Hi everyone, I hope it’s appropriate to post this question here. I
couldn’t find anywhere else to post it (posting to the Ruby group
didn’t work). I’m trying to write a regular expression to turn this
string:
‘johnny went to the [shops] and played [games,soccer,foot ball] with
others.’
into this:
[‘johnny went to the’, [‘shops’], ‘and played’, [‘games’, ‘soccer’,
‘foot ball’], ‘with others.’]
Key features are that white space needs to be stripped from around the
snippets, and I need to be able to determine which parts are just
normal text and which parts are to be used as gaps where people fill
in the missing info. If you haven’t already figured it out, this is
for a children’s quiz engine. When a phrase appears in square brackets
it’s a blank, the system will display a text box for the user to type
into. If there are multiple items in the square brackets seperated by
comma’s (and optional spaces around the comma’s by lazy users) then
the system will display the choices in a random order in a drop down
box (the first choice in the list is the correct one).
I’ve had a long go at it myself but I just don’t fully grasp the
regexp language:
irb(main):027:0> ‘johnny went to the [shops] and played
[games,soccer,foot ball]
with others.’.split(/[(?:([(?:\s)\w(?:\s)]+)(?:,([(?:\s)\w(?:\s)]
+))*)]/)
=> ["johnny went to the ", “shops”, " and played “, “games”, “foot
ball”, " with
others.”]
I’ve tried doing groupings but it seems to make things worse
This is kinda ghetto (particularly needing to check chunk.length) but it
works on your sample string.
def parse_item(lin)
ret = Array.new
re = Regexp.new(/([^[]]+?([|]))+?/)
lin.split(re).each do |chunk|
if chunk.length > 1 then
case chunk
when /]$/
# bracketed option list
ret << chunk[0…-2].split(’,’)
else
# plain chunk of text
ret << chunk.gsub(/[$/, ‘’).strip
end
end
end
ret.inspect
end
scanner = StringScanner.new(correct_answers)
# last position the scanner was in
last_pos = 0
output = []
while scanner.scan_until(/\[(.+?)\]/) # non-greedy matching so we
only swallow the first bracket
# scanner[0] contains the string matched by the regexp
# scanner[1] contains the value surrounded the parantheses in
the regexp
# current position is right up to bracketed text
current_pos = scanner.pos - 1 - scanner[0].length
# the 'chunk' is the text from the last position the scanner
stopped at
# up to the current position
chunk = scanner.string[last_pos .. current_pos]
output << chunk unless chunk.empty?
# store the position the scanner is at for next time round the
loop
last_pos = scanner.pos
# extract the question answer thingies
answers = scanner[1].split(',') # returns array
# strip whitespace around each possible answer
answers.each {|v| v.strip! } # works because strip! is
destructive
# add answers array
output << answers
end
# make sure we have any text after the last question/answer
last_chunk = scanner.string[last_pos..-1]
output << last_chunk unless last_chunk.empty?
output
end
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