CODEWITHSUNDEEP
c#
Amin Saadati
Amin Saadati

Reputation: 133

I don't understand how this phrase is calculated in c#

I test this code 

int value = (char)+(int)-(float)+(double)-1;

and I get this result (1) that means value is 1! How is this calculated?

EDIT:

I had an interview yesterday in a company and this was their question, and I did not know how this number was obtained 1. So I am trying to understand how this result comes about.

Upvotes: 4

Views: 199

Answers (3)

Koby Douek
Koby Douek

Reputation: 16693

It's a matter of simple arithmetics:

(double)-1 is calculated to -1

(float)+(double)-1 is calculated to -1

(int)-(float)+(double)-1 is calculated to +1

(char)+(int)-(float)+(double)-1 is calculated to +1

Upvotes: 0

Giulio Caccin
Giulio Caccin

Reputation: 3052

The calls:

  • int value = (char)+(int)-(float)+(double)-1;
  • int value = (int)-(float)-1;
  • int value = 1;

Have the same Intermediate Language that push the number 1 into the evaluation stack:

IL_0000:  nop         
IL_0001:  ldc.i4.1    // <-- push to stack
IL_0002:  stloc.0     // value
IL_0003:  ldloc.0     // value
IL_0004:  call        LINQPad.Extensions.Dump<Int32>
IL_0009:  pop         
IL_000A:  ret

Optimization reduce your operation to a simple assigment.

Upvotes: 5

DavidG
DavidG

Reputation: 119146

This is really just a lot of casting. The + and - signs are only being used to negate the number. So take the first bit of the expression, that casts -1 to a double:

(double)-1

Then take the result of that and cast it to float:

(float)+(-1)

And so on until you end with a char that is implicitly cast to an int.

Upvotes: 8

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