Scalar

Creating Scalars

Scalars created in the following examples are stored in ConstantSP. The basic data type definitions are declared in the header files <ScalarImp.h> and <ConstantImp.h>.

The DolphinDB C++ API provides two methods for creating scalars:

(1) Use new expression.

ConstantSP i = new Int(1);                          //create a scalar of type Int with value 1
ConstantSP s = new String("DolphinDB");             //create a scalar of type String with value "DolphinDB"
ConstantSP t = new Date(2022, 11, 1);               //create a scalar of type Date with value 2022.11.1
ConstantSP d = new Double(1.2);                     //create a scalar of type Double with value 1.2

(2) Use functions provided in the header <Util.h>.

ConstantSP i = Util::createInt(1);
ConstantSP s = Util::createString("DolphinDB");
ConstantSP t = Util::createDate(2022, 11, 1);
ConstantSP d = Util::createDouble(1.2);

Accessing Scalars

To access a scalar, use the corresponding get function. For detailed data type mappings, see Data Types and Forms.

Note: The getString() function can be applied to data objects of any data type to convert their values to strings.

int ci          = i->getInt();
std::string cs  = s->getString();
int cd          = t->getInt();         //The Date values in C++ are stored as int. 
double cv       = d->getDouble();

Updating Scalars

To update a scalar, use the corresponding set function. For detailed data type mappings, see Data Types and Forms.

i->setInt(2);
s->setString("C++ API");
t->setInt(5000);              //Number of days to January 1, 1970
d->setDouble(2.3);