Why is the ternary operator used to define 1 and 0 in a macro?

Why is the ternary operator used to define 1 and 0 in a macro?

c++ c boolean ternary-operator

c

The ternary (conditional) operator in C

c operators ternary-operator conditional-operator

c

?: ternary conditional operator behaviour when leaving one expression empty

c ternary-operator conditional-operator ternary

c

Is this ternary conditional ?: correct (Objective) C syntax?

objective-c c ternary-operator conditional-operator

c

C conditional operator ('?') with empty second parameter [duplicate]

c operators conditional ternary-operator

c

Ternary expression which "does nothing" (noop) if the condition is false?

c++ objective-c c ternary-operator

c