26 Numerics library [numerics]

26.8 Mathematical functions for floating-point types [c.math]

26.8.4 Linear interpolation [c.math.lerp]

constexpr float lerp(float a, float b, float t); constexpr double lerp(double a, double b, double t); constexpr long double lerp(long double a, long double b, long double t);
Returns: .
Remarks: Let r be the value returned.
If isfinite(a) && isfinite(b), then:
  • If t == 0, then r == a.
  • If t == 1, then r == b.
  • If t >= 0 && t <= 1, then isfinite(r).
  • If isfinite(t) && a == b, then r == a.
  • If isfinite(t) || !isnan(t) && b-a != 0, then !isnan(r).
Let CMP(x,y) be 1 if x > y, -1 if x < y, and 0 otherwise.
For any t1 and t2, the product of CMP(lerp(a, b, t2), lerp(a, b, t1)), CMP(t2, t1), and CMP(b, a) is non-negative.