Unigine::Expression Class

This class allows you to execute a given code fragment at run-time. There can be up to 4 arguments of any type passed to the Expression. The setVariable() function sets values of such arguments. For example:

Source code (C++)

Expression e0 = Expression(Engine::get()->getWorldInterpreter(), "133.0 * 133.0");
if (e0.isCompiled()) {
	Log::message("%f\n", e0.run().getFloat());
}

Expression e1 = Expression(Engine::get()->getWorldInterpreter(), " \
	{\
		int a, b, c, d; \
		return a + b + c + d; \
	}\
");

e1.setVariable("a", Variable(1));
e1.setVariable("b", Variable(2));
e1.setVariable("c", Variable(3));
e1.setVariable("d", Variable(4));

if (e1.isCompiled()) {
	Log::message("%d\n", e1.run().getInt());
}

Expression e2 = Expression(Engine::get()->getWorldInterpreter(), "\
	{\
		string name;\
		File file = new File(name, \"rb\");\
			int size = file.getSize();\
		file.close();\
		delete file;\
		return size;\
	}\
");
e2.setVariable("name", Variable("test.cpp"));
if (e2.isCompiled()) {
	Log::message("%d\n", e2.run().getInt());
}

Output

double: 17689
int: 10
int: 1302

Methods:

Name	Description View: Sort by:
Expression	Constructor.
isCompiled	Returns a value indicating if the given expression has been compiled.
getFunction	Returns the ID of the function from the expression namespace.
isFunction	Checks if a given user-defined function exists in the expression namespace.
setName	Sets a namespace name for the expression that can be used when calling expression methods.
getName	Get a name used as a namespace name when calling expression methods.
setVariable	Set the value of the variable from the expression namespace by its name.
getVariable	Returns ID of the variable from the expression namespace.
isVariable	Checks if a given user-defined variable exists in the expression namespace.
run	Runs the given expression.
saveState	Saves the expression data (all its parameters) to the specified binary stream.
restoreState	Restores the data of the expression (all its parameters) from the specified binary stream.

Expression Class

Members

Expression ( void * interpreter, const char * src, int scope = 0 ) #

Constructor. Creates the expression from the specified source buffer.

Arguments

void * interpreter - Interpreter pointer.
const char * src - Source buffer pointer. Source buffer is a string containing expression's source code.
int scope - 1 to treat the expression namespace as the global; otherwise, 0 (by default).

int isCompiled ( ) #

Returns a value indicating if the given expression has been compiled.

Return value

1 if the expression has been compiled; otherwise, 0.

int getFunction ( const char* name, int num_args ) #

Returns the ID of the function from the expression namespace. It can be used to call a function by its ID instead of the name (speeds up the function call; it is almost as fast the direct call).

Arguments

const char* name - Name of the function.
int num_args - Number of function arguments.

Return value

Function ID.

int isFunction ( const char* name, int num_args ) #

Checks if a given user-defined function exists in the expression namespace.

Arguments

const char* name - Full name of the target function.
int num_args - Number of arguments of the target function.

Return value

1 if the function exists; otherwise, 0.

void setName ( const char* name ) #

Sets a namespace name for the expression that can be used when calling expression methods.

Arguments

const char* name - Namespace name.

const char* getName ( ) #

Get a name used as a namespace name when calling expression methods.

Return value

Namespace name.

void setVariable ( const char* name, variable value ) #

Set the value of the variable from the expression namespace by its name.

Arguments

const char* name - Variable name.
variable value - Variable value to set.

variable getVariable ( const char* name ) #

Returns ID of the variable from the expression namespace. It can be used to pass a variable by its ID instead of the name. It speeds up passing of the variable and can be used when performance is crucial.

Arguments

const char* name - Variable name.

Return value

Variable, if it exists; otherwise, 0.

int isVariable ( const char* name ) #

Checks if a given user-defined variable exists in the expression namespace.

Arguments

const char* name - Name of the target variable.

Return value

1 if the variable exists; otherwise, 0.

variable run ( ) #

Runs the given expression.

Return value

Argument value.

bool saveState ( const Ptr<Stream> & stream ) #

Saves the expression data (all its parameters) to the specified binary stream.

Example using saveState() and restoreState() methods:

Source code (C++)

// initialize an expression and set its state
//...//

// save state
BlobPtr blob_state = Blob::create();
e1->saveState(blob_state);

// change state
//...//

// restore state
blob_state->seekSet(0);				// returning the carriage to the start of the blob
e1->restoreState(blob_state);

Arguments

const Ptr<Stream> & stream - Stream to which the expression data will be saved.

Return value

true if the expression data is saved successfully; otherwise, false.

bool restoreState ( const Ptr<Stream> & stream ) #

Restores the data of the expression (all its parameters) from the specified binary stream.

Example using saveState() and restoreState() methods:

Source code (C++)

// initialize an expression and set its state
//...//

// save state
BlobPtr blob_state = Blob::create();
e1->saveState(blob_state);

// change state
//...//

// restore state
blob_state->seekSet(0);				// returning the carriage to the start of the blob
e1->restoreState(blob_state);

Arguments

const Ptr<Stream> & stream - Stream in which the saved expression data is stored.

Return value

true if the expression data is restored successfully; otherwise, false.

Last update: 2022-03-10

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