Question

Consider the following code:

int a:=10   //global
int b:=12   //global
proc F  
  a:= a-b
proc P (M:proc)  
    int a:=2 
    M()
proc K 
    int b:=3   
    P(F)
K()                  //main program
print(a)          //built in function

 

a- what does this code print if it uses dynamic scoping and deep binding?

b- what does this code print if it uses dynamic scoping and shallow binding?

Answer 1

Solution:

Let's have a definition of deep binding and shallow binding first.

Deep binding:

Deep binding captures the environment at the point. and it takes the environment of the parent function.

Shallow binding:

Shallow binding takes the environment of the final calling function.

a)

int a:=10   //global
int b:=12   //global
proc F  
  a:= a-b
proc P (M:proc)  
    int a:=2 
    M()
proc K 
    int b:=3   
    P(F)
K()                  //main program
print(a)          //built in function

main method is where K() is called Now in the K method body b of int type is defined and initialized with the value 3.

Now F is called now a=a-b, here the value of a and b will be called from parent function which means the global value of a and b which is 10 and 12 respectively. now a= -2.

now the control is back to the main an print(a) will print -2.

b)

Here also

main method is where K() is called Now in the K method body b of int type is defined and initialized with the value 3.

Now F is called now a=a-b, here the value of a and b will be called from the function which called the function where we are at; this means the value of b will be taken from the calling function which is 3 and the value of a will be taken from the global value which is 10 now a= 7

now the control is back to the main an print(a) will print 7.

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