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: 1302Expression 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
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
Return value
true if the expression data is restored successfully; otherwise, false.Last update:
2021-02-03
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