CODEWITHSUNDEEP
c++templatesiterator
tderensis
tderensis

Reputation: 90

How to write a templated function that uses iterators and specific types

I'm trying to write a function which can receive an iterator of std::pair (points along a curve) which can do linear interpolation for a given X and return Y.

A function signature similar to this would be great, but I can't figure out how to set up the template definition.

template<class RandomAccessIterator, typename X, typename Y >
Y piecewiseLinearInterpolate(
    RandomAccessIterator begin, 
    RandomAccessIterator end,
    X x);

However, doing this results in template argument deduction/substitution failing.

This also fails to compile:

template<class RandomAccessIterator, template <class X, class Y> class std::pair >
constexpr Y piecewiseLinearInterpolate(
    RandomAccessIterator begin,
    RandomAccessIterator end,
    X x);

I have gotten a function with the following function signature to work, but it requires me to specify the types contained in the pair.

using AdcCount16 = uint16_t;
using Pressure = int;

template<class RandomAccessIterator>
Pressure piecewiseLinearInterpolate(
    RandomAccessIterator begin,
    RandomAccessIterator end,
    AdcCount16 x);

How can I write a generalized function which can receive a random access iterator of std::pair and a value of type X which returns a value of type Y?

Edit:

I am calling the function like this:

using PressurePoint = std::pair<AdcCount16, Pressure>;

PressurePoint piecewise[] = {
    {0, 1},
    {2, 3},
    {5, 9}
};

Pressure p1 = piecewiseLinearInterpolate(
    std::cbegin(piecewise),
    std::cend(piecewise),
    3);

assert(p1 == 5);

Upvotes: 1

Views: 84

Answers (1)

n. m. could be an AI
n. m. could be an AI

Reputation: 119847

You want something like this

template<class RandomAccessIterator>
auto piecewiseLinearInterpolate(
    RandomAccessIterator begin, 
    RandomAccessIterator end,
    decltype(begin->first)) -> 
               decltype(begin->second);

Upvotes: 3

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