Question

Write a program, using the syntax of whatever language you like, that produces different behavior depending on whether pass-by-reference or pass-by-value-result is used in its parameter passing.

Answer 1

```
#!/usr/local/bin/python3
 

def add2x( x ):
    print( "beginning of add2x, x = %d" % x )
    x += 1
    print( "end of add2x, x = %d" % x )

def add2y( y ):
    print( "beginning of add2y, y = %d" % y[ 0 ] )
    y[ 0 ] += 1
    print( "end of add2y, y = %d" % y[ 0 ] )

if( __name__ == "__main__" ):
    x = [ 5 ]
    y = [ 5 ]

    print( "before add2x, x = %d" % x[ 0 ] )
    add2x( x[ 0 ] )
    print( "after add2x, x = %d\n" % x[ 0 ] )

    print( "before add2y, y = %d" % y[ 0 ] )
    add2y( y )
    print( "after add2y, y = %d" % y[ 0 ] )
```