Check severeal boolean returns in same time

Question

I have several bool elements and I am checking it if returns me false.

bool i = false;
        switch (idcount)
        {
            case 1: i = p1(); break;
            case 2: i = p1() & p2(); break;
            case 3: i = p1() & p2() & p3(); break;
            case 4: i = p1() & p2() & p3() & p4(); break;
            case 5: i = p1() & p2() & p3() & p4() & p5(); break;
            case 6: i = p1() & p2() & p3() & p4() & p5() & p6(); break;
            case 7: i = p1() & p2() & p3() & p4() & p5() & p6() & p7(); break;
            }
return i;

I want if one of p*() returns false in any case i returns false. Is it right way or two false returns true? I want all p*() return true i returns true..

Answer 1

use && (logical and) not & (binary operator)

like:

p1() && p2();

it will return true only if all p*() are true (same as &), but note that if first p*() will return false rest of expression won't be evaluated. In case of & whole expression will be evaluated

var functions = new List<Func<bool>>();
functions.Add(p1);
functions.Add(p2);
functions.Add(p3);
functions.Add(p4);
functions.Add(p5);
functions.Add(p6);
functions.Add(p7);
return functions.Take(idcount).All(x=>x());

try above it looks cleaner than switch statement and should examine if all first idcount entries are true same as switch case with &&

Answer 2

Of course your code should work as what you want, however I would like to use the following compact code:

List<Func<bool>> ps = new List<Func<bool>>();
ps.Add(p1);
ps.Add(p2);
ps.Add(p3);
ps.Add(p4);
ps.Add(p5);
ps.Add(p6);
ps.Add(p7);
var i = ps.Take(idcount).All(a=>a());

To use a normal for loop, you can do something like this:

var i = true;  
if(ps.Count >= idcount){
  for(int i = 0; i < idcount; i++){
    if(!ps[i]()) { i = false; break;}
  } 
} //else ???

Answer 3

Using & bit wise operator will cause all the expression to be evaluated even if you get the false in first p1(). You should use && logical operator to combine the condition.

Binary & operators are predefined for the integral types and bool. For integral types, & computes the logical bitwise AND of its operands. For bool operands, & computes the logical AND of its operands; that is, the result is true if and only if both its operands are true. The & operator evaluates both operators regardless of the first one's value, MSDN.

Conditional-AND operator (&&) performs a logical-AND of its bool operands, but only evaluates its second operand if necessary, MSDN.

Answer 4

You should be using && which is operator for logical (true/false) values.

i = p1() && p2();

& is a bitwise AND operator for numbers.

Answer 5

Considering the invariant you've stated

I want if one of p*() returns false in any case i returns false. Is it right way or two false returns true? I want all p*() return true i returns true..

your code is correct.

By using '&' you'll evaluate all functions. For Instance

case 5: i = p1() & p2() & p3() & p4() & p5(); break;

here if p2() returns false, i will still be false but p3, p4 and p5 will be avaluated(which may not be what you want). If you don't want that extra evaluation use the short circuit operator - && instead.

Answer 6

var areAllTrue = p1() && p2() && ... && p7();
return areAllTrue;

This will evaluate to true only if each p*() returns true.