Bit masking tricks (though Leo Brodie objected to calling that kind of code a 'trick'). Kind of amusing history: in FORTH-79 tests returned 1 for true, then FOR

Bit masking tricks (though Leo Brodie objected to calling that kind of code a 'trick'). Kind of amusing history: in FORTH-79 tests returned 1 for true, then FORTH-83 changed it, and also changed NOT to mean bitwise complement because you could use 0= for logical complement. Confusion! In the next standard NOT was left undefined, or rather they changed the name to INVERT.