require "math"

function table.shallow_copy(t)
    local t2 = {}
    for k,v in pairs(t) do
        t2[k] = v
    end
    return t2
end

function thisorthat(c, a, b)
    if c then return a else return b end
end

function pingpong(at, over)
    local c = (over - 1) * 2
    if math.fmod(at, c) >= over then
        return c - math.fmod(at, c)
    else
        return math.fmod(at, c)
    end
end

function linease(c, t, d, b)
    return c * t / d + b
end

function sinease(c, t, d, b)
    return -c*math.cos(t/d*(math.pi/2)) + c + b
end

function vec3_cross(a, b)
    return {
        x = a.y * b.z - a.z * b.y,
        y = a.z * b.x - a.x * b.z,
        z = a.x * b.y - a.y * b.x,
    }
end

function vec3_dot(a, b)
    return a.x * b.x + a.y * b.y + a.z * b.z
end

function vec3_scale(a, s)
    return {
        x = a.x * s,
        y = a.y * s,
        z = a.z * s,
    }
end

function vec3_norm(a)
    return vec3_scale(a, 1.0 / math.sqrt(vec3_dot(a, a)))
end

function vec3_add(a, b)
    return { x = a.x + b.x, y = a.y + b.y, z = a.z + b.z }
end

function vec3_sub(a, b)
    return { x = a.x - b.x, y = a.y - b.y, z = a.z - b.z }
end

function vec3_length(a)
    return math.sqrt(a.x * a.x + a.y * a.y + a.z * a.z)
end