Re: Regular Expressions

[Wayne Landsman <landsman(at)mpb.gsfc.nasa.gov>]

"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.