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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
part of dart.ui;
/// Linearly interpolate between two numbers, `a` and `b`, by an extrapolation
/// factor `t`.
///
/// When `a` and `b` are equal or both NaN, `a` is returned. Otherwise,
/// `a`, `b`, and `t` are required to be finite or null, and the result of `a +
/// (b - a) * t` is returned, where nulls are defaulted to 0.0.
double? lerpDouble(num? a, num? b, double t) {
if (a == b || (a?.isNaN ?? false) && (b?.isNaN ?? false)) {
return a?.toDouble();
}
a ??= 0.0;
b ??= 0.0;
assert(a.isFinite, 'Cannot interpolate between finite and non-finite values');
assert(b.isFinite, 'Cannot interpolate between finite and non-finite values');
assert(t.isFinite, 't must be finite when interpolating between values');
return a * (1.0 - t) + b * t;
}
/// Linearly interpolate between two doubles.
///
/// Same as [lerpDouble] but specialized for non-null `double` type.
double _lerpDouble(double a, double b, double t) {
return a * (1.0 - t) + b * t;
}
/// Linearly interpolate between two integers.
///
/// Same as [lerpDouble] but specialized for non-null `int` type.
double _lerpInt(int a, int b, double t) {
return a + (b - a) * t;
}
/// Same as [num.clamp] but specialized for non-null [int].
int _clampInt(int value, int min, int max) {
assert(min <= max);
if (value < min) {
return min;
} else if (value > max) {
return max;
} else {
return value;
}
}