Mutable Value Semantics Trend vs Immutability

[atravers]

But mutation by itself is troublesome:

By introducing side effects in expressions, the semantics becomes significantly more complex. At the same time, several issues arise, related to the evaluation order, i.e. the order in which the subparts of an expression are evaluated. If the evaluation order is not strictly defined, the presence of side effects in expressions is a source of non-deterministic behaviour.

Denotational Semantics of Evaluation Order in Expressions with Side Effects (1998)

…and mutation is the epitome of side effects! As I mentioned in this post on a related topic:

• arbitrary sequencing but no mutation: confluence.

• arbitrary mutation but no sequencing: nondeterminism!