► |  | FFI: PLT Scheme Foreign Interface

1 | Overview
2 | Loading Foreign Libraries
3 | C Types
4 | Pointer Functions
5 | Miscellaneous Support
6 | Derived Utilities
7 | Unexported Primitive Functions
8 | Macros for Unsafety
| Index

▼ | 3 | C Types

3.1 | Type Constructors
3.2 | Numeric Types
3.3 | Other Atomic Types
3.4 | String Types
3.5 | Pointer Types
3.6 | Function Types
3.7 | C Struct Types
3.8 | Enumerations and Masks

On this page:

_ enum
_ bitmask

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#### 3.8`` Enumerations and Masks

Although the constructors below are describes as procedures, they are implemented as syntax, so that error messages can report a type name where the syntactic context implies one.

(_enum symbols [basetype]) → ctype?
symbols : list?
basetype : ctype? = _ufixint

Takes a list of symbols and generates an enumeration type. The enumeration maps between a symbol in the given symbols list and corresponding integers, counting from 0.

The list symbols can also set the values of symbols by putting '= and an exact integer after the symbol. For example, the list '(x y = 10 z) maps 'x to 0, 'y to 10, and 'z to 11.

The basetype argument specifies the base type to use.

(_bitmask symbols [basetype]) → ctype?
symbols : (or symbol? list?)
basetype : ctype? = _uint

Similar to _enum, but the resulting mapping translates a list of symbols to a number and back, using bitwise-ior. A single symbol is equivalent to a list containing just the symbol. The default basetype is _uint, since high bits are often used for flags.
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