I have to use borland TurboC++ for C programming in my college.
They say our examination board recommends it. I have to use it..
The problem is that they gave this operator precedence related question:
int a=10,b=20,result;
result1 = ++a + b-- - a++ * b++ + a * ++b;
printf("result=%d",);
printf("\n a=%d",a);
printf("\n b=%d",b);
Other compilers like gcc can't perform this operation. But turbo C can and gives us:
result=32
a=12
b=21
I made mistake in my test. My teacher tried to explain what's going on. But I am not convinced. Is it some kind of weird behavior of turbo C or in older days it used to be totally fine with all compilers. If so, what are the steps to understand what is going on and how to understand.
To solve these kind of problem, turbo-c do it in manner as follows :
1) Consider the initial value of variables used.
a=10
b=20
2) Count all the pre-increment and decrements for each variable and store all post on stack separate for each variable.
for variable a
pre increment = 1 therefore change the value of a to 11
post = 1 stored to stack
for variable b
pre increment = 1 therefore change the value of b to 21
post = 2 stored to stack
3) Now replace all the pre and post with the current value of a and b
result = 11 + 21 - 11 * 21 + 11 * 21 ;
result = 11 + 21;
result = 32;
4) lastly pop the stack and perform the operation on the variable.
a = 12
b = 21
This the only way to solve this problem. You can check the procedure with any question of same kind. The result will came out same. g++ fails to solve because it probably cannot resolve the variable in the same way thus the precedence error came in picture. It might probably fail with ++ + and -- - because it cannot understand the increment or decrements operator and forms ambiguous trees.