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juce::Expression Class Reference

#include <juce_core.h>

Classes

struct  Helpers
 
class  ParseError
 
class  Scope
 
struct  Symbol
 
class  Term
 

Public Types

enum  Type { constantType, functionType, operatorType, symbolType }
 

Public Member Functions

 Expression ()
 
 ~Expression ()
 
 Expression (double constant)
 
 Expression (const Expression &)
 
Expressionoperator= (const Expression &)
 
 Expression (const String &stringToParse)
 
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)
 

Friends

class Term
 
struct Helpers
 
struct ContainerDeletePolicy< Term >
 
class ReferenceCountedObjectPtr< Term >
 

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.

Member Enumeration Documentation

◆ Type

Expression type.

See also
Expression::getType()
Enumerator
constantType 
functionType 
operatorType 
symbolType 

Constructor & Destructor Documentation

◆ Expression() [1/4]

Expression::Expression ( )

Creates a simple expression with a value of 0.

◆ ~Expression()

Expression::~Expression ( )

Destructor.

◆ Expression() [2/4]

Expression::Expression ( double  constant)
explicit

Creates a simple expression with a specified constant value.

◆ Expression() [3/4]

Expression::Expression ( const Expression other)

Creates a copy of an expression.

◆ Expression() [4/4]

Expression::Expression ( const String stringToParse)
explicit

Creates an expression by parsing a string. If there's a syntax error in the string, this will throw a ParseError exception.

Exceptions
ParseError

Member Function Documentation

◆ adjustedToGiveNewResult()

Expression 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

◆ evaluate() [1/3]

double 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.

◆ evaluate() [2/3]

double 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.

◆ evaluate() [3/3]

double 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.

◆ findReferencedSymbols()

void 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.

◆ function()

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

Returns an Expression which is a function call.

◆ getInput()

Expression Expression::getInput ( int  index) const

Retrieves one of the inputs to this expression.

See also
getNumInputs

◆ getNumInputs()

int Expression::getNumInputs ( ) const

Returns the number of inputs to this expression.

See also
getInput

◆ getSymbolOrFunction()

String Expression::getSymbolOrFunction ( ) const

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

◆ getType()

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

Returns the type of this expression.

◆ operator*()

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

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

◆ operator+()

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

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

◆ operator-() [1/2]

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

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

◆ operator-() [2/2]

Expression Expression::operator- ( ) const

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

◆ operator/()

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

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

◆ operator=()

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

Copies another expression.

◆ parse()

Expression Expression::parse ( String::CharPointerType stringToParse)
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 the string, this will throw a ParseError exception.

Exceptions
ParseError

◆ referencesSymbol()

bool 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

◆ symbol()

Expression Expression::symbol ( const String symbol)
static

Returns an Expression which is an identifier reference.

◆ toString()

String Expression::toString ( ) const

Returns a string version of the expression.

◆ usesAnySymbols()

bool Expression::usesAnySymbols ( ) const

Returns true if this expression contains any symbols.

◆ withRenamedSymbol()

Expression 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.

Friends And Related Function Documentation

◆ ContainerDeletePolicy< Term >

friend struct ContainerDeletePolicy< Term >
friend

◆ Helpers

friend struct Helpers
friend

◆ ReferenceCountedObjectPtr< Term >

friend class ReferenceCountedObjectPtr< Term >
friend

◆ Term

friend class Term
friend

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