I'm trying to isolate certain strings in an array, e.g.,
["banana man", "apple", "banana woman"]
which are identifiable by the start of the string (i.e. substring). I want to keep 'banana man' and 'banana woman' but remove 'apple'. Any help would be appreciated.
This is a great usecase for grep
ary = ["banana man", "apple", "banana woman"]
ary.grep(/^banana/) # => ["banana man", "banana woman"]
grep results in a visually simple expression, the benchmark shows it's costly.Try start_with? and select to choose just those that start with the string you want:
["banana man", "apple", "banana woman"].select { |i| i.start_with?("bana") }
=> ["banana man", "banana woman"]
Benchmark time:
require 'fruity'
ARY = ["banana man", "apple", "banana woman"]
ARY.grep(/^banana/) # => ["banana man", "banana woman"]
ARY.select { |i| i.start_with?("bana") } # => ["banana man", "banana woman"]
compare do
grep_only { ARY.grep(/^banana/) }
select_start_with { ARY.select { |i| i.start_with?("bana") } }
end
# >> Running each test 4096 times. Test will take about 1 second.
# >> select_start_with is faster than grep_only by 3x ± 1.0
Extending ARY:
ARY = ["banana man", "apple", "banana woman"] * 1000
compare do
grep_only { ARY.grep(/^banana/) }
select_start_with { ARY.select { |i| i.start_with?("bana") } }
end
# >> Running each test 8 times. Test will take about 1 second.
# >> select_start_with is faster than grep_only by 3x ± 0.1
At the Tin Mans behest, and due to the fact that your actual specifications are very vague, I will add this alternative solution as a possible but potentially error prone option.
ARY = ["banana man", "apple", "banana woman"]
ARY.join(' ').scan(/banana\s\w+/)
#=> ["banana man", "banana woman"]
This will out perform grep but is about half the speed of select and start_with? combination and is based solely on the post and not your potentially underlying intentions.
"banana") in advance or do you have to extract / identify it from the given strings?"apple"isolated from the other two elements? Is it because it starts with"a"?ais your array and we interpret your question literally (as we should),a.delete("apple")is sufficient (though I doubt that's what you are looking for).