How to do it the Ruby way : Count no. of occurence of a in b

Question

This is the snippet of code i'm using now:

def countOccurences(a, b)
  #counts the number of occurences of a in b 
  count=0
  cur=0
  while cur < b.length do
    temp=b.index(a, cur)
    if temp == nil
      break
    end
    count=count+1
    cur=temp+a.length
  end
  return count
end

Is there any Ruby function that does this? Any functional equivalent? Or anything better?

Answer 1

The most obvious way

enum.find_all {| obj | block } => array

plus

array.length

or you could just do it with a fold

enum.inject {| memo, obj | block } => obj

Answer 2

I'm assuming b is an array and b is an object to look for in the array.

ary = ["foo", "bar", "baz", "foo", "foo", "maz"]
look_for = "foo"

p a.detect {|i| i == look_for }.length
# => 3

You could also monkey-patch this into Array.

class Array
  def occurrences_of(object)
    detect {|i| i == object }.length
  end
end

p ["foo", "bar", "baz", "foo", "foo", "maz"].occurrences_of("foo")
# => 3

Answer 3

You just need to loop through the array using each, and through that create an array with the key of "a" and count as a value. Then just return the count.

def count_occurences(a, b)
  r = Array.new
  b.eachdo |e|
    if e == a 
      r[e]++
    end
  end
end

That should do it!

Answer 4

If a and b are strings:

b.scan(a).length