(
d1 | ud1 n --
d2 | ud2 )
Add
n to
d1 | ud1, giving the sum
d2 | ud2.
Rationale:
M+ is the classical method for integrating.
Testing:
T{ HI-2INT 1 M+ -> HI-2INT 1. D+ }T
T{ MAX-2INT -1 M+ -> MAX-2INT -1. D+ }T
T{ MIN-2INT 1 M+ -> MIN-2INT 1. D+ }T
T{ LO-2INT -1 M+ -> LO-2INT -1. D+ }T