I have been porting old APL*PLUS PC functions that run on DOS to Dyalog and have had great success. But one function runs fine on APL*PLUS PC but gave me a DOMAIN ERROR on Dyalog. I traced the problem to a matrix invertion using ⌹.
Here is an example of what I am seeing:
F←6.91E9 5.655E9
I←¯0.0144722 ¯0.01897385
Z←I⌹2 2⍴F[1],(÷-F[1]),F[2],÷-F[2]
DOMAIN ERROR
Z←I⌹2 2⍴F[1],(÷-F[1]),F[2],÷-F[2]
∧
This error was also observed on GNU_64 APL.
I created my own DIVIDE function to work with 2x2 arrays:
Z←I2 DIVIDE M22;A;B;C;D
A←M22[1;1] ⋄ B←M22[1;2] ⋄ C←M22[2;1] ⋄ D←M22[2;2]
Z←÷(A×D)-B×C
Z←Z×(2 2)⍴D,(-B),(-C),A
Z←Z+.×I2
Z←I DIVIDE 2 2⍴F[1],(÷-F[1]),F[2],÷-F[2]
Z
4.625648461E¯13 122089494.5
Check answer:
(2 2⍴F[1],(÷-F[1]),F[2],÷-F[2])+.×Z
¯0.0144722 ¯0.01897385
DIVIDE gives the correct answer
