GATE1995-1.4

Question

In the following Pascal program segment, what is the value of X after the execution of the program segment?

X := -10; Y := 20;
If X > Y then if X < 0 then X := abs(X) else X := 2*X;

• A. $10$
• B. $-20$
• C. $-10$
• D. None

Answer 1

Answer of $X$ remains unchanged. As the if condition becomes false.

X := -10

Answer is C . This is classic example of $if-else$ issue. Always $else$ matches for nesting to the closest $if$  in $C$ Programming & Pascal .
https://en.wikipedia.org/wiki/Dangling_else

if (x>y)
{
   if (x<0)
       x=abs(x)
    else
       x=2*x
}

Comments

else matches to closest if in all languages?

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For sure in C & Pascal ! We don't get any other languages in GATE !

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But here x < y i.e.  -10 < 20

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Yes you seem correct. Updated.

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When having confusion, always try to match else with last unmatched if condition.

This is usually the solution the compiler follows for dangling else problem during compilation of a program.

Reference: Ullman for compilers

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@Ayush Upadhyaya

I havenot got your point

always try to match else with last unmatched if condition.
 

means?

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Means

if(a>b) then if(b>c) then t=x else v=y will be

if(a>b) then

      if(b>c) then

          t=x

      else

      v=y