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juce::Expression Class Reference

#include <juce_Expression.h>

Classes

class  Scope
 
struct  Symbol
 

Public Types

enum  Type { constantType , functionType , operatorType , symbolType }
 

Public Member Functions

 Expression ()
 
 ~Expression ()
 
 Expression (const Expression &)
 
Expressionoperator= (const Expression &)
 
 Expression (Expression &&) noexcept
 
Expressionoperator= (Expression &&) noexcept
 
 Expression (double constant)
 
 Expression (const String &stringToParse, String &parseError)
 
String toString () const
 
Expression operator+ (const Expression &) const
 
Expression operator- (const Expression &) const
 
Expression operator* (const Expression &) const
 
Expression operator/ (const Expression &) const
 
Expression operator- () const
 
double evaluate () const
 
double evaluate (const Scope &scope) const
 
double evaluate (const Scope &scope, String &evaluationError) const
 
Expression adjustedToGiveNewResult (double targetValue, const Scope &scope) const
 
Expression withRenamedSymbol (const Symbol &oldSymbol, const String &newName, const Scope &scope) const
 
bool referencesSymbol (const Symbol &symbol, const Scope &scope) const
 
bool usesAnySymbols () const
 
void findReferencedSymbols (Array< Symbol > &results, const Scope &scope) const
 
Type getType () const noexcept
 
String getSymbolOrFunction () const
 
int getNumInputs () const
 
Expression getInput (int index) const
 

Static Public Member Functions

static Expression symbol (const String &symbol)
 
static Expression function (const String &functionName, const Array< Expression > &parameters)
 
static Expression parse (String::CharPointerType &stringToParse, String &parseError)
 

Detailed Description

A class for dynamically evaluating simple numeric expressions.

This class can parse a simple C-style string expression involving floating point numbers, named symbols and functions. The basic arithmetic operations of +, -, *, / are supported, as well as parentheses, and any alphanumeric identifiers are assumed to be named symbols which will be resolved when the expression is evaluated.

Expressions which use identifiers and functions require a subclass of Expression::Scope to be supplied when evaluating them, and this object is expected to be able to resolve the symbol names and perform the functions that are used.

Definition at line 43 of file juce_Expression.h.

Member Enumeration Documentation

◆ Type

Constructor & Destructor Documentation

◆ Expression() [1/5]

juce::Expression::Expression ( )

Creates a simple expression with a value of 0.

Definition at line 923 of file juce_Expression.cpp.

Referenced by adjustedToGiveNewResult(), function(), getInput(), juce::Expression::Scope::getSymbolValue(), operator*(), operator+(), operator-(), operator-(), operator/(), and symbol().

◆ ~Expression()

juce::Expression::~Expression ( )

Destructor.

Definition at line 928 of file juce_Expression.cpp.

◆ Expression() [2/5]

juce::Expression::Expression ( const Expression other)

Creates a copy of an expression.

Definition at line 942 of file juce_Expression.cpp.

◆ Expression() [3/5]

juce::Expression::Expression ( Expression &&  other)
noexcept

Move constructor

Definition at line 953 of file juce_Expression.cpp.

◆ Expression() [4/5]

juce::Expression::Expression ( double  constant)
explicit

Creates a simple expression with a specified constant value.

Definition at line 937 of file juce_Expression.cpp.

◆ Expression() [5/5]

juce::Expression::Expression ( const String stringToParse,
String parseError 
)

Attempts to create an expression by parsing a string. Any errors are returned in the parseError argument provided.

Definition at line 964 of file juce_Expression.cpp.

Member Function Documentation

◆ adjustedToGiveNewResult()

Expression juce::Expression::adjustedToGiveNewResult ( double  targetValue,
const Scope scope 
) const

Attempts to return an expression which is a copy of this one, but with a constant adjusted to make the expression resolve to a target value.

E.g. if the expression is "x + 10" and x is 5, then asking for a target value of 8 will return the expression "x + 3". Obviously some expressions can't be reversed in this way, in which case they might just be adjusted by adding a constant to the original expression.

Exceptions
Expression::EvaluationError

Definition at line 1017 of file juce_Expression.cpp.

◆ evaluate() [1/3]

double juce::Expression::evaluate ( ) const

Evaluates this expression, without using a Scope. Without a Scope, no symbols can be used, and only basic functions such as sin, cos, tan, min, max are available. To find out about any errors during evaluation, use the other version of this method which takes a String parameter.

Definition at line 980 of file juce_Expression.cpp.

Referenced by evaluate(), and evaluate().

◆ evaluate() [2/3]

double juce::Expression::evaluate ( const Scope scope) const

Evaluates this expression, providing a scope that should be able to evaluate any symbols or functions that it uses. To find out about any errors during evaluation, use the other version of this method which takes a String parameter.

Definition at line 985 of file juce_Expression.cpp.

◆ evaluate() [3/3]

double juce::Expression::evaluate ( const Scope scope,
String evaluationError 
) const

Evaluates this expression, providing a scope that should be able to evaluate any symbols or functions that it uses.

Definition at line 991 of file juce_Expression.cpp.

◆ findReferencedSymbols()

void juce::Expression::findReferencedSymbols ( Array< Symbol > &  results,
const Scope scope 
) const

Returns a list of all symbols that may be needed to resolve this expression in the given scope.

Definition at line 1075 of file juce_Expression.cpp.

◆ function()

Expression juce::Expression::function ( const String functionName,
const Array< Expression > &  parameters 
)
static

Returns an Expression which is a function call.

Definition at line 1012 of file juce_Expression.cpp.

◆ getInput()

Expression juce::Expression::getInput ( int  index) const

Retrieves one of the inputs to this expression.

See also
getNumInputs

Definition at line 1091 of file juce_Expression.cpp.

◆ getNumInputs()

int juce::Expression::getNumInputs ( ) const

Returns the number of inputs to this expression.

See also
getInput

Definition at line 1090 of file juce_Expression.cpp.

◆ getSymbolOrFunction()

String juce::Expression::getSymbolOrFunction ( ) const

If this expression is a symbol, function or operator, this returns its identifier.

Definition at line 1089 of file juce_Expression.cpp.

◆ getType()

Expression::Type juce::Expression::getType ( ) const
noexcept

Returns the type of this expression.

Definition at line 1088 of file juce_Expression.cpp.

◆ operator*()

Expression juce::Expression::operator* ( const Expression other) const

Returns an expression which is a multiplication operation of two existing expressions.

Definition at line 1007 of file juce_Expression.cpp.

◆ operator+()

Expression juce::Expression::operator+ ( const Expression other) const

Returns an expression which is an addition operation of two existing expressions.

Definition at line 1005 of file juce_Expression.cpp.

◆ operator-() [1/2]

Expression juce::Expression::operator- ( ) const

Returns an expression which performs a negation operation on an existing expression.

Definition at line 1009 of file juce_Expression.cpp.

◆ operator-() [2/2]

Expression juce::Expression::operator- ( const Expression other) const

Returns an expression which is a subtraction operation of two existing expressions.

Definition at line 1006 of file juce_Expression.cpp.

◆ operator/()

Expression juce::Expression::operator/ ( const Expression other) const

Returns an expression which is a division operation of two existing expressions.

Definition at line 1008 of file juce_Expression.cpp.

◆ operator=() [1/2]

Expression & juce::Expression::operator= ( const Expression other)

Copies another expression.

Definition at line 947 of file juce_Expression.cpp.

◆ operator=() [2/2]

Expression & juce::Expression::operator= ( Expression &&  other)
noexcept

Move assignment operator

Definition at line 958 of file juce_Expression.cpp.

◆ parse()

Expression juce::Expression::parse ( String::CharPointerType &  stringToParse,
String parseError 
)
static

Returns an Expression which parses a string from a character pointer, and updates the pointer to indicate where it finished.

The pointer is incremented so that on return, it indicates the character that follows the end of the expression that was parsed.

If there's a syntax error in parsing, the parseError argument will be set to a description of the problem.

Definition at line 972 of file juce_Expression.cpp.

◆ referencesSymbol()

bool juce::Expression::referencesSymbol ( const Symbol symbol,
const Scope scope 
) const

Returns true if this expression makes use of the specified symbol. If a suitable scope is supplied, the search will dereference and recursively check all symbols, so that it can be determined whether this expression relies on the given symbol at any level in its evaluation. If the scope parameter is null, this just checks whether the expression contains any direct references to the symbol.

Exceptions
Expression::EvaluationError

Definition at line 1061 of file juce_Expression.cpp.

◆ symbol()

Expression juce::Expression::symbol ( const String symbol)
static

Returns an Expression which is an identifier reference.

Definition at line 1010 of file juce_Expression.cpp.

Referenced by juce::Expression::Scope::getSymbolValue(), and symbol().

◆ toString()

String juce::Expression::toString ( ) const

Returns a string version of the expression.

Definition at line 1086 of file juce_Expression.cpp.

◆ usesAnySymbols()

bool juce::Expression::usesAnySymbols ( ) const

Returns true if this expression contains any symbols.

Definition at line 1087 of file juce_Expression.cpp.

◆ withRenamedSymbol()

Expression juce::Expression::withRenamedSymbol ( const Symbol oldSymbol,
const String newName,
const Scope scope 
) const

Returns a copy of this expression in which all instances of a given symbol have been renamed.

Definition at line 1049 of file juce_Expression.cpp.


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