std::lerp
Defined in header <cmath>
|
||
| (1) | ||
|
constexpr
float lerp(
float a, float b, float t )
noexcept
;
constexpr
double lerp(
double a, double b, double t )
noexcept
;
|
(since C++20) (until C++23) |
|
|
constexpr
/* floating-point-type */
lerp( /* floating-point-type */ a, |
(since C++23) | |
Defined in header <cmath>
|
||
|
template
<
class Arithmetic1, class Arithmetic2, class Arithmetic3 >
constexpr /* common-floating-point-type */ |
(A) | (since C++20) |
[
0
,
1
)
(the linear extrapolation otherwise), i.e. the result of
a+t(b−a) with accounting for floating-point calculation imprecision.
The library provides overloads for all cv-unqualified floating-point types as the type of the parameters a, b and t
(since C++23)
Parameters
| a, b, t | - | floating-point or integer values |
Return value
a + t(b − a)
When std::isfinite (a) && std::isfinite (b) is true
- If t == 0, the result is equal to a.
- If t == 1, the result is equal to b.
- If t >= 0 && t <= 1
- If std::isfinite (t) && a == , the result is equal to a
- If std::isfinite (t) || (b - a ! = 0 && std::isinf (t) ) , the result is not NaN
Let CMP(x, y) be 1 if x > y, -1 if x < y, and 0 otherwise. For any t1 and t2
- CMP(std:: lerp (a, b, t2), std:: lerp (a, b, t1) )
- CMP(t2, t1), and
- CMP(b, a)
is non-negative. (That is, std::lerp is monotonic.)
Notes
The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their first argument num1, second argument num2 and third argument num3
|
(until C++23) |
|
If num1, num2 and num3 have arithmetic types, then std::lerp(num1, num2, num3) has the same effect as
std::
lerp
(
static_cast
<
/*common-floating-point-type*/
>
(num1)
If no such floating-point type with the greatest rank and subrank exists, then overload resolution |
(since C++23) |
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_interpolate |
201902L |
(C++20) | std::lerp, std::midpoint
|
Example
#include <cassert> #include <cmath> #include <iostream> float naive_lerp(float a, float b, float t) { return a + t * (b - a); } int main() { std::cout << std::boolalpha; const float a = 1e8f, b = 1.0f; const float midpoint = std::lerp(a, b, 0.5f); std::cout << "a = " << a << ", " << "b = " << b << '\n' << "midpoint = " << midpoint << '\n'; std::cout << "std::lerp is exact: " << (a == std::lerp(a, b, 0.0f)) << ' ' << (b == std::lerp(a, b, 1.0f)) << '\n'; std::cout << "naive_lerp is exact: " << (a == naive_lerp(a, b, 0.0f)) << ' ' << (b == naive_lerp(a, b, 1.0f)) << '\n'; std::cout << "std::lerp(a, b, 1.0f) = " << std::lerp(a, b, 1.0f) << '\n' << "naive_lerp(a, b, 1.0f) = " << naive_lerp(a, b, 1.0f) << '\n'; assert(not std::isnan(std::lerp(a, b, INFINITY))); // lerp here can be -inf std::cout << "Extrapolation demo, given std::lerp(5, 10, t):\n"; for (auto t{-2.0}; t <= 2.0; t += 0.5) std::cout << std::lerp(5.0, 10.0, t) << ' '; std::cout << '\n'; }
Possible output:
a = 1e+08, b = 1 midpoint = 5e+07 std::lerp is exact?: true true naive_lerp is exact?: true false std::lerp(a, b, 1.0f) = 1 naive_lerp(a, b, 1.0f) = 0 Extrapolation demo, given std::lerp(5, 10, t): -5 -2.5 0 2.5 5 7.5 10 12.5 15
See also
|
(C++20)
|
midpoint between two numbers or pointers (function template) |