Constructor.

Computes diff between sequences of strings.

This can be used to compute things like case-insensitve diffs, or diffs which ignore changes in white-space.

• $from_lines $from_lines: array An array of strings. (Typically these are lines from a file.)
• $to_lines $to_lines: array An array of strings.
• $mapped_from_lines $mapped_from_lines: array This array should have the same size number of elements as $from_lines. The elements in $mapped_from_lines and $mapped_to_lines are what is actually compared when computing the diff.
• $mapped_to_lines $mapped_to_lines: array This array should have the same number of elements as $to_lines.