What is the difference between collect,select, reject and inject in ruby?

What is the difference between collect,select, reject and inject in ruby?

     Some of the most commonly used Enumerable  iterators are the rhyming methods collect , select , reject , and inject .

       The collect  method (also known as map ) executes  its associated block for each element of the enumerable object, and collects the return values of the blocks into an array:

                 squares = [1,2,3].collect {|x| x*x} # => [1,4,9]

        The select  method invokes the associated block for each element in the enumerable

object, and returns an array of elements for which the block returns a value other than false  or nil . For example:

                 evens = (1..10).select {|x| x%2 == 0} # => [2,4,6,8,10]

        The reject  method is simply the opposite of select ; it returns an array of elements for

which the block returns nil  or false . For example:

                odds = (1..10).reject {|x| x%2 == 0} # => [1,3,5,7,9]

          The inject  method is a little more complicated than the others. It invokes the associated

block with two arguments. The first argument is an accumulated value of some sort from previous iterations. The second argument is the next element of the enumerable object. The return value of the block becomes the first block argument for the next iteration, or becomes the return value of the iterator after the last iteration.

          data = [2, 5, 3, 4]

          sum = data.inject {|sum, x| sum + x } # => 14 (2+5+3+4)

          floatprod = data.inject(1.0) {|p,x| p*x } # => 120.0 (1.0*2*5*3*4)

          max = data.inject {|m,x| m>x ? m : x } # => 5 (largest element)