Question

Give brief examples of different variable scoping using Haskell, Prolog, Java, C, JavaScript, and/or MIPS

Answer 1

/*------------------- Scope of variables in Java -------------------------*/

1. Member Variables (Class Level Scope) : These variables should be declared inside class but outside any member function/method . They can be directly accessed from anywhere in the class.

Example :

public class ScopeClassTest
{

int variable1;
private String variable2;
String function1() {}
float function2() {}
char c;
}

2. Local Variables (Method Level Scope) : These variables are declared inside a method/function and can’t be accessed outside the method.

Example :

public class ScopeMethodTest
{
void function1()
{
int localVar;
}
}

3. Loop Variables (Block Scope) : The variables declared inside pair of brackets “{” and “}” in a method has scope withing the brackets only.

public class BlockScopeTest
{
public static void main(String args[])
{
{
int y = 5550;
System.out.println(y);
}
}
}

/*----------------------Scope of variables in JavaScript --------------------------*/

1. Local Variable : Variables declared within a function. These variables can only be accessed from within the function.

Example :

function getHospitalName() {
var hospitalName = "ABC";

// Only here we can use this variable hospitalName

}

2. Global Variables : Variables which are declared outside a function, has global scope.

Example
var hospitalName = "ABC";

// code here can use hospitalName

function getHospitalName() {

// code here can also use hospitalName

}

/*----------------------Scope of variables in C --------------------------*/

1. Local Scope :

int main ()
{
int a,b,c; /* local variables */

a = 80;
b = 50;
c = a - b;

printf ("value of a = %d, b = %d and c = %d\n", a, b, c);

return 0;
}

2. Global Scope :

#include <stdio.h>

int c; /* global variable */

int main ()
{
int a,b; /* local variables */

a = 20;
b = 30;
c = a + b;

printf ("value of a = %d, b = %d and c = %d\n", a, b, c);

return 0;
}

/*----------------------Scope of variables in Haskell --------------------------*/

1. Global Scope :

a = 100

2. Local (Function) Scope :

multiply x = x * x

/*----------------------Scope of variables in Prolog --------------------------*/

Two uses of an identical name for a variable only refer to the same memory location if they are within a single clause.

good(X) :- old(X).
good(Y) :- wise(Y).

/*----------------------Scope of variables in MIPS --------------------------*/

data
globalVariable: .abc 20

.text

#access
lw $a0, globalVariable

#modify
la $a0, globalVariable #get address
li $a1, 11 #new value
sw $a1 0($a0) #save new value

lw $a2, globalVariable #get new value