Where is `===` actually defined?

Internals & Design
1

In operators.jl one sees that ==(x, y) falls back to ===(x, y), but interestingly, ==='s definition in operators.jl is just…

===

I’ve never seen Julia syntax like it! :thinking:

On the repl, one gets:

julia> methods(===)
# built-in function; no methods

So where is === actually defined?
(And what are the cases in which the syntax on operators.jl is valid Julia code?)

2

It’s in Core and isn’t a generic function (you can’t change what it does)

3

The runtime version is called jl_egal, is defined in C and defines the semantics. Obviously there’s lots of optimizations for special cases in different parts of the compiler though.

4

Thank you! In which source file can the code for Core be found?

5

Thank you!

Searching for “jl_egal” in julia’s GitHub repo returns useful stuff, and it’s easy to spot the bit-wise comparison it performs (with memcmp).

How the low-level C function is associated with Julia’s === is the missing piece… perhaps that’s what’s in Core, whose source code I’m still to find.

6

All builtins are defined as c functions and most if not all are in builtins.c. You can find all the relevant code by searching for === in src/ and ignoreing all the ones in comments…