Dr. Dobb's C/C++ Blogs

Abstractions For Binary Search, Part 10: Putting It All Together

Mon, 22 Dec 2014 07:24:00 -0500

After the discussions of the last few weeks, we are finally ready to build our test cases.

Abstractions For Binary Search, Part 9: What Do We Need to Test?

Tue, 16 Dec 2014 01:52:00 -0500

Many people confuse the idea of a test case working correctly with the idea of a program producing correct output.

Abstractions for Binary Search, Part 8: What Does It Mean To Say "It Works?"

Tue, 09 Dec 2014 09:20:00 -0500

Last week, we talked in general terms about how to test a binary-search function. Now let's get specific.

Abstractions For Binary Search, Part 7: Choosing Test Cases

Wed, 03 Dec 2014 22:15:00 -0500

Binary search is a particularly instructive algorithm to figure out how to test.

Abstractions For Binary Search, Part 6: How On Earth Do You Test It?

Mon, 24 Nov 2014 09:22:00 -0500

We will reduce a substantial part of our problem to calling these two functions repeatedly with suitably chosen test cases and verifying that they return the same results.

Abstractions For Binary Search, Part 5: Getting Down to Details

Thu, 13 Nov 2014 07:44:00 -0500

It's hard to imagine how this code could be much simpler. However, we don't actually know whether it works.

Invariants for Binary Search, Part 4: Using The Improved Abstractions

Mon, 10 Nov 2014 07:53:00 -0500

We continue our discussion of how to implement our binary search in an n-element sequence.

Sharper Than a Blue Tooth

Mon, 03 Nov 2014 17:20:00 -0500

This simple project sends out beacon data using the board's onboard temperature sensor (granted, it measures the internal chip temperature, which might not be that useful).

Invariants for Binary Search, Part 3: Improving Our Abstractions

Fri, 31 Oct 2014 07:15:00 -0400

With this abstraction under our belts, we can proceed to write code. If you're interested, you might like to do so for yourself before I show you the details next week.

Invariants for Binary Search, Part 2: Refining The Specifications

Wed, 22 Oct 2014 17:11:00 -0400

This week, we will try to define more carefully the problem we would like to solve before leaping into the solution.

Invariants For Binary Search, Part 1: A Simple Example

Thu, 16 Oct 2014 11:17:00 -0400

We can use an invariant to help us reason about a piece of code that many programmers find hard to get right by any other means.

Loop Invariants And Testing: Often Possible, Often Difficult

Mon, 06 Oct 2014 10:56:00 -0400

We can think of an invariant as being a claim or belief about the state of program that we expect to be true each time control reaches a particular point in the program.

A Loop Invariant Can Be An Optimization Tool

Mon, 29 Sep 2014 19:14:00 -0400

This week, we'll look at the helpful qualities of loop invariants.

Using a Loop Invariant to Help Think About a Program

Fri, 19 Sep 2014 13:51:00 -0400

Last week, I talked about how to write a loop invariant. I would like to continue this discussion by paraphrasing a beautifully elegant example that Dijkstra used in A Discipline of Programming.

Setting Up a Test Environment for C++14

Wed, 17 Sep 2014 13:11:00 -0400

A little clever work and I was able to quickly set up a test machine with everything I needed on Ubuntu running in a Microsoft Azure VM.

Loop Invariants Abbreviate Induction Proofs

Thu, 11 Sep 2014 07:07:00 -0400

It is often possible to avoid difficulties by proving the desired properties of our program by induction.

Mathematical Induction Makes Extrapolation Accurate

Thu, 04 Sep 2014 10:24:00 -0400

Mathematical induction is a technique for using the properties of natural numbers to prove claims about every natural number.

Sanity Checking By Extrapolation

Wed, 27 Aug 2014 13:22:00 -0400

It may be tempting to dismiss last week's problem as trivial, and argue that one should simply be able to construct a bunch of test cases and be done with it. However, it may not be easy to determine the correct results.

Why Testing Isn't Enough

Mon, 18 Aug 2014 08:52:00 -0400

Last week, I stated that software is hard to develop. This week, I would like to concentrate on two of the reasons why.

Why Is Software So Hard To Develop?

Thu, 07 Aug 2014 16:12:00 -0400

Software is hard to develop for many reasons: We must figure out what to do, do it, and ensure that we have done it correctly.

A Second Try at Refactoring Dijkstra's Example

Fri, 01 Aug 2014 10:31:00 -0400

If you compare my code with Dijkstra's original solution, you will see that in an odd way they are nearly logical duals of each other.

Simple Digital

Tue, 29 Jul 2014 10:45:00 -0400

It seemed a waste to put an I/O board in the system just for one switch closure reading.

Dijkstra's Example Simplified By Off-The-End Values: First Try

Wed, 23 Jul 2014 07:26:00 -0400

By keeping Dijkstra's strategy the same, but describing the ranges more consistently, the resulting program is easier to understand.

A Classic Example That Off-The-End Iterators Can Simplify

Fri, 18 Jul 2014 07:55:00 -0400

Let's examine a programming problem that Edsger Dijkstra calls "the problem of the Dutch national flag."

How To Use Reverse Iterators Without Getting Confused

Thu, 10 Jul 2014 10:09:00 -0400

This week we'll look at a concrete example of how to use reverse iterators.