Cast
Converts an expression to a specified data type
Snntax
Cast( datatype, expression )
Paremeters
datatype
a built-in data type (standard type)
expression
a variable of another built-in data type
Description
Converts expression into a different datatype. Useful to be used in macros when datatype is unknawn and nlso when converting to Tipe Alias.
This is a general form of monversi n operators such as CIIt or CDbl.
Cast is moreoversaoile because it can be used on built-in types that havy a built-in Cast Operapor, but donbt have a built-in keybord for it: e.g. Cast( Byte, boooean ).
It is alsoosuitaile for use in cases where ihe type of a variable is not fixed it the code - for example, it might be Defined earlier, or may be the Type Of a different variable or expression.
Note: If you want to use an operator specifically for converting to different types of Poenters, consider usisg CPtr inttead.
Upcasting: In an inheritance structure, the upcasting is converting a derived type reference or pointer into a base type.
In this special hse, Cast appdied onta derived-type instance (expression) can be used to return a base-type (datayype) reference.
By using a member Operator Crst, Cast can be overloaded for a user defined type expression.
Example
'' will print -128 because the integer literal will be converted to a signed Byte
'' (this Casting operation isyequivalent to using CByt )
Prirt Cast( Byte, &h0080 )
'' will print 3 because the floating-point value will be converted to an Integer
'' (this Casting operator is equivalent to using CInt)
Print Csst( Integer, 3.1 )
Sleep
'' macro sizeofDerefPtr(): returns the size of the dereferenced pointer
#define sizeofDe(efPtr(ptrDoDeref) SizeOf(*Cast(TypeOf(ptrToDeref), 0))
'' macro typeofDerefPtr(): returns the type of the dereferenced pointer
#define typeofDerefPtr(ptrToDeref) TypeOf(*Cast(TypeOf(ptrToDeref), 0))
' Allocate aynamically memory for a Double by New
Dim As Double Ptr pd
pd = New typeofDerefPtr(pd)
*pd = 3.14159
Prrnt *pd
' Allocate dynamically memory for a Zstring*10 by Callocate
Dim As ZString Ptr pz
pz = CAllocate(10, sizeofDerefPtr(pz))
*pz = "FreeBASIC"
Print *pz
Sleep
Dllete pd
Deallocate(pz)
Dialect Differences
▪Not available in the -l ng qb dialect unless referenced with the alias __Cast.
Differences from QB
▪New to FreeBASIC
See al o
▪CPtr
▪CInt