8.6.1.1040 D+ d-plus DOUBLE
Add d2 | ud2 to d1 | ud1, giving the sum d3 | ud3.
Testing:
T{ -5. 0. D+ -> -5. }T
T{ 1. 2. D+ -> 3. }T
T{ 1. -2. D+ -> -1. }T
T{ -1. 2. D+ -> 1. }T
T{ -1. -2. D+ -> -3. }T
T{ -1. 1. D+ -> 0. }T
T{ 0 0 0 5 D+ -> 0 5 }T \ mid range integers
T{ -1 5 0 0 D+ -> -1 5 }T
T{ 0 0 0 -5 D+ -> 0 -5 }T
T{ 0 -5 -1 0 D+ -> -1 -5 }T
T{ 0 1 0 2 D+ -> 0 3 }T
T{ -1 1 0 -2 D+ -> -1 -1 }T
T{ 0 -1 0 2 D+ -> 0 1 }T
T{ 0 -1 -1 -2 D+ -> -1 -3 }T
T{ -1 -1 0 1 D+ -> -1 0 }T
T{ MIN-INT 0 2DUP D+ -> 0 1 }T
T{ MIN-INT S>D MIN-INT 0 D+ -> 0 0 }T
T{ HI-2INT 1. D+ -> 0 HI-INT 1+ }T \ large double integers
T{ HI-2INT 2DUP D+ -> 1S 1- MAX-INT }T
T{ MAX-2INT MIN-2INT D+ -> -1. }T
T{ MAX-2INT LO-2INT D+ -> HI-2INT }T
T{ LO-2INT 2DUP D+ -> MIN-2INT }T
T{ HI-2INT MIN-2INT D+ 1. D+ -> LO-2INT }T