Download - The Bastards Book of Regular Expressions

Capture, Reuse 86ApplesOraclesOrangesOreThe most important letter is the left-most one: A comes before O in the alphabet, so all words thatbegin with A will come before any word that starts with O. But what if the words start with the sameletter? Then you compare the second letters, and so forth.This is the same with dates. In the American human-readable format, 03-09-2001 would comebefore 05-22-1978, as 03 comes earlier in the numerical scale than does 05. But chronologically, ofcourse, 05-22-1978 is several decades before 03-09-2001. In the programmer-friendly version, the“biggest” parts of the date come first, i.e. the year, then the month and day. This makes sorting easy,because the alphabetical-order of the date text is the same as the chronological order of the actualdates.So, given the human readable version of the dates, write a regex that converts them to theprogrammer friendly version.AnswerFind (\d+)-(\d+)-(\d+)Replace $3-$1-$2Exercise: Zero-pad the datesThe above exercise isn’t completely realistic, however, because the human-readable dates are usuallywritten in a more shorthand way:3-9-200111-14-20125-22-1978The month of March, in other words, is written simply as 3, not as 03Why is that extra zero there? If you think of the computer-sortable scenario, those extra zeros arevital. Consider the issue of two dates with the same year. In human readable format:11-20-20023-20-2002In machine-readable format: