— Escape: \ni
— Escape: \n(id
— Escape: \n[ident]

Interpolate number register with name ident (one-character name i, two-character name id). This means that the value of the register is expanded in-place while gtroff is parsing the input line. Nested assignments (also called indirect assignments) are possible.

          
          .nr a 5
          .nr as \na+\na
          \n(as
              ⇒ 10

          
          .nr a1 5
          .nr ab 6
          .ds str b
          .ds num 1
          \n[a\n[num]]
              ⇒ 5
          \n[a\*[str]]
              ⇒ 6