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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

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: 03.02.2021
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