=============
Call by Value [TOC]
=============

When you pass an argument to a function, the function receives a copy of the
argument. After the function call, the passed argument remains unchanged, even
if the called function modifies the received argument.

---- CODE(file=session03/page05/ex4.abc, type=abc, linenumbers) ----------------
@ <stdio.hdr>                                                                    
                                                                                 
fn foo(n: int)                                                                   
{                                                                                
    printf("foo entered: n = %d\n", n);                                          
    n = 42;                                                                      
    printf("foo leaving: n = %d\n", n);                                          
}                                                                                
                                                                                 
fn main()                                                                        
{                                                                                
    local n: int = 123;                                                          
                                                                                 
    printf("main: n = %d\n", n);                                                 
    printf("calling foo:\n");                                                    
    foo(n);                                                                      
    printf("returned from foo\n");                                               
    printf("main: n = %d\n", n);                                                 
}                                                                                
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Task
====

- Translate the program and execute it. Go through the program line by line
  again to understand which output is generated in which line. Confirm the
  claim that a function only receives a copy (and not the original) of the
  argument. On my computer, I get the following output:

  ---- SHELL (path=session03/page05) -------------------------------------------
  abc ex4.abc
  ./a.out
  ------------------------------------------------------------------------------

- To clarify that the caller of a function can name the argument differently
  than the callee, make the following change: Rename the local variable in
  function main to `x`.