# Takes 16 bits of space, but only uses the last 4 bits
flags FontStyle(16, 4): Show {
    # Nothing will be generated even if it is not written, you can rename `0` to any other name
    Nothing    = 0,
    Bold       = 2 ^ 0,
    Italic     = 2 ^ 1,
    Underline  = 2 ^ 2,
    Red        = 2 ^ 3,
    RedBold    = 2 ^ 3 + 2 ^ 0,
    RedItalic  = Red | Italic,
    # Everything will be generated according to the upper limit even if it is not written
    Everything = 2 ^ 4 - 1,
}

Valkyrie has no bit level operator, so you can only use 2 ^ 0 instead of 1 << 0, use 2 ^ 3 + 2 ^ 0 instead of 1 << 3 | 1 << 0.

The numbers or operations on the right are compile time big integers, instead of dynamic values.

Flags cannot extend a value or function that takes no arguments and returns its own type, as this would lead to confusion

All associated constant values must be written in the flags declaration, and does not support duplicate values.

Global variables are not subject to this.

Operators

• a | b: bit set or, returns a new Flags with the bits of both Flags set to 1.
• a & b: bit set and, returns a new Flags with the bits of both Flags set to 1.
• a + b: same as a | b
• a - b: bit set difference, returns a new Flags with the bits of the left Flags set to 1 and the bits of the right Flags set to 0.
• -a: bit set negation, invert 0 and 1 bits according to Flags::Everything
• !a: same as -a
• Flags::Name: create a new Flags with bits according to the definition.

Type Conversion

As Integer

Flags and Integer cannot be replaced arbitrarily, you need to use as? to convert. In Valkyrie, as? returns Result<T, ConvertError>.

Converting between Integer and Flags is not free, the layout of Integer is [u32], and cannot be directly truncated to [u8].

Also, you can pass Integer to any function parameter that accepts Flags.

micro render(text: String, style: FontStyle): String {
    if style == FontStyle::RedBold {
        return '<b style="color: red">{text}</b>'
    }
    if style.has(FontStyle::Red) {
        return '<span style="color: red">{text}</span>'
    }
    if style.has(FontStyle::Bold) {
        return '<b>{text}</b>'
    }
}
render('Hello, World!', 9)  #ok

But if the Integer is greater than the maximum value of Flags, the large integer will be truncated according to the Layout of Flags, and no error will be raised.

As String

imply FontStyle: Show {
    show(self)
}