sub - ubtract two numbers or vector
n1 n2 sub -> n3
a1 a2 sub -> a3
5 2 sub -> 3
5.0 2 sub -> 3.0
[5 7] [3 4] sub -> [2 3]
[3 4] 1 sub -> [2 3]
sub can be used to subtract numbers and arrays.
If applied to numbers, sub returns the difference of the numbers. If one
of the arguments is a double, the result is also a double.
Applied to arrays, sub perfoms a per-component subtraction of the two
arrays. The components must be numbers, however, integer and double
values may be mixed.
Note that the two arrays must be of the same size.
docu by Sirko Straube (adopted from add)
/var/www/debian/nest/nest-simulator-2.20.0/lib/sli/mathematica.sli