partialRatio function

double partialRatio(String a, String b)

fuzzywuzzy-style partial ratio: how well the shorter string matches the best-aligning slice of the longer one, in [0, 1].

Slides a window the length of the shorter string across the longer string and returns the best LevenshteinUtils.ratio of any window. This scores a substring match high even when the surrounding text differs — e.g. 'New York' against 'New York City' — where the plain whole-string ratio would be penalized for the extra words. Comparison is case-insensitive.

Two empty strings score 1.0; one empty against a non-empty scores 0.0. Audited: 2026-06-12 11:26 EDT

Implementation

double partialRatio(String a, String b) {
  final String shorter = (a.length <= b.length ? a : b).toLowerCase();
  final String longer = (a.length <= b.length ? b : a).toLowerCase();

  if (shorter.isEmpty) {
    return longer.isEmpty ? 1.0 : 0.0;
  }

  double best = 0.0;
  // Each window is the shorter string's length; the best-aligned slice wins.
  for (int start = 0; start + shorter.length <= longer.length; start++) {
    final double r = LevenshteinUtils.ratio(
      shorter,
      longer.substring(start, start + shorter.length),
    );
    if (r > best) {
      best = r;
    }
  }

  return best;
}