Mesomorphic have produced a series of guides on home working, we’re reproduced in full here with permission, 但是我强烈建议你 访问他们的网站 for the most up to date information
Charlotte hasn’t been able to get to the gym recently, as she’s stuck at home due to the coronavirus lockdown. She’s having to get by with doing a lot of push-ups, and has been keeping a careful record of how many push-ups she manages to do each day. Each day’s total has been added to a Ruby array:
daily_push_up_totals = [10, 15, 25, 27, 30, 50, 55, 55, 60, 62, 62, 65, 65, 66]
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Charlotte would like to know two things: the total number of push-ups she’s done each week, and her greatest improvement from one day to the next.
To calculate the total of number of push-up Charlotte has done each week, one approach would be to use each_slice. This Array method divides the array into sections (or slices) and passes each section to the block. The number of values in each section is passed in as a parameter. 举个例子:
daily_push_up_totals.each_slice (7) { |week_totals| print weekly_totals }
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会导致:
[10, 15, 25, 27, 30, 50, 55][55, 60, 62, 62, 65, 65, 66]
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We’ve managed to divide up the array into slices of seven values each, so all we need to do obtain the weekly totals is to add up each slice using 总和:
daily_push_up_totals.each_slice (7) { |week_totals| puts "Weekly total: #{week_totals.总和}}
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导致:
每周总数:212
每周总数:445
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We can make the output more useful by using with_index:
daily_push_up_totals.each_slice (7).with_index(1) { |week_totals, week_number| puts "Total for week #{week_number}: #{week_totals.总和}}
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这将给我们:
Total for week 1: 212
Total for week 2: 445
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So how can we figure out Charlotte’s greatest day-on-day improvement? 让我们试着使用 each_cons. This Array method supplies the given block with n consecutive elements, starting from each element in turn. 困惑? An example should make things clearer:
daily_push_up_totals.each_cons (2){ |values| print values }
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将返回:
[10, 15][15, 25][25, 27][27, 30]...
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等等.......
鉴于这种, calculating the greatest day-on-day improvement is a case of finding the differences between each of these pairs of daily totals, and finding the 马克斯imum:
daily_push_up_totals.each_cons (2).map{ |day1, day2| day2 - day1 }.马克斯
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返回:
20
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We’re done – Charlotte will now be able to keep track of her progress no matter how long the lockdown lasts.
多亏了 亚当·L. 沃森 for spotting an error in a previous version of this post.
I’d love to hear your thoughts on each_slice, each_cons, the uses you’ve found for them, and indeed, exercising during lockdown. Why not leave a comment below?