interpolateList<T> function Value interpolation

List<Object?> Function(num) interpolateList<T>(List<T> a, List<T> b)

Returns an interpolator between the two lists a and b.

If b is a TypedData (e.g., Float64List), interpolateNumberList is called instead.

Internally, an list template is created that is the same length as b. For each element in b, if there exists a corresponding element in a, a generic interpolator is created for the two elements using interpolate. If there is no such element, the static value from b is used in the template. Then, for the given parameter t, the template’s embedded interpolators are evaluated. The updated list template is then returned.

For example, if a is the list [0, 1] and b is the list [1, 10, 100], then the result of the interpolator for t = 0.5 is the list [0.5, 5.5, 100].

Note: no defensive copy of the template list is created; modifications of the returned list may adversely affect subsequent evaluation of the interpolator. No copy is made for performance reasons; interpolators are often part of the inner loop of animated transitions.

Implementation

List<Object?> Function(num) interpolateList<T>(List<T> a, List<T> b) {
  if (b is TypedData) {
    return interpolateNumberList(a as List<num>, b as List<num>);
  }

  var nb = b.length,
      na = min(nb, a.length),
      l = b is List<num>
          ? interpolateNumber
          : b is List<String>
              ? interpolateColorOrString
              : b is List<Color>
                  ? interpolateRgb
                  : b is List<DateTime>
                      ? interpolateDate
                      : b is List<List>
                          ? interpolateList
                          : b is List<Map>
                              ? interpolateMap
                              : interpolate,
      x = List<Object? Function(num)>.generate(na, (i) => l(a[i], b[i])),
      c = List<Object?>.generate(nb, (i) => b[i]),
      i = 0;

  return (t) {
    for (i = 0; i < na; ++i) {
      c[i] = x[i](t);
    }
    return c;
  };
}