CODEWITHSUNDEEP
regexrebolred-lang
rnso
rnso

Reputation: 24535

Remove special characters from string in Red language

I want to remove all characters in a string except:

On linux command line, using sed I would do this:

$ echo "testing-#$% yes.no" | sed 's/[^-_.a-zA-Z0-9 ]//g'

Output: 

testing- yes.no

How can I achieve the same effect in Red language with PARSE? I looked at:

However, I could not codify it. I tried: 

>> parse "mystring%^&" [#a - #z #A - #Z #0 - #9]
== false
>> parse "mystring%^&" [#a-#z#A-#Z#0-#9]        
== false

Upvotes: 6

Views: 288

Answers (3)

draegtun
draegtun

Reputation: 22560

An alternative solution to PARSE would be to use REPLACE here with a COMPLEMENT CHARSET:

replace/all "mystring%^&" complement charset [{-_. } #"a" - #"z" #"0" - #"9"] {}

NB. Above works in Rebol (2 & 3). Unfortunately it currently hangs in Red (tested on 0.63 on MacOS).

Upvotes: 2

rgchris
rgchris

Reputation: 3718

First note the difference between ISSUE! and CHAR!

#a #b #c  ; issues
#"a" #"b" #"c"   ; chars

You can then establish a character set (BITSET! type) either for the characters you want to keep or those you wish to discard. We'll do the former here:

good-chars: charset [#"a" - #"z" #"A" - #"Z" #"0" - #"9"]

Now that we have that, we can approach this in some different ways:

Parse

A fairly basic parse loop—skips any good-chars and removes anything else.

parse "mystring%^&" [any [some good-chars | remove skip]]

Remove-Each

Hopefully self-explanatory:

remove-each char "mystring%^&" [not find good-chars char]

Upvotes: 6

rebolek
rebolek

Reputation: 1301

First, characters must be in quotes, #a is issue!, char! is #"a". You've got the specification right, but you must pass it to charset function, to make a bitset! form it.

Then you can parse your string, keeping valid characters and skiping invalid:

>> chars: charset [#"a" - #"z" #"A" - #"Z" #"0" - #"9"]
== make bitset! #{000000000000FFC07FFFFFE07FFFFFE0}
>> rejoin parse "mystring%^&asdf" [collect some [keep chars | skip]]
== "mystringasdf"

Upvotes: 4

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