%false() returns 0 (not false), %true() returns 1 (not true)

Question

Looks the 2 built-in functions %true() and %false() return NOT per http://plantuml.com/ru/preprocessing

is that a bug?

Answer 1

We must state more clearly in the documentation that we follow C/PHP convention here.

So there are no real boolean type.

0 means false and any non-null number (1) means true.

We will update the documentation.