[spec] Specify Logic Resource. (#266)

specification/hugr.md

@@ -1675,6 +1675,24 @@ implementation of this design document is available on GitHub.
 `panic`: panics unconditionally; no inputs, any type of outputs (these
 are never produced)
 
+### Logic Resource
+
+The Logic Resource provides a boolean type and basic logical operations.
+
+The boolean type `bool` is defined to be `Sum((),())`, with the convention that the
+first option in the sum represents "false" and the second represents "true".
+
+The following operations are defined:
+
+| Name | Inputs | Outputs | Meaning |
+| -------- | ---------- | ------- | ----------------------------- |
+| `not` | `bool` | `bool` | logical "not" |
+| `and<N>` | `bool` x N | `bool` | N-ary logical "and" (N \>= 0) |
+| `or<N>` | `bool` x N | `bool` | N-ary logical "or" (N \>= 0) |
+
+Note that an `and<0>` operation produces the constant value "true" and an
+`or<0>` operation produces the constant value "false".
+
 ### Arithmetic Resource
 
 The Arithmetic Resource provides types and operations for integer and