mixture of rem and mod

mod(x,180) will for any x return the same direction (right sign) but between -90 and +90

For directionalities, somethimes neither rem nor mod is sufficient.
if one direction is -170 degree, this could also be +10, but rem will return -170; mod on the other hand will return 160 for -20; remod will return -20 for -20 and 10 for -170, just as with angles it should.