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### Re: Finding gaps in date ranges

 on May 11, 2001 at 01:11 UTC ( #79568=note: print w/replies, xml ) Need Help??

in reply to Finding gaps in date ranges

I'm a big fan of peanos axioms. So I started with the idea: if it weren't dates we were dealing with, but natural numbers, then I would just sort the numbers, and compute the gaps with one simple loop.

I decided to convert you date-format to something that can be sorted numerically (YYYYMM, with month in two digits, like "02"), and I made up a function "nextmonth" for incrementing the date.

sub nextmonth { my(\$year, \$month); \$year = substr(\$_[0], 0, 4); \$month = substr(\$_[0], 4, 2); \$month++; while (\$month > 12) { \$year++; \$month-=12; } return \$year . sprintf("%02d", \$month); } sub find_gaps { my \$dates = shift; my(@missing, @keys, \$last); # convert your date-format to mine @keys = map { s/-(.)\$/0\$1/; s/-//; \$_ } keys %\$dates; # my format can be sorted numerically @keys = sort @keys; # in the loop we need two variables: # \$last for the date before the current one, # and \$date for the current date \$last = shift(@keys); foreach my \$date ( @keys ) { while (1) { \$last = nextmonth(\$last); last if \$last eq \$date; push(@missing, \$last); } \$last = \$date; } # convert my date-format back to yours @missing = map { s/0(.)\$/\$1/; s/^(....)/\$1-/; \$_ } @missing; return \@missing; }

share and enjoy

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Re: Re: Finding gaps in date ranges
by bjelli (Pilgrim) on May 11, 2001 at 01:15 UTC

boohoo, the above article is mine, but I posted it anonymously by mistake. oh higher powers, if it please you, transfer the XPs of the article to this humble scribe.

I'm a big fan of peanos axioms. So I started with the idea: if it weren't dates we were dealing with, but natural numbers, then I would just sort the numbers, and compute the gaps with one simple loop. I decided to convert you date-format to something that can be sorted numerically (YYYYMM, with month in two digits, like "02"), and I made up a function "nextmonth" for incrementing the date.

sub nextmonth { my(\$year, \$month); \$year = substr(\$_[0], 0, 4); \$month = substr(\$_[0], 4, 2); \$month++; while (\$month > 12) { \$year++; \$month-=12; } return \$year . sprintf("%02d", \$month); } sub find_gaps { my \$dates = shift; my(@missing, @keys, \$last); # convert your date-format to mine @keys = map { s/-(.)\$/0\$1/; s/-//; \$_ } keys %\$dates; # my format can be sorted numerically @keys = sort @keys; # in the loop we need two variables: # \$last for the date before the current one, # and \$date for the current date \$last = shift(@keys); foreach my \$date ( @keys ) { while (1) { \$last = nextmonth(\$last); last if \$last eq \$date; push(@missing, \$last); } \$last = \$date; } # convert my date-format back to yours @missing = map { s/0(.)\$/\$1/; s/^(....)/\$1-/; \$_ } @missing; return \@missing; }

share and enjoy

--
Brigitte    'I never met a chocolate I didnt like'    Jellinek
http://www.horus.com/~bjelli/         http://perlwelt.horus.at

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