000000000000000000000000000000000000
}
;; create a string! the length of the input-string in which to collect
the output
>> output-string: make string! length? input-string
== ""
;; parse the input-string to collect only numeric digits
>> parse input-string [ any [ copy next-digit digit (insert tail
output-string next-digit) | skip]]
== true
;;check the result
>> probe output-string
2507640929
== "2507640929"
If all your strings are very long, it might be worth using a temporary
hash! in which to collect the digits within the parse and then convert
it to a string afterwards. (The only problem with using hash! is that
it has been removed from Rebol 3 and I don't know enough to tell if it
successor can be used in the same way).
>> temp: make hash! length? input-string
== make hash! []
>> parse input-string [ any [ copy next-digit digit (insert tail temp
next-digit) | skip]]
== true
>> output-string: to string! temp
== "2507640929"
I haven't compared the speed of the two approaches.
Regards
Peter
On Saturday, September 22, 2007, at 06:45 am, Kai Peters wrote:
