regex too longwinded and multiline issues - ruby

Question

im trying to change text to go from this:
\v 1 something \f + \xo footnote one \f* whatever \x + \xo footnote two \x* more text \f + \xo footnote three \f* blah blah blah \x + \xo footnote four \x*
\v 2 something \x + \xo footnote one \x*
to this:
\v 1 something \f * \xo footnote one \f* whatever \x ** \xo footnote two \x* more text \f *** \xo footnote three \f* blah blah blah \x $ \xo footnote four \x* \v 2 something \x * \xo footnote one \x*
so in each footnote, instead of a '+' each will have the next in the sequence (* ** *** $ $$ $$$ £) but the sequence has to reset when it gets to a new verse (\v) there can be up to 7 occurrences of footnotes between each verse.
i'm new to ruby so i know there's a better way to do this, what i've done is very long winded:
file = File.open('input.txt', 'r+')
contents = file.read
reassign = contents.gsub(/(\\v.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+/m, '\1*\3**\5***\7$\9$$')
.gsub(/(\\v.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+/m, '\1*\3**\5***\7$')
.gsub(/(\\v.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+/m, '\1*\3**\5***')
.gsub(/(\\v.*?(\\x|\\f) )\+(.*?(\\x|\\f) )\+/m, '\1*\3**')
.gsub(/(\\v.*?(\\x|\\f) )\+/m, '\1*')
new_file = File.open("output.txt", "w+")
new_file.write(reassign)
new_file.close
if i don't add the m after the regex search it skips a lot of footnotes longer than one line, but if i add it, it skips over the verses altogether and doesn't reset the sequence
Thanks

Answer 1

I suggest you first split('\v') the string, giving you an array of strings, map each of the strings in the resulting array to a string with the footnote symbols replaced with the appropriate strings, then join('\v') the strings back together.
Code
def map_footnote_symbols(str)
str.split('\v').map do |s|
t = %w{ * ** *** $ $$ $$$ £ }
s.gsub(/./) { |c| (c == '+') ? t.shift : c }
end.join('\v')
end
Example
str = "\v 1 something \f + \xo footnote one \f* whatever " +
"\x + \xo footnote two \x* more text \f + \xo footnote " +
"three \f* blah blah blah \x + \xo footnote four \x* \v 2 " +
"something \x + \xo footnote one \x*"
(I've broken the string into pieces so that in can be viewed without having to scroll horizontally.)
puts map_footnote_symbols str
#=> \v 1 something \f * \xo footnote one \f* whatever \x ** \xo |
# footnote two \x* more text \f *** \xo footnote three \f* |
# blah blah blah \x $ \xo footnote four \x* \v 2 something |
# \x * \xo footnote one \x*
(I've broken the output string into pieces so that in can be viewed without having to scroll horizontally. The character | indicates where I've broken each line.)
Explanation
a = str.split('\v')
#=> ["",
# " 1 something \\f + \\xo footnote one \\f* whatever \\x + \\xo |
# footnote two \\x* more text \\f + \\xo footnote three \\f* |
# blah blah blah \\x + \\xo footnote four \\x* ",
# " 2 something \\x + \\xo footnote one \\x*"]
(Again, I've broken the second string in the array into pieces so that in can be viewed without having to scroll horizontally.)
map passes each element of a into its block, assigning it to the block variable s. The first is:
s = ""
We then have:
t = %w{ * ** *** $ $$ $$$ £ }
#=> ["*", "**", "***", "$", "$$", "$$$", "£"]
b = "".gsub(/./) { |c| (c == '+') ? t.shift : c }
#=> ""
So "" is (obviously) mapped to "". The next element (string) map passes into the block is:
s = "footnote two \\x* more text \\f + \\xo footnote three \\f* " +
"blah blah blah \\x + \\xo footnote four \\x* "
The regex /./ causes gsub to pass each character of s to its block to determine the substituted value. (c == '+') is false for every character up to the first +, so these characters are all left unchanged (i.e., replaced by c). The first + is replaced by t.shift:
t = ["*", "**", "***", "$", "$$", "$$$", "£"]
t.shift #=> "*"
leaving
t #=> ["**", "***", "$", "$$", "$$$", "£"]
The characters up to the next + are left unchanged and that + is replaced by:
t.shift #=> "**"
leaving
t #=> ["***", "$", "$$", "$$$", "£"]
and so on. As a result:
c = a.map do |s|
t = %w{ * ** *** $ $$ $$$ £ }
s.gsub(/./) { |c| (c == '+') ? t.shift : c }
end
#=> ["",
# " 1 something \\f * \\xo footnote one \\f* whatever \\x ** \\xo |
# footnote two \\x* more text \\f *** \\xo footnote three \\f* |
# blah blah blah \\x $ \\xo footnote four \\x* ",
# " 2 something \\x * \\xo footnote one \\x*"]
All that remains is to reassemble the string:
c.join('\v')