CODEWITHSUNDEEP
cif-statement
Aaron_Actu
Aaron_Actu

Reputation: 112

Is else...if statement in C equals to else { if }?

My question:

Is this:

if (...) {
  
} else if (...) {
  
}

Equal to this?

if (...) {
  
} else {
  if (...) {
    
  }
}

Indeed, I guess that in the two cases the result would be the same but is else..if a different statement in C ?

Upvotes: 3

Views: 190

Answers (5)

Boxman07
Boxman07

Reputation: 13

If you write

    if(...){
    } else{ 
        if(...){ ... }
    }

That would be the same as

if (...) {
  
} else if (...) {
  
}

As long as you keep the else statement empty except for the second if statement.

else if isn't technically its own statement. else if is literally an else statement and then an if statement.

Upvotes: 0

Eric Postpischil
Eric Postpischil

Reputation: 222526

They are almost the same thing.

They are the same as a compiler would treat them exactly as they stand now.

However, they are not the same for development purposes. If additional code is inserted immediately after the end of the enclosed if statement, it will be grouped with that statement in the code with the braces around that if statement but not in the code without those braces. Issues like this are potential causes of bugs, so the difference may be significant.

Upvotes: 0

Tony Tannous
Tony Tannous

Reputation: 14876

To address the comments suggesting drawing truth table, logically equivalent programs aren't always the same in terms of the generated assembly (they will behave the same) but consider:

int main()
{ 
    int a = 1;
    if (a)
       if(a)
          return 0;
}

And

int main()
{ 
    int a = 1;
    if(a)
      return 0;
}

Compiling with no optimization -O0

main:
        push    rbp
        mov     rbp, rsp
        mov     DWORD PTR [rbp-4], 1
        cmp     DWORD PTR [rbp-4], 0
        je      .L2
        cmp     DWORD PTR [rbp-4], 0
        je      .L2
        mov     eax, 0
        jmp     .L3
.L2:
        mov     eax, 0
.L3:
        pop     rbp
        ret

main:
        push    rbp
        mov     rbp, rsp
        mov     DWORD PTR [rbp-4], 1
        cmp     DWORD PTR [rbp-4], 0
        je      .L2
        mov     eax, 0
        jmp     .L3
.L2:
        mov     eax, 0
.L3:
        pop     rbp
        ret

https://godbolt.org/z/4ajevq

Upvotes: 0

Lundin
Lundin

Reputation: 213711

The C language has no feature called else if. That one is only obtained through coding style. Your example is 100% equivalent to this:

if (...) {
  
} 
else 
  if (...) {
  
  }

Where the second if is a single statement below else, so we can write it without {}.

Upvotes: 2

kiran Biradar
kiran Biradar

Reputation: 12732

if (...) {
  
} else if (...) {
  
}

is same as

if (...) {
  
} else {
  if (...) {
    
  }
}

but

if (...) {
  
} else if (...) {
  
}

is not same as

if (...) {
  
} else {
   ... // extra statements
  if (...) {
    
  }
}

Upvotes: 2

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