提供两个英文单词，要求计算它们的编辑距离，并输出。
horse, ros
The edit distance between "horse" and "ros" is 3. 

The steps to transform "horse" to "ros" are:

1. Replace "h" with "r" ( "h" -> "r" )
2. Delete "o" ( "or" -> "r" )
3. Delete "e" ( "rse" -> "rs" )
4. Replace "s" with "o" ( "rs" -> "ro" )