Unpacking vector / swizzle notation

[bvssvni]

Example:

(
    f(1, 0, 0),
    f(0, 1, 0),
    f(0, 0, 1),
    0,
)

Can be written as:

vec4 j {
    v := vec4 i (if i == j { 1 } else { 0 })
    if j == 3 { 0 } else { f(x(v), y(v), z(v)) }
}

Could add a notation for unpacking a vector:

vec4 j (if j == 3 { 0 } else { f(xyz vec4 i (if i == j { 1 } else { 0 }) })

Swizzling

Could use a similar notation for swizzling:

u := (zxy v, 0)

vec2/vec3

Could add vec2 and vec3 for setting last components to 0:

vec3 j f(xyz vec3 i (if i == j { 1 } else { 0 })