Call by name, by refrence, by need and by value

Question

void main()
{
    int i = 10, j = 20;
    evaluate(i+j);
}
void evaluate(int x)
{
    print(x);
    x = 2 * 10; // in this I think call-by-name give lvalue error.
    print(x);
}

I think call-by-reference will also give an error, because call-by-reference needs an address to point.

Evaluate the result using

1. call-by-reference

2. call-by-name

3. call-by-need

4. call-by-value.

Comments

about 'call by name' name goes mean i+j goes to x and it would be like i+j=2*10  so i don't think it would generate error.

I think it will generate "lvalue required" error because i+j result an rvalue not lvalue.

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sorry shubhanshu , i went wrong

lvalue error certainly because we are assigning in an expression.

yes! i can edit , but first you tell your goal. Then only i would be able to edit.

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Goal -> Just to understand, the basis of all four? which include any expression as it is different than passing directly variables.

Answer 1

Call by reference :- Here at calling time addresses of variables are passes and as we work here on address(logical address) of variable , any change done to the value on this address is at the moment functionalized.

Call by value result(copy restore or copy reference) :- it's special case of call by reference. o/p of call by value result is almost always same as call by reference except few cases(i mentioned those in my examples).Actually when we send ame argument twice (aliasing)under call by reference , writing to one will affect other but under call by copy restore , it wont happen.

Call by name :-Here just substitute formal parameter with actual parameter , where ever they appeared in called function.

i am attaching link , where you will get some solved questions for above three calling techniques.If you have any doubt , just comment.

Another thing is by default C/C++ support call by value, for call by reference , we have to manually pass the address(like we do using & and *).

https://drive.google.com/open?id=1Stfy-Q6AltW4uDMe-QFmcOAqkfBKDK6g

https://en.wikipedia.org/wiki/Evaluation_strategy#Call_by_copy-restore

http://www.lix.polytechnique.fr/~catuscia/teaching/cg428/02Spring/lecture_notes/L07.1.html

https://courses.cs.washington.edu/courses/cse505/99au/imperative/parameters.html