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Re: Regular Expressions [message #24240 is a reply to message #15713]

Tue, 20 March 2001 12:14

Wayne Landsman
Messages: 117
Registered: January 1997

Senior Member

"Pavel A. Romashkin" wrote:

> Wouldn't it be easier to analyse a byte array with more human-readible
> functions, than those beautiful regular expressions you guys brought up?
>

It depends on what you mean by "easier". One nice thing about STREGEX is
that it works on vector strings. One can always convert the string
array to a byte array and analyze, but -- **if you are trying to avoid
loops** -- the indexing can be become extremely opaque, and exercise at
least as many brain cells as using STREGEX. For example, JD's solution
can also apply to a string array where one is trying to extract the
substrings beginning and ending with a singe quote:

IDL> st = ["value1 = 'Wayne''s dog' / First string ", $
"value2 = 'Sue''s dog and Ralph''s cat' / Second string ", $
"value3 = 'two pigeons'" ]

IDL> val = (stregex(st, /SUBEXPR,/EXTRACT,"= *'(.*)'([^']|$)"))[1,*]
IDL> print,val
Wayne''s dog
Sue''s dog and Ralph''s cat
two pigeons

Of course, one should probably add an English comment to the use of STRGEX

; Find the substring beginning with an "=", followed by any number of
characters,
; followed by a quote, followed by any number of characters (including
double
; quotes) up to the last single quote. Extract from this substring all
; characters between the first and last single quotes.

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[Message index]

		regular expressions By: Michael Werger on Fri, 04 June 1999 00:00
		Re: Regular expressions By: Brian Jackel on Fri, 10 November 2000 00:00
		Re: Regular expressions By: Martin Schultz on Fri, 10 November 2000 00:00
		Re: Regular expressions By: Liam E. Gumley on Fri, 10 November 2000 00:00
		Re: Regular Expressions By: John-David T. Smith on Thu, 15 March 2001 16:09
		Re: Regular Expressions By: Wayne Landsman on Thu, 15 March 2001 19:24
		Re: Regular Expressions By: John-David T. Smith on Fri, 16 March 2001 09:20
		Re: Regular Expressions By: Pavel A. Romashkin on Mon, 19 March 2001 13:52
		Re: Regular Expressions By: Craig Markwardt on Tue, 20 March 2001 15:23
		Re: Regular Expressions By: John-David T. Smith on Tue, 20 March 2001 15:28
		Re: Regular Expressions By: Mark Hadfield on Tue, 20 March 2001 14:48
		Re: Regular Expressions By: Wayne Landsman on Tue, 20 March 2001 12:14
		Re: Regular Expressions By: Martin Schultz on Tue, 20 March 2001 04:39

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