Function or

or(a: Category, b: Category): Category

Discrete Logical OR:

`a` \ `b`	`undef`	`false`	`never`	`maybe`	`true`
`undef`	`undef`	`undef`	`undef`	`undef`	`undef`
`false`	`undef`	`false`	`never`	`maybe`	`true`
`never`	`undef`	`never`	`never`	`true`	`true`
`maybe`	`undef`	`maybe`	`true`	`maybe`	`true`
`true`	`undef`	`true`	`true`	`true`	`true`

Parameters

a: Category
b: Category

Returns Category