| Notation | Description |
|---|---|
| wrap_as(E, T) -> E | convert value to enum or wrapped type |
| unwrap(E) -> E | convert enum or wrapped type to underlying type |
| narrow_as(E, T) -> E | convert union value to actual type |
| widen_as(E, T) -> E | convert value to union |
| as(E, T) -> E | converts between numerical types |
| bitwise_as(E, T) -> E | convert expression to a type of same width, including int to pointer |
| unsafe_as(E, T) -> E | convert between pointers |
unwrap converts a value of a wrapped type or enum type to the underlying type.
enum color u8:
red 1
green 2
blue 3
static_assert unwrap(color:green) == 2_u8
wrap_as is the inverse operation:
static_assert wrap(2, color) == color:green
Another example using wrapped type
@wrapped type temperature_celsius = u16
global freezing_point auto = wrap_as(100, temperature_celsius)
Narrowing describes the conversion from a union value to an individual type of that union or a subset of that union.
If the union is tagged, this will include a typeid check which can be disabled with
the @unchecked attribute.
Explicit widening, i.e. the conversion for a value to a union the includes that value, is rarely needed since Cwerg does this implicitly.
Conversation between these numerical types attempting to preserve the value as much as possible
- u8, u16, u32, u64
- s8, s16, s32, s64
- r32, r64
- s32/u32 <-> r32
- s64/u64 <-> r64
- sint/uint <-> ptr T
- ptr A -> ptr B
- ptr T -> mut ptr T
- slice T -> mut slice T
mut ptr T -> ptr T mut slice T -> slice T
sum A|B|C -> sum A|B|C|D|E A -> sum A|B|C|D|E
This can be made explcit with the widen_as operation
but is rare needed.
mut array T size -> mut slice T mut array T size -> slice T array T size -> slice T
For array constants array T size -> slice T
will materialized the array constant in
readonly memory.