Return from Constructor Body

When Python reaches the end of the constructor body, set the return value to the reference to "self." More formally,

For example, suppose that the following are true:

• the line at time 37 = 6
• the tab at time 37 = 2
• statement at line 6, tab 1 = def age_in_months(self):
• Control Map at time 37 = [ entry 0: (pair ("class", "Person")), [ entry 1: (pair ("method", "__init__")), [ ] ] ]
• Variables Map at time 37 = [ entry self: (Python reference 0), [ entry first_name: "John", [ entry last_name: "Smith", [ entry age: 25, [ ] ] ] ] ]

Here is the "Variables" map in table form:

Name	Value
self	py_ref(0)
first_name	"John"
last_name	"Smith"
age	25

We know that 1 < 2. Also, we can see that:

value at (2 - 1) in map (Control Map at time 37) = pair ("method", "__init__")

Therefore, we can conclude that:

Return Value at time (37 + 1) = value at self in map (Variables Map at time 37)

Since:

value at self in map [ entry self: (Python reference 0), [ entry first_name: "John", [ entry last_name: "Smith", [ entry age: 25, [ ] ] ] ] ] = Python reference 0

We claim that:

value at self in map (Variables Map at time 37) = Python reference 0

Thus, we conclude that:

Return Value at time (37 + 1) = [ Python reference 0, [ ] ]

Which simplifies to:

Return Value at time 38 = [ Python reference 0, [ ] ]

See here for the full proof.

Try stepping through the simulator to see LW Python push reference 0 to the Return Value

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