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forth

Why does Forth return -1 as a flag for True?

The Forth code

7 3 > . (7 > 3)

returns -1, but every other language I've ever used uses 1 as a flag for true. Why is this? What accounts for this difference?

Solution

  • -1 is all bits set which then has the benefit that words such as and, or, not, ... serve as both logical and bitwise operators (as opposed to say C with &&, ||, !, ... vs. &, |, ~, ...)