What is absolute value of Integer.MIN_VALUE ?

what does below code return?

[java]
int ret = Math.abs(Integer.MIN_VALUE);
[/java]

In the number system, there are more negative numbers than positive ones. Not all -ve numbers have their positive counterparts (e.g. -3 & +3). Ignoring 0. The minimum possible number in 32 bit number is 10000000000000000000000000000000(31 zeroes, say 1000...0).

Here is how absolute value is calculated.

we take Two's compliment by inverting the whole number (replace 1 with 0 and 0 with 1) and then add 1 to the final value.

Lets do it together:

in 2*32 bit number... 1000...0 is -ve

1) 2s compliment would be:

~100000...0 = 011111...1

2) add 1, would become 01111...11 + 1 = 1000000...0

so its back to the same number Integer.MIN_VALUE

Absolute value of MIN_VALUE is itself.

[java]
Integer.MIN_VALUE = Math.abs(Integer.MIN_VALUE)
[/java]

Note: Math.abs(...) doesn't guarantee to always return positive number. The same is true for "%" operator as it gives remainder but not modulo. Remainder could be negative.

CPP Header Files

The standard practice is to have one header file (.h) per class file (.cpp). The correct use of the header files could enhance the readability and also boost the performance of the code. When deciding which portion of code to put where , think about the Locality of Reference first because this matters as well.

Below are the few points to remember while designing the header files:

1. Header file guard

All header files should be guarded well to avoid multiple inclusions in the code. e.g.

[cpp]

#ifndef MY_SAMPLE_HEADER_H

#define MY_SAMPLE_HEADER_H

//contents of the header file here...

#endif

[/cpp]

2. Header file depedencies

Any file including the header files needed to be recompiled whenever the contents in the header file changes. This leads to big dependency in the compile time. In the scenarios where including header file is not needed, forward declaring the class should be more than enough. Doing this will help not recompile the class however the symbol will be resolved at the linking phase of the compilation process.

3. Inline methods

Inline methods are defined in side the class declaration body itself i.e. in .h file instead of the .cpp file. Inlining methods which are about 10 lines big lead to better program performance.

4. Method parameter and Include file ordering

The general convention to order the parameters in the methods are input first and then output parameters. Remember that all inputs should be declared "const <data type> &_data" so that method can't modify the _data.
The output parameters are generally declared non-constant "<data_type> &_data".

The order of the header file included should be done in the order of their path names. This doesn't made any difference in the performance of the program however it improves the readability of the code.

5. Header comment

Header comments give the glimpse of what is file about and how the code has evolved since its first version.

a sample of the comment is here:

[cpp]
/* ---------------------------------------------------------------------------
**
** <filename>.h
** Description:<very brief file description>
**
** Author: <original author>
** Change History
** 1.0 - changed the accessors to inline
** -------------------------------------------------------------------------*/
[/cpp]