advantage of bool?

[madhav92]

I just started learning c++ and i came across the built in data types and i am not able to understand what exactly is the advantage of having a bool data type, some one please help me

[abhishekm71]

bool is a very important data type that has only two possible states, true (or non-zero) or false (or 0).

It is widely used in conditional 'if' statements and for, while loops.

if ( some Boolean expression is true) { 
//   do something. This executes if the above Boolean expression evaluates to true.
}

while ( ! (some Boolean variable) ) {

   // Keep doing this. These statements are repeatedly executed until the above Boolean
  // variable becomes false.
}

Moreover, there can be functions that return bool datatype, to be used in further conditional statements.

EDIT: bool true corrected.

[rodiongork]

Historically C and C++ allow use of int for conditional expressions. I suppose that is why the question is asked.

Using bool instead of int will not change program significantly, however it is considered improving readability, maintainability etc.

[S6k9GNh0]

It might also be an optimization as far as memory size and operations concerning booleans.

I would look into masks as well.

[Stewbond]

Just a minor correction. false is 0 and true is not-zero. When you cast a bool to an int, this is converted to 1. However this statement is also true:

int i = 2;
if (i == true) 

[abhishekm71]

@Stewbond, Thanks for pointing out.

Corrected.

[madhav92]

Ok so bool converts all non zero integers to true and zero to false right?
so is this valid?
bool b=-4;
if (bool)
std::cout<<"hi";

[abhishekm71]

You mean if ( b ).

Yes the cout statement shall execute.

[Hzj jie]

all the numeric data types can be transformed to bool implicitly, following the rule 0 == false, others == true, which cause the trouble of

int a = 20;
int b = 30;
if(a = b) {}
if(a == b) {}

i do not think this is an advantage in c++, but it's the legacy problem. and usually someone will tell you to write like,

if(20 == a) {}

to avoid such trouble.

but pay attention to vector<bool>, it's a specialization of vector template, which uses 1 bit, 1 == true, 0 == false. this can help to save memory, but the trouble is,

vector<bool> vb;
for(int i = 0; i < 100; i++) vb.push_back(true);
bool& t = vb[0];

which is wrong.

[madhav92]

Sorry Abhishek tat was my mistake , i jus started learning yesterday so little confusion and thanks to everyone ,now i am clear about using the data type bool, and can someone give me an easy example to explain polymorphism?

[ne555]

@Stewbond: please cut your left hand

> However this statement is also true:
¿which statement?