in reply to Re: CSV regex with hash/array program plan
in thread CSV regex with hash/array program plan

Thanks for the replies folks,

The sort of thing i had in mind is 

use feature "switch";

for (to be determined) {

when ((s/(\b[A-E]{3}\b)/XXX/g)) {@array[i,1] = $1}
when (s/((Science)|(science))/XXX/g) {@array[i,2] = $1}
when (s/((Math)|(math))/XXX/g) {@array[i,3] = $1} 
when - for all remaining subjects...
when (s/((first|First)\W+(?:\w+\W+){1,10}?([A-E]{3})) #or some similar
+ REGEX returning only the first year entry grades
default {}
}

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but i'm concerned that i'm thinking very "C" in my iteration loop for the array

To answer Anonymous monk,

To start with, i'd be very happy with an output that looks like below:

(subject)..|ABB|Maths|Physics|Design&Technology|Engineering

If i can get the progam to do this above, then i'll try and refine it to pull out specific grades

eg ([A-E]{1} in Design|design) returns the grade preceding that subject

Roboticus, thanks for that i may start with a defined array (there are ~200 A level possibilities, but they change very infrequently)and then develop it into one which adds subjects when detected once i get the hang of it.

You have also hit the nail on the head regarding the REGEXes, i was thinking about having a list produced of ones that the regex struggled with, or ones which didn't get any hits to see how i'm missing things too. I'd not thought about multiple passes however, nor repairing misspellings!

really appreciate the input i just need to plough through some text books and remind myself (or learn new things) appropriate to the task in hand

best wishes, Phil

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Re^3: CSV regex with hash/array program plan
by AnomalousMonk (Archbishop) on Nov 23, 2014 at 21:57 UTC
    when ((s/(\b[A-E]{3}\b)/XXX/g)) {@array[i,1] = $1}

    Capture groups don't work the same way in  s/// substitution versus  m// matching: 

    c:\@Work\Perl>perl -wMstrict -le
"my $s = 'xxx aBc yyy dE zzz';
 print qq{\$s: '$s'};
 ;;
 print qq{\$1: '$1'} if $s =~ s{ [AaBbCcDdEe]+ }{XXX}xmsg;
 print qq{\$s: '$s'};
"
$s: 'xxx aBc yyy dE zzz'
Use of uninitialized value $1 in concatenation (.) or string at -e lin
+e 1.
$1: ''
$s: 'xxx XXX yyy XXX zzz'

    [download]
    Capture groups work in a potentially surprising way in  s/// substitution and  m// matching: 
    c:\@Work\Perl>perl -wMstrict -le
"my $s = 'xxx aBc yyy dE zzz';
 print qq{\$s: '$s'};
 ;;
 print qq{\$1: '$1'} if $s =~ s{ ([AaBbCcDdEe]+) }{XXX}xmsg;
   print qq{\$s: '$s'};
  "
$s: 'xxx aBc yyy dE zzz'
$1: 'dE'
$s: 'xxx XXX yyy XXX zzz'

    [download]
    (note that only the last group matched is captured). Please see perlre, perlrequick, and perlretut.
    Also: I don't think  @array[i,1] = $1 is going to work the way you think it will whatever the value of  $1 may be (but I'm not sure just what you expect from this expression). Please see Slices in perldata. (Update: Something like this works for hashes: see  $; in perlvar. There's a more complete discussion of this old trick somewhere, but I can't locate it right now — anyone know where it is? (Update: Anonymonk informs me this is Multi-dimensional array emulation in perldata. This section was apparently added with Perl version 5.16.0 or 5.16.1. I only had 5.14 available locally and so missed it.))

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      Something like this works for hashes: see $; in perlvar. There's a more complete discussion of this old trick somewhere, but I can't locate it right now — anyone know where it is?
      It's in perldata... 'Multi-dimensional array emulation'.
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