If statement in C++ and its C# conversion

Question

3.00/5 (2 votes)

See more:

Hi
What does this statement in c++ mean:

if (!(someVariable%20))

Is this is the meaning in C#:

if (someVariable % 20 != 0)

Thanks

Posted 15-May-12 8:15am

Member 8456258

Updated 15-May-12 8:31am

v2

Add a Solution

Comments

Sandeep Mewara 15-May-12 14:24pm

Is the first line valid? AFAIK, below line should be valid in C++ too. Lets see what others say.

lewax00 15-May-12 14:54pm

It is valid, it's just shorthand for checking if something is equal to 0.

Sandeep Mewara 15-May-12 15:09pm

Ok. Thanks. Good to know these small things while browsing questions.

:thumbsup:

Member 8456258 15-May-12 14:29pm

Yes, the first line is a functional code and it runs fine.

JackDingler 15-May-12 14:50pm

And depends on operator precedence in C#.

Could be equivalent to:
if ((someVariable % 20) != 0)
or
if (someVariable % (20 != 0))

I would guess it's the first one, but for such things, I use parenthesis to demonstrate my clear intent.

lewax00 15-May-12 14:52pm

The first. Boolean comparison operators (<, >, ==, etc.) are applied later in most languages (C# included).

Sandeep Mewara 15-May-12 15:13pm

5 as I learnt something from this one.

4 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Maciej Los · Accepted Answer · 2012-05-15T08:39:00

Solution 1

C and C++ operators[^]
C# operators[^]

In both languages % means modulo[^], so both conditions checks for the remainder of division of one number (variable) by another (20).

Posted 15-May-12 8:39am

Maciej Los

Comments

Member 8456258 15-May-12 14:45pm

I understand, but are they the same? I mean does (!(someVariable%20)) statement in c++ return true when the division of someVariable to 20 results in 0? by the way someVariable increments. So, if my assumption is correct does it mean that the operation suppose to happen once every 20 times of iteration?
Thanks.

lewax00 15-May-12 15:00pm

Yes, that assumption is correct.

Sergey Alexandrovich Kryukov 15-May-12 18:30pm

Right, a 5.
--SA

Maciej Los 16-May-12 0:36am

Thank you ;)

VJ Reddy 16-May-12 7:21am

My 5!

Maciej Los 16-May-12 7:30am

Thank you ;)

Clifford Nelson · Accepted Answer · 2012-05-15T08:45:00

Solution 2

Yes it does. You can also express this in C# as

if (! Convert.ToBoolean(i % 20))

C# does not automatically convert 0 to false like C++

Posted 15-May-12 8:45am

Clifford Nelson

Comments

Member 8456258 15-May-12 15:12pm

I like this one, thanks!

Maciej Los 15-May-12 16:24pm

Good answer, my 5!

Sergey Alexandrovich Kryukov 15-May-12 18:34pm

I would avoid it. Additional call, and what for? Just to reduce readability and add a chance of a mistake?
if (someVariable % 20 == 0) is the best.
--SA

Clifford Nelson 15-May-12 20:14pm

I was not advocating using it, just showing that it was the same.

OriginalGriff · Accepted Answer · 2012-05-15T08:50:00

Solution 4

No. the two are not the same: the !someVariable%20 does an logical invert on somevariable first, then takes the value modulus 20. If that is non-zero, it's true. Try it:

C#

int someVariable;
for (someVariable = 0; someVariable < 21; someVariable++)
   {
   Console::WriteLine(L"");
   if (!someVariable%20) Console::WriteLine(L"YES");
   else Console::WriteLine(L"NO");
   if (someVariable%20 != 0) Console::WriteLine(L"YES");
   else Console::WriteLine(L"NO");
   }

You get:

YES
NO

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
YES

NO
NO

Posted 15-May-12 8:50am

OriginalGriff

Comments

lewax00 15-May-12 14:55pm

Except there are parenthesis, so the inversion is applied last.

OriginalGriff 15-May-12 14:57pm

They weren't there when I looked! I'm sure I copy and pasted it into my app to test it... :confused:

Member 8456258 15-May-12 15:19pm

You are right I missed the parenthesis at first but later I updated the question. I apologize for that but your answers were very useful, thanks!

OriginalGriff 15-May-12 15:24pm

:laugh:
Probably my fault for answering the phone in mid typing!

lewax00 · Accepted Answer · 2012-05-15T08:49:00

Solution 3

The code checks if someVariable is evenly divisible by 20: someVariable%20 returns the remainder of someVariable/20, if the remainder is 0 it is evenly divisible, and in C++ !0 is true.

For C# if the original C++ line doesn't work, then what you want is

C#

if (someVariable % 20 == 0)

Posted 15-May-12 8:49am

lewax00

Comments

Maciej Los 15-May-12 16:24pm

Good answer, my 5!

Sergey Alexandrovich Kryukov 15-May-12 18:33pm

This is a correct way. I would advise to avoid implicit Boolean conversion allowed in C++.
My 5.
--SA