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library.sol

pragma solidity ^0.4.0;

// using Libraries

library IntExtended {
    function Increment(uint self) returns (uint) {
        return self + 1;
    }
    
    function Decrement(uint _self) returns (uint) {
        return _self - 1;
    }
    
    function IncrementByValue(uint _self, uint _value) returns (uint) {
        return _self + _value;
    }
    
    function DecrementByValue(uint _self, uint _value) returns (uint) {
        return _self - _value;
    }
}

testLibrary.sol

pragma solidity ^0.4.0;

import "browser/library.sol";
// can also import from github
//import "github.com/jigar/solidity/library.sol"

contract TestLibrary {
    // can also use
    // using IntExtended for *;
    // * will work for all types including string
    using IntExtended for uint;
    
    function testIncrement(uint _base) returns (uint) {
        // Can also use static calling
        return IntExtended.Increment(_base);
        // return _base.Increment();
    }
    
    function testDecrement(uint _base) returns (uint) {
        return _base.Decrement();
    }
    
    function testIncrementByValue(uint _base, uint _value) returns (uint) {
        return _base.IncrementByValue(_value);
    }
    
    function testDecrementByValue(uint _base, uint _value) returns (uint) {
        return _base.DecrementByValue(_value);
    }
}