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juce::dsp::LookupTable< FloatType > Class Template Reference

#include <juce_LookupTable.h>

Public Member Functions

 LookupTable ()
 
 LookupTable (const std::function< FloatType(size_t)> &functionToApproximate, size_t numPointsToUse)
 
void initialise (const std::function< FloatType(size_t)> &functionToApproximate, size_t numPointsToUse)
 
FloatType getUnchecked (FloatType index) const noexcept
 
FloatType get (FloatType index) const noexcept
 
FloatType operator[] (FloatType index) const noexcept
 
size_t getNumPoints () const noexcept
 
bool isInitialised () const noexcept
 

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

Definition at line 53 of file juce_LookupTable.h.

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

Definition at line 33 of file juce_LookupTable.cpp.

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

Definition at line 39 of file juce_LookupTable.cpp.

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
indexThe approximation is calculated for this non-integer index.
Returns
The approximated value at the given index.
See also
getUnchecked, operator[]

Definition at line 124 of file juce_LookupTable.h.

◆ 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.

Definition at line 139 of file juce_LookupTable.h.

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

◆ 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
indexThe approximation is calculated for this non-integer index.
Returns
The approximated value at the given index.
See also
get, operator[]

Definition at line 96 of file juce_LookupTable.h.

Referenced by juce::dsp::LookupTable< FloatType >::get(), and juce::dsp::LookupTable< FloatType >::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
functionToApproximateThe function to be approximated. This should be a mapping from the integer range [0, numPointsToUse - 1].
numPointsToUseThe number of pre-calculated values stored.

Definition at line 47 of file juce_LookupTable.cpp.

◆ isInitialised()

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

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

Definition at line 142 of file juce_LookupTable.h.

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

◆ operator[]()

template<typename FloatType >
FloatType juce::dsp::LookupTable< FloatType >::operator[] ( FloatType  index) const
inlinenoexcept
See also
getUnchecked

Definition at line 136 of file juce_LookupTable.h.


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