Expr does not have object identity have field equality, i.e. julia> Expr(:call, println) == Expr(:call, println) true I was surprised to learn that Expr nevertheless is mutable. I can easily imagine why Expr does not have object identity (“Oh, no, I do not mean to call this println method without …

[image] PatrickHaecker: So why is Expr mutable? One reason might be that Expr existed long before immutable structs were implemented in the language.

Why is `Expr` mutable?

stevengj Split this topic June 14, 2025, 5:42pm 10

9 posts were split to a new topic: How is Symbol special?

Topic		Replies	Views
Assignment and argument passing semantics Offtopic	31	2788	November 4, 2018
A metaprogramming question (sorry, can't find a more informative title) New to Julia	9	888	February 2, 2017
Quoting operator & literals General Usage question	4	872	January 6, 2017
Mutable struct without fields behaving weirdly General Usage	14	3434	February 2, 2018
What's so mutable about `Symbol`s? General Usage	10	1217	January 1, 2018