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\\" % x[ 0 ] )

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