Basic types
Primitive types
The primitive types are:
bool |
Boolean type; false or true.
|
char8 |
Single byte in a UTF-8 string. This is not a numeric type. |
nat8,
nat16,
nat32,
nat64
|
Natural numbers, in the range 0 to 2n - 1.
nat is short for nat64.
|
int8,
int16,
int32,
int64
|
Integers, in the range -2n - 1 to 2n - 1 - 1.
int is short for int64.
|
float32, float64 |
Floating-point values.
float is short for float64.
|
Arithmetic
nat and int arithmetic
always returns an exactly correct result or throws an exception.
float arithmetic doesn't have such checks,
since floats are usually expected to be inexact.
Conversion
There is no dedicated syntax for conversion,
but a function should be named to if it does an obvious conversion.
This relies on type inference which will be explained more in Type inference.
As with arithmetic, conversions between nat/int types will throw if they can't return an exact result.
Strings
These are similar to other programming languages.
Strings are represented as a char8[],
but when iterated they decode to char32s.
(In a JavaScript build, strings represented as are JS strings.)
String syntax
Basic string syntax is similar to C: "hello".
They support the same escape sequences, like "hello\nworld".
There are also triple-quoted strings that allow newlines in the string.
String interpolation
You've seen this a lot already.
"1 + 1 is {1 + 1}!" is shorthand for
("1 + 1 is ", (1 + 1).show, "!") interpolate.
(interpolate just concatenates its inputs.)
show is a conventional name for a function that renders its argument to a string.
String functions
String functions are in string.
A string is also a collection of char32,
so many functions in col/collection will work on strings.
Symbols
Strings are often used simply as identifiers or like ad-hoc enums.
In crow, you should instead use symbols for those use cases.
A symbol is a unique identifier that comes from a string.
The string is interned,
meaning that two separately-allocated strings that are equal will only result in a single allocated symbol.
So, two symbols are equal if their pointers are equal.
That means == on symbols is fast, making them good as a key in a map.
The literal syntax for a symbol is the same as for a string.
As usual, to convert between strings and symbols, call the to function.
Tuples
You've already seen tuples in the section on destructuring in Local variables.
The syntax for a tuple type is like (nat, string) or (nat, string, float).
It can have up to 9 members. It can't have less than 2.
A tuple type is often created implicitly by a destructuring,
as in n nat, s string declaring a (nat, string) tuple.