Assignment for mutable records

First, we understand that records are partial functions: properties -> location

Semantic domain extension

Include bottom in the event we access an undefined record attribute.

As arguments to functions

  1. pass-by-value states that we should allocate a new location in the store for the record.
  2. However, the locations still refer to the original locations.

Behaviour when properties reassigned

a = {'a': 1}

function f(o) {
  o.a = 2;
}

f(a)
a // {'a': 2}

Behaviour when object reassigned

a = {'a': 1}

function f(o) {
  a = 2; // different location instantiated for a, original a is not modified.
}

f(a)
a // {'a': 1}
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