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 …

Why is `Expr` mutable?

GunnarFarneback June 13, 2025, 7:57am 3

One reason might be that Expr existed long before immutable structs were implemented in the language.

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