Lookaround Enumerable

When working with time series, it is common to perform operations that depend on a sliding window of values. Lookaround Enumerable adds two main methods, and several sub-helpers to assist with running map/collect, reduce/inject, and find_all/select queries that depend on the previous values (Enumerable#each_with_prev), or a whole window of values (Enumerable#each_with_window). This gem contains these methods as refinements.

Add this line to your application's Gemfile:

gem 'lookaround-enumerable'

And then execute:

$ bundle

Or install it yourself as:

$ gem install lookaround-enumerable

require 'lookaround-enumerable'
using LookaroundEnum

The LookaroundEnum contains the refinements, so they can be targeted to selected areas of code.

# Maps characters after a capital letter to "x"
"AbCdefgHiJKl".each_char.map_with_prev(1, filler: "a") {|x, previous| previous.upcase == previous ? "x" : x}.join
# => "AxCxefgHxJxx"

# select characters surrounded by > <, ignoring the bounds (crop)
"Ab>c<defg>h<i>j<kLm>n<op".each_char.select_with_window(-1..1, crop: true) { |left, item, right| left + right == "><" }.join
# => "cjhn"

• Set what beyond the Enumerable is with filler:
• Ignore all iterations that look beyond the Enumerable with crop: true
• Remove extra details from chains with trim: true

See the documentation spec tests under spec/ for more examples.

That's a tricky question. By default, single left/right views should just work, but you might have to play with the expand parameter or do a p *args to figure out more advanced usage, like chaining with memos or objects. The each_with_prev family does |(*this), ((*previous1), ..., (*previous_n))| with older/lower indexes to the right. The each_with_window family does |((*previous_n), ..., (*previous1)), (*this), ((*next1), ..., (*next_n))| with older/lower indexes on the left.

After checking out the repo, run bundle install to install dependencies. Then, run rake spec or rspec to run the tests.

Bug reports and pull requests are welcome on GitHub at https://github.com/byteit101/lookaround-enumerable.