Class for efficiently approximating expensive arithmetic operations. More...

#include <juce_LookupTable.h>

Public Member Functions
	LookupTable ()
	Creates an uninitialised LookupTable object.

	LookupTable (const std::function< FloatType(size_t)> &functionToApproximate, size_t numPointsToUse)
	Creates and initialises a LookupTable object.

void	initialise (const std::function< FloatType(size_t)> &functionToApproximate, size_t numPointsToUse)
	Initialises or changes the parameters of a LookupTable object.

FloatType	getUnchecked (FloatType index) const noexcept
	Calculates the approximated value for the given index without range checking.

FloatType	get (FloatType index) const noexcept
	Calculates the approximated value for the given index with range checking.

FloatType	operator[] (FloatType index) const noexcept

size_t	getNumPoints () const noexcept
	Returns the size of the LookupTable, i.e., the number of pre-calculated data points.

bool	isInitialised () const noexcept
	Returns true if the LookupTable is initialised and ready to be used.

Detailed Description

template<typename FloatType>
class dsp::LookupTable< FloatType >

Class for efficiently approximating expensive arithmetic operations.

The approximation is based on linear interpolation between pre-calculated values. The approximated function should be passed as a callable object to the constructor along with the number of data points to be pre-calculated. The accuracy of the approximation can be increased by using more points at the cost of a larger memory footprint.

Consider using LookupTableTransform as an easy-to-use alternative.

Example:

LookupTable<float> lut ([] (size_t i) { return std::sqrt ((float) i); }, 64);
auto outValue = lut[17];

See also: LookupTableTransform

Constructor & Destructor Documentation

◆ LookupTable() [1/2]

template<typename FloatType >

dsp::LookupTable< FloatType >::LookupTable ( )

Creates an uninitialised LookupTable object.

You need to call initialise() before using the object. Prefer using the non-default constructor instead.

See also: initialise

◆ LookupTable() [2/2]

template<typename FloatType >

dsp::LookupTable< FloatType >::LookupTable	(	const std::function< FloatType(size_t)> &	functionToApproximate,
		size_t	numPointsToUse )

Creates and initialises a LookupTable object.

Parameters

functionToApproximate	The function to be approximated. This should be a mapping from the integer range [0, numPointsToUse - 1].
numPointsToUse	The number of pre-calculated values stored.

Member Function Documentation

◆ initialise()

template<typename FloatType >

void dsp::LookupTable< FloatType >::initialise	(	const std::function< FloatType(size_t)> &	functionToApproximate,
		size_t	numPointsToUse )

Initialises or changes the parameters of a LookupTable object.

This function can be used to change what function is approximated by an already constructed LookupTable along with the number of data points used. If the function to be approximated won't ever change, prefer using the non-default constructor.

Parameters

functionToApproximate	The function to be approximated. This should be a mapping from the integer range [0, numPointsToUse - 1].
numPointsToUse	The number of pre-calculated values stored.