Question

A little intimidated by reject!, delete_if, select, keep_if, etc.

http://www.ruby-doc.org/core-1.9.3/Array.html#method-i-reject

What is the shortest way to modify an array deleting away elements that don’t match a condition in the {} block, while printing the count of those lost elements?

eg.

  puts "Filtered out #{(siglist.reject!{|r| r[:ret] < $retmin }).size} whose :ret < retmin(#{$retmin})"  

Seems to only print the number of surviving elements in the array after the reject.

Answer 1

Admittedly low-tech, but you could find the number of rejected values by the difference in length of the array before and after:

previous_length = siglist.size
puts "Filtered out #{previous_length - (siglist.reject!{|r| r[:ret] < $retmin }).size} whose :ret < retmin(#{$retmin})"