adding booleans (as integer)

Question

I wrote a code in AS3 which allowed me to check if a particular number of things were true...

If (true + false + true + true + false + true + true < 4)
{

}

When i tried rewriting in C#, it tells me i cannot add type bool and bool. Is the best way of doing this to rewrite it like this? Or is there some simpler work around?

If ((true?1:0) + (false?1:0) + (true?1:0) + (true?1:0) + (false?1:0) + (true?1:0) + (true?1:0) < 4)
{

}

http://stackoverflow.com/questions/377990/elegantly-determine-if-more-than-one-boolean-is-true — Joel Purra, Sep 11 '12 at 11:45

Joel Purra · Accepted Answer · 2016-09-15T14:31:36.357

66

Try using IEnumerable<T>.Count(Func<T,bool>) from System.Linq, with T as bool, on a params method parameter.

public static int CountTrue(params bool[] args)
{
   return args.Count(t => t);
}

Usage

// The count will be 3
int count = CountTrue(false, true, false, true, true);

You can also introduce a this extension method:

public static int TrueCount(this bool[] array)
{
   return array.Count(t => t);
}

Usage

// The count will be 3
int count = new bool[] { false, true, false, true, true }.TrueCount();

edited Sep 15 '16 at 14:31

answered Sep 07 '12 at 11:23

Joel Purra

24,294
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1

Nice one! Very clean and elegant code! – Mithrandir Sep 07 '12 at 11:25
1

That's beautiful :') Thanks, this is just what i'll use! – Joel Sep 07 '12 at 11:33
3

+1 Yeah, nice idea using `params` – sloth Sep 07 '12 at 11:35

score 17 · Answer 2 · answered Sep 07 '12 at 11:23

17

You could create an array and use Count:

if ((new []{true, false, true, true, false, true, true}).Count(x=>x) < 4)
{

}

or the Sum method:

if ((new []{true, false, true, true, false, true, true}).Sum(x=>x?1:0) < 4)
{

}

answered Sep 07 '12 at 11:23

sloth

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If i were using it as a one off, this is how i'd do it, thanks heaps for replying *upvotes* – Joel Sep 07 '12 at 11:36
1

Thanks! This was my favorite approach. I had a few bools I needed to add like this, and (new[] {var1, var2, var3, var4}).Sum(x => x ? 1 : 0); worked great for me! – Stachu Oct 02 '13 at 15:32

score 13 · Answer 3 · answered Sep 07 '12 at 11:33

Here's a more fun example:

if ((BoolCount)true + false + true + true + false + true + true <= 5)
{
    Console.WriteLine("yay");
}

Using this class:

struct BoolCount
{
    private readonly int c;
    private BoolCount(int c) { this.c = c; }

    public static implicit operator BoolCount(bool b)
        { return new BoolCount(Convert.ToInt32(b)); }

    public static implicit operator int(BoolCount me)
        { return me.c; }

    public static BoolCount operator +(BoolCount me, BoolCount other)
        { return new BoolCount(me.c + other.c); }
}

score 5 · Answer 4 · answered Sep 07 '12 at 11:25

5

Convert.ToInt32(true) + Convert.ToInt32(false) + Convert.ToInt32(true) also work in this case i think this is simplest way we have

answered Sep 07 '12 at 11:25

Gyan Chandra Srivastava

1,370
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score 0 · Answer 5 · answered Sep 07 '12 at 13:07

You could write an extension method for the BitArray class. I'm not sure if the performance would be any better than using Linq, but at least its another option:

public static int CountSetBits(this BitArray theBitArray)
{
   int count = 0;
   for (int i = 0; i < theBitArray.Count; i++)
   {
      count += (theBitArray.Get(i)) ? 1 : 0;
   }
   return count; 
}

Usage:

BitArray barray = new BitArray(new [] { true, true, false, true });
int count = barray.CountSetBits(); // Will return 3

score -1 · Answer 6 · answered Sep 07 '12 at 11:33

(Inspired by L.B.:s comment) you could write an extension method:

static class Ex
{
    public static int Int(this bool x) { return x ? 1 : 0; }
}

And then (provided you include a using to the namespace containing the Ex class), you can write your if statement like this:

if (true.Int() + false.Int() + true.Int() + true.Int() + 
    false.Int() + true.Int() + true.Int() < 4)
{
    ...
}

adding booleans (as integer)

6 Answers6