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Memory Model

Table of contents

1. Variable Assignment

<<variable>> = <<expression>>

  • Step 1:
    Evaluate the expression to produce a value. This value is stored in a memory object.
  • Step 2:
    Store the address of the memory object in the variable.
    (If the variable already exists, replace the memory address that is contains.)
  • Result:
    The variable points the memory where the value is stored.
    implementation : A (proper) namespace(dict) has the pair of the key variable(str) and the value value(object).

example

input :

f = min
f = max
g, h = min, max
max = g
max(f(2, g(h(1, 5), 3)), 4)

step-by-step:

[0] min in built-in namespace → <function min>
[0] max in built-in namespace → <function max>

[1] f in global namespace → <function min>(evaluation of min)
[2] f in global namespace → <function max>(evaluation of max)
[3] g in global namespace → <function min>(evaluation of min)
[3] h in global namespace → <function max>(evaluation of max)
[4] max in global namespace → <function min> (evaluation of g)
[5] min(max(2, min(max(1, 5), 3)), 4)
[5] Return value in local(<function min>) namespace → 3

output :

3

2. Function Call

myfunc(arg1, agr2, ...)

  • Step 1:
    Evaluate the arguments left to right.
  • Step 2:
    Create a namespace to hold the function call’s local variables, including the parameters.
  • Step 3:
    Pass the resulting argument values into the fuction by assigning them to the parameters.
  • Step 4:
    Execute the function body. When a return statement is executed, the function terminates and the value of the expression in the return statement is used as the value of the function call.