1. Example 1

2. def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a )

3. singthrice( x ) x
def singthrice( x ):
sing the value in x three times, loudly 2
def hop( y ):
hop y times
main()
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a )

4. def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
main()
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a )
hop( y ) y 1

5. singthrice( x ) x
def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
154
main()
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a )

6. def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
main() a
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a ) -1

7. singthrice( x ) x
def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
main() a
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a ) -1

8. def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
main() a
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a ) -1
hop( y ) y 2

9. def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
main() a
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a ) 1

10. def singthrice( x ):
sing the value in x three times, loudly
def hop( y ):
hop y times
main() a
def main( ):
singthrice( 2 )
hop( 1 )
singthrice( 154 )
a=-1
singthrice( a ) #
#not a a a
hop( 2 )
a = 1
hop( a ) 1
hop( y ) y

11. Notes on Example 1 literals as arguments: 2, 154
variables as arguments: a
pass by value: argument to parameter
main's local variables: a
singThrice's local variables: x
hop's local variables: y
scope of local variables: only understood in function in which they are defined.

12. Example 2

13. def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')

14. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
" T"
def writeThisLetter( c ):
write the value of c
main()
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
output

15. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
" T"
def writeThisLetter( c ):
write the value of c
return "U"
main()
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
output

16. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
" T"
def writeThisLetter( c ):
write the value of c
return "U"
main() x
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
output

17. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
"R"
main() x
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
output

18. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
"R"
main() x
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
return "S"
output

19. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
"R"
main() x y
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
return "S"
"S"
output

20. def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
main() x y
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
"S"
output
GO SU!

21. def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
main() x y
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
"S"
output
GO SU!
USA

22. def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
main() x y
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
writeThisLetter(c) c
"S"
"B"
output
GO SU!
USA

23. def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
main() x y
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
writeThisLetter(c) c
"S"
output
GO SU!
USA
"U"

24. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
main() x y
"G"
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
"S"
output
GO SU!
USA

25. tellNextLetter(c) c
def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
main() x y
"G"
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+"!")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
return "H"
"S"
output
GO SU!
USA

26. def tellNextLettet( c ):
tell main the letter after the value of c
def writeThisLetter( c ):
write the value of c
main() x y
def main( ):
x=tellNextLetter('T')
y=tellNextLetter('R')
print("GO "+y+x+" !")
print(x+y+"A")
writeThisLetter('B')
writeThisLetter('U')
tellNextLetter('G')
writeThisLetter('S')
"U"
writeThisLetter(c) c
"S"
output
GO SU!
USA
"S"

27. Notes on Example 2 string literals as arguments : 'T' or "T"
return values may be stored in a variable and used: x=tellNextLetter('T')
or return values may be ignored: tellNextLetter('G')
scope of parameters