1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
|
// Copyright 2015, Tobias Hermann and the FunctionalPlus contributors.
// https://github.com/Dobiasd/FunctionalPlus
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#pragma once
#include <fplus/container_common.hpp>
#include <fplus/maybe.hpp>
#include <cmath>
namespace fplus
{
// API search type: elem_at_float_idx : (Float, [a]) -> a
// fwd bind count: 1
// Interpolates linearly between elements.
// xs must be non-empty.
template <typename Container,
typename T = typename Container::value_type>
T elem_at_float_idx(double idx, const Container& xs)
{
assert(is_not_empty(xs));
if (idx <= 0.0)
{
return xs.front();
}
std::size_t idx_floor = static_cast<std::size_t>(floor(idx));
std::size_t idx_ceil = static_cast<std::size_t>(ceil(idx));
if (idx_ceil >= size_of_cont(xs))
{
return xs.back();
}
double idx_floor_float = static_cast<double>(idx_floor);
double idx_ceil_float = static_cast<double>(idx_ceil);
double weight_floor = idx_ceil_float - idx;
double weight_ceil = idx - idx_floor_float;
return
(weight_floor * elem_at_idx(idx_floor, xs) +
weight_ceil * elem_at_idx(idx_ceil, xs));
}
} // namespace fplus
|
