The engine's synchronous resolver of host functions, one for every
view and every surface's declarations. Invoked on the thread evaluating
the expression, during resolution and action evaluation: it must be
fast, must not block, must not touch the view, and must be pure over
its arguments (vocabulary schema spec, Function declarations). The value
is validated against the declared returns; a mismatch or a throw is
an invalid function result, reported and replaced by the zero value of
the return type. Returning null is the null value.
The engine's synchronous resolver of host functions, one for every view and every surface's declarations. Invoked on the thread evaluating the expression, during resolution and action evaluation: it must be fast, must not block, must not touch the view, and must be pure over its arguments (vocabulary schema spec, Function declarations). The value is validated against the declared
returns; a mismatch or a throw is an invalid function result, reported and replaced by the zero value of the return type. Returningnullis the null value.