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

#include <juce_LookupTable.h>

Inheritance diagram for juce::dsp::LookupTable< FloatType >:

Collaboration diagram for juce::dsp::LookupTable< FloatType >:

[legend]

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

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

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

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

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

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

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

FloatType	operator[] (FloatType index) const noexcept

Private Member Functions
size_t	getGuardIndex () const noexcept

void	prepare () noexcept

Static Private Member Functions
static size_t	getRequiredBufferSize (size_t numPointsToUse) noexcept

Private Attributes
Array< FloatType >	data

Detailed Description

template<typename FloatType>
class juce::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

@tags{DSP}

Constructor & Destructor Documentation

◆ LookupTable() [1/2]

template<typename FloatType >

juce::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 >

juce::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

◆ get()

template<typename FloatType >

FloatType juce::dsp::LookupTable< FloatType >::get ( FloatType index ) const

inlinenoexcept

Calculates the approximated value for the given index with range checking.

This can be called with any input indices. If the provided index is out-of-range either the bottom or the top element of the LookupTable is returned.

If the index is guaranteed to be in range use the faster getUnchecked() instead.

Parameters

index The approximation is calculated for this non-integer index.

Returns: The approximated value at the given index.

See also: getUnchecked, operator[]

◆ getGuardIndex()

template<typename FloatType >

size_t juce::dsp::LookupTable< FloatType >::getGuardIndex ( ) const

inlineprivatenoexcept

Referenced by juce::dsp::LookupTable< NumericType >::get().

◆ getNumPoints()

template<typename FloatType >

size_t juce::dsp::LookupTable< FloatType >::getNumPoints ( ) const

inlinenoexcept

Returns the size of the LookupTable, i.e., the number of pre-calculated data points.

Referenced by juce::dsp::LookupTable< NumericType >::get(), juce::dsp::LookupTable< NumericType >::getGuardIndex(), and juce::dsp::LookupTable< NumericType >::getUnchecked().

◆ getRequiredBufferSize()

template<typename FloatType >

static size_t juce::dsp::LookupTable< FloatType >::getRequiredBufferSize ( size_t numPointsToUse )

inlinestaticprivatenoexcept

Referenced by juce::dsp::LookupTable< NumericType >::getGuardIndex().

◆ getUnchecked()

template<typename FloatType >

FloatType juce::dsp::LookupTable< FloatType >::getUnchecked ( FloatType index ) const

inlinenoexcept

Calculates the approximated value for the given index without range checking.

Use this if you can guarantee that the index is non-negative and less than numPoints. Otherwise use get().

Parameters

index The approximation is calculated for this non-integer index.

Returns: The approximated value at the given index.

See also: get, operator[]

Referenced by juce::dsp::LookupTable< NumericType >::get(), and juce::dsp::LookupTable< NumericType >::operator[]().

◆ initialise()

template<typename FloatType >

void juce::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.

◆ isInitialised()

template<typename FloatType >

bool juce::dsp::LookupTable< FloatType >::isInitialised ( ) const

inlinenoexcept

Returns true if the LookupTable is initialised and ready to be used.

Referenced by juce::dsp::LookupTable< NumericType >::getUnchecked().

◆ operator[]()

template<typename FloatType >

FloatType juce::dsp::LookupTable< FloatType >::operator[] ( FloatType index ) const

inlinenoexcept

See also: getUnchecked

◆ prepare()

template<typename FloatType >

void juce::dsp::LookupTable< FloatType >::prepare ( )

privatenoexcept

Member Data Documentation

◆ data

template<typename FloatType >

Array<FloatType> juce::dsp::LookupTable< FloatType >::data

private

Referenced by juce::dsp::LookupTable< NumericType >::getNumPoints(), juce::dsp::LookupTable< NumericType >::getUnchecked(), and juce::dsp::LookupTable< NumericType >::isInitialised().

The documentation for this class was generated from the following file:

juce_LookupTable.h

Public Member Functions

Private Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

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

Constructor & Destructor Documentation

◆ LookupTable() [1/2]

◆ LookupTable() [2/2]

Member Function Documentation

◆ get()

◆ getGuardIndex()

◆ getNumPoints()

◆ getRequiredBufferSize()

◆ getUnchecked()

◆ initialise()

◆ isInitialised()

◆ operator[]()

◆ prepare()

Member Data Documentation

◆ data

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