Perl 6 native types
Using the types the compiler and hardware make available to you
Perl 6 offers a set of native types with a fixed, and known, representation in memory. This page shows which ones exist and how they can be used. Please check also the page on native numerics for more information on them.
Some simple types in Perl 6 have a native representation, indicating that they will use the C language representation provided by the compiler, operating system and machine. These are the four native types available:
|int||Equivalent to Int (with limited range)|
|uint||Equivalent to Int (with limited range) with the unsigned trait|
|num||Equivalent to Num|
|str||Equivalent to Str|
However, these types do not necessarily have the size that is required by the NativeCall interface (e.g., Perl 6's
int can be 8 bytes but C's
int is only 4 bytes); the types below will have to be used instead of the types
num listed above.
In general, these variables will behave in the same way as regular scalar variables, in a behavior that is called auto-boxing; however, there are some differences, since what you are actually declaring is how they will be represented, not their actual type. The first one is that their type will be actually their equivalent type, not their native type.
my int = 3;say .^name; # OUTPUT: «Int␤»
This obviously means that they will smartmatch their equivalent (auto-boxed) type, not their native type:
my str = "tres";say ~~ str; # OUTPUT: «False␤»say ~~ Str; # OUTPUT: «True␤»
And also that they will always have a default value, unlike their non-native counterparts:
say (my Str $); # OUTPUT: «(Str)␤»say (my str $); # OUTPUT: «␤»say (my num $); # OUTPUT: «0␤»
Note: In v6.c, the default value for
num would have been a NaN.
This is due to the fact that Natives don't know their types because they're just values, without any meta-data. In multi-dispatch, you can have a native candidate, but you cannot differentiate different sizes of the same native type. That is, you can have an Int and int candidates, but there would be an ambiguity between int, atomicint, int64, etc. candidates.
They cannot be bound either. Trying to do
my num $numillo := 3.5 will raise the exception
Cannot bind to natively typed variable '$variable-name'; use assignment instead.
my int = ^10_000_000;say [+] ; # OUTPUT: «49999995000000␤»
my num = ^8 »*» π ; say .^name; # OUTPUT: «array[num]␤»
my str  = 'a'..'j' Z~ 'A'..'J';say .perl;# OUTPUT: «array[str].new(:shape(10,), ["aA", "bB", "cC", "dD", "eE", "fF", "gG", "hH", "iI", "jJ"])␤»
What has been mentioned about types with native representation also applies here; they will be auto-boxed to Perl 6 types and will not be boundable. However, these types, which are listed in the table below, have the characteristic of being usable in NativeCall functions.
|int8||(int8_t in C, also used for char)|
|int16||(int16_t in C, also used for short)|
|int32||(int32_t in C, also used for int)|
|int64||(int64_t in C)|
|byte, uint8||(uint8_t in C, also used for unsigned char)|
|uint16||(uint16_t in C, also used for unsigned short)|
|uint32||(uint32_t in C, also used for unsigned int)|
|uint64||(uint64_t in C)|
|num32||(float in C)|
|num64||(double in C)|
These types have a fixed size representation which is independent of the platform, and thus can be used safely for those native calls. Nothing prevents us from using them in any other environment, if we so wish. In the same way as the types above, this size will have to be taken into account when assigning values to variables of this type:
my byte = 257;say ; # OUTPUT: «1␤»
byte is able to hold only 8 bits, it will wrap over and assign the result of the original value modulo 256, which is what is shown.
The main difference between types with declared native size and those without is the use of is nativesize in their declaration. For instance,
int8 is declared in this way:
my native int8 is repr('P6int') is Int is nativesize( 8)
Indicating that it will use, besides an integer representation (
P6int), a native size of only 8 bits. This trait, however, is not intended to be used in your programs since it is not part of the Perl 6 specification.
void type corresponds to the C
void type. Although, being a valid type, you can use it in expressions:
use NativeCall;my void ;say .perl; # OUTPUT: «NativeCall::Types::void␤»
In practice, it is an
Uninstantiable type that can rarely be used by itself, and in fact it is explicitly forbidden in
return types. However, it is generally found in typed pointers representing the equivalent to the
void * pointer in C.
sub malloc( int32 --> Pointer[void] ) is native ;my Pointer[void] = malloc( 32 );say .perl;
use NativeCall;my Pointer[void] = nativecast(Pointer[void], Blob.new(0x22, 0x33));
However, outside that, the functionality it offers is quite limited, since pointers to void cannot be dereferenced:
use NativeCall;my Pointer[void] = nativecast(Pointer[void], Buf.new(0x22, 0x33));say .deref; # ERROR OUTPUT: «Internal error: unhandled target type␤»
In this context, atomic refers to safe operation under threading. Perl 6 provides a type,
atomicint, and some operations which, together, guarantee this. Please check the atomic operations section on the Numerics page for more information on this.
The types described in this section are Rakudo specific, so they are not guaranteed to be in other implementations or remain the same in future versions.
|long||(long in C)|
|longlong||(longlong in C)|
|ulong||(long and unsigned in C)|
|ulonglong||(longlong and unsigned in C)|
|size_t||(size_t and unsigned in C)|
|ssize_t||(size_t in C)|
|bool||(bool in C)|
You can use them in the same way they would be used in native C:
use NativeCall;my = CArray[int32].new( 1, 2, 3, 4, 5 );loop ( my size_t = 0; < .elems; ++ )
Which would print the five elements of the array, as it should be expected.