Docs say that type annotations on variables and return types of functions facilitate type inference and performance. But does the opposite hold? If I have a function: function foo(x)::Number if isa(x, Number) return x else return 0 end end Will the convert(Number, ...) …

Julia has excellent tools to answer those questions :slight_smile: E.g. use @code_warntype and @code_lowered to figure out what happens (you can use ?@code_lowered in the REPL to get the doc string for those macros): julia> function foo(x)::Number if isa(x, Number) retur…

Performance of type annotations

Internals & Design

julbinb January 4, 2018, 11:35am 3

@sdanisch Indeed, thanks a lot!

Topic		Replies	Views
Type-annotate vs convert General Usage	6	1286	June 23, 2017
Type inference for return types? New to Julia	5	585	February 18, 2022
Should Julia raise errors for illegal return type annotation? Internals & Design	6	2662	September 4, 2021
Semantics of :: in return type vs. argument type annotations General Usage	77	2383	March 1, 2024
On type annotations New to Julia	88	3140	March 8, 2025

Performance of type annotations

Related topics