- TpBool
- TpChar
- TpUChar
- TpShort
- TpUShort
- TpInt
- TpUInt
- TpFloat
- TpDouble
- TpComplex
- TpDComplex
- TpString
- TpTable
- TpArrayBool
- TpArrayChar
- TpArrayUChar
- TpArrayShort
- TpArrayUShort
- TpArrayInt
- TpArrayUInt
- TpArrayFloat
- TpArrayDouble
- TpArrayComplex
- TpArrayDComplex
- TpArrayString
- TpRecord
- TpOther
- TpQuantity
- #// TpLDouble, #// TpArrayLDouble,
- TpArrayQuantity
- TpNumberOfTypes
- Since we start at zero, this is the number of types in the enum.
Also, global functions are written which take a "const pointer to type" and return its DataType (TpOther if unknown). These functions can occasionally allow one to avoid a switch on type, and can be useful in constructing templated classes which are only valid for certain types.
Global functions are also provided which allow one to convert an array type to the equivalent scalar type and vice versa.
New data types should be added just before TpNumberOfTypes, and after all the existing enumerations, to avoid changing the number of an existing type which would cause misinterpretation of data types stored in existing files. Note also that if any new scalar and array types are added that this will break the exising isScalar, isArray, asScalar and asArray functions.
Data types long and unsigned long are not possible. The types Int and uInt are always 4 bytes, so long is not needed and may only cause confusion.
Double d;
DataType type = whatType(&d);
cout << type << endl;
switch(type) {
case TpChar: ...
...
case TpDouble: ...
}
A less obvious use is for "attaching" a templated object or function to a non-templated object in a safe way. For example:
class IntFloatContainer {
public:
Int intval;
Float floatval;
void *ptr(DataType type) {
if (type == whatType(&intval))
return &intval;
else if (type == whatType(&floatval))
return &floatval;
else
return 0; // Illegal type
}
};
template<class T> class ValueAccessor {
public:
ValueAccessor(IntFloatContainer *container) : container_p(container) {
if (container_p->ptr(whatType(static_cast<T *>(0))) == 0)
throw(AipsError("Illegal type..."));
}
T &value() { return *((T*)container_p->ptr(whatType(static_cast<T *>(0)))); }
private:
IntFloatContainer *container_p;
};
So, this example provides a typesafe interface to values of only a small number of types (and it fairly gracefully allows additional types to be added; in particular the accessor class needs no modification). Techniques such as this are appropriate for situations where one needs to deal with many (but finite) numbers of types. For example, with FITS.
Enumeration of the possible data types for keywords and table columns:
enum DataType {TpBool, TpChar, TpUChar,
TpShort, TpUShort, TpInt, TpUInt,
TpFloat, TpDouble,
TpComplex, TpDComplex, TpString,
TpTable,
TpArrayBool, TpArrayChar, TpArrayUChar,
TpArrayShort, TpArrayUShort, TpArrayInt, TpArrayUInt,
TpArrayFloat, TpArrayDouble,
TpArrayComplex, TpArrayDComplex, TpArrayString,
TpRecord, TpOther,
TpNumberOfTypes
};
Write a formated representation (e.g., Type=Bool) of the given data type.
These (overloaded) functions return DataType that corresponds to to the type that is being pointed at. A pointer is used to avoid to avoid having to create the object if it is of Array or Table types. At least for CFront, it also avoids those types from being instantiated (they are forward declared). The void* function matches any type (if none other will), and returns TpOther.
It is sometimes useful to discover what the corresponding scalar (or array) type is for a given array (or scalar) type. Calling these with TpOther, TpTable, and TpRecord results in an exception being thrown.
It is occasionally useful to discover whether or not a DataType represents an array or scalar value. Note that TpTable, TpRecord, and TpOther are neither scalar nor array types.
It is sometimes useful to discover if a DataType represents a real numeric value (i.e., can it be cast to a Double?) This returns True for both real scalar and array type.
Returns True for Complex or DComplex scalar or array types
Returns True if the type is either Real or Complex/DComplex