18.7 Mapping for Built-In Types

The Slice built-in types are mapped to Objective‑C types as shown in Table 18.1.

Table 18.1. Mapping of Slice built-in types to Objective‑C.

Slice	Objective‑C
bool	BOOL
byte	ICEByte
short	ICEShort
int	ICEInt
long	ICELong
float	ICEFloat
double	ICEDouble
string	NSString or NSMutableString

Slice bool maps to Objective‑C BOOL. The remaining integral and floating-point types map to Objective‑C type definitions instead of native types. This allows the Ice run time to provide a definition as appropriate for each target architecture. (For example, ICELong might be defined as long on one architecture and as long long on another.)

Note that ICEByte is a typedef for unsigned char. This guarantees that byte values are always in the range 0..255, and it ensures that right-shifting an ICEByte does not cause sign-extension.

Whether a Slice string maps to NSString or NSMutableString depends on the context. NSMutableString is used in some cases for operation parame­ters; otherwise, if a string is a data member of a Slice structure, class, or excep­tion, it maps to NSString. (We will discuss these differences in more detail as we cover the mapping of the relevant Slice language features.)