boost::optional and its internals
Posted on: 04/12/2009
- In: boost
- 11 Comments
boost::optional is a very handy generalization of returning a null when there’s nothing to return. Consider a function such as strstr – either the required sub-string is found within the given string, in which case a pointer to it is returned, or a NULL value is returned to indicate that there was no such sub-string. In terms of boost::optional we would either return the same pointer to the occurrence of that sub-string (as before), or we would simply return nothing – no value at all. In this post we will demonstrate the usage of boost::optional and discuss its implementation.
If you ever try to define a public custom operator new while keeping the corresponding delete operator private, you’ll end up unable to compile any code that actually invokes the public operator new. The reasoning is quite interesting.
Suppose you wanted to check the size (in bytes) of a certain type, WITHOUT using the sizeof() operator. How would you do that?
And what is the size of an empty struct (or class), anyway?
ScopeLogger
Posted on: 18/11/2009
- In: snippets
- 13 Comments
The RAII design pattern can be utilized to create simple and intuitive logging facilities, like the one we will present now. Through the useful macro LOG_FUNC, the proposed ScopeLogger will easily create function call graphs at run time, to allow easy debugging and tracking of program execution.
Enumerating permutations
Posted on: 14/11/2009
- In: algorithms
- 5 Comments
There are exactly n! different permutations of n numbers. This challenge was about writing a function which is able to enumerate all these permutations, i.e. function permute(n, idx) which is able to return permutation with index idx of n numbers. The requirement is ofcourse that all these permutations must be unique – this is in order to go over all possible permutations.
The State design pattern is a very useful design pattern. In this article we will exploit it to provide a very slick and elegant implementation of a Finite State Machine (FSM).
First of all, a FSM consists of a finitie number of states and a predefined set of rules defining the transitions between all these states. Each state can either ACCEPT or REJECT the input – the FSM accepts the input IFF it ends up on an accepting state at the end of execution. In our design, each state will be modeled by a distinct class derived from an abstract base State class. Each state class will also contain all of its relevant transition logic. This architecture will enable us to provide a very flexibe, powerful, yet intuitive and simple, implementation of any FSM.
Reset an array in constant time
Posted on: 05/11/2009
Ever wondered how to reset an entire array of N elements in a constant slice of time? This post will introduce the algorithm along with an implementation.
Let me lay out the problem. There’s an array of N integers. We would like to be able to reset that array (set all elements to zero), in a set amount of time – regardless of the value of N. The reset operation should take the same amount of time whether it operates on 100 elements or 10,000 of them.
cplusplus.co.il 
Recent comments