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by Leon Rosenshein

That's the way it is

I’ve said before that It Depends is just E_INSUFFICIENT_CONTEXT written so humans can understand it. There’s another common phrase that often hides a much deeper meaning.

That’s Just How It Is

The thing about that sentence is how passive and accepting it is. Particularly in the word just1. Without just it’s a description of the current state. Adding just adds another whole dimension. It changes the sentence for a description of what is to a comment on what is.

And implicit in that comment is context. The context that says not only are things the way they are, but that you’re powerless to do anything about it. I assert that that last part is untrue.

There may be limits on how much you can do, but it’s not nothing. At the very least, if you know that things are that way, you can expect it. And plan for it. Since I’m a software developer I’ll use a car analogy. Say you’re on a road trip and a road you want to use is closed.

You can drive right up to the sign, then stop and wait for someone to open the road, tell you to turn around and go home, or provide a detour. Or, depending on when you find out, you can plan a different route, decide not to go or to go somewhere else instead, or maybe decide a phone call gets you enough of what you want, and do that instead.

The difference is agency. If that’s just the way it is, you have no agency. On the other hand, if that’s the way it is, you have some control over your destiny. You can do something.

Coming back to software development, the same thing applies. There are events that happen that are outside your control. You do have to accept them. Requirements change. Hardware fails. You get bad input. What you do about it is up to you.

Depending on how much control you have, what you do is different. Sometimes you have enough control to prevent the problem. Or at least prevent the problem from impacting you. Ensure there are redundant systems to mitigate hardware issues. Sanitize your inputs when you get them, and if possible, where they are generated. Knowing that requirements change, leave some slack in the schedule. You’ll still run out of time (Hofstadter’s Law), but it won’t be as bad as it might have been.

Or maybe all you can do is add a bit of resilience to the system. Knowing that your inputs are unreliable, even after doing some sanitizing, reject them. Instead of crashing or passing on the problem to someone else, stop what you’re doing and return some kind of error to someone who can do something about it. If you can’t do that, at least log enough information so that you know what happened. And automate the recovery process. Or if you can’t do that, script it. There have been many times where I wasn’t in a position to prevent a problem from happening, but once I knew it could happen, I can’t think of a single time where there was nothing I could do to make things easier to diagnose and/or recover from the situation.

What makes it possible is the mindset change that comes from dropping the just. From changing a comment that makes you powerless to a statement of reality that you can do something about.

That’s just the way it is

That’s the way it is

Come to think of it, that’s good advice not just for software development, but for life in general.

  1. Just and But as modifiers, the difference between them, and how different people use them is a whole separate topic for another day. ↩︎

by Leon Rosenshein

The Power Of No

A long time ago I read a story by Eric Frank Russell, And Then There Were None. On the surface it’s a typical re-contact story. There was a great diaspora during which hundreds or thousands of interstellar ships left Earth to start new colonies. Shortly afterward, something happened, and contact was lost with all of them. Now, four hundred years later, the people or Earth are trying to reconnect with those colonies.

Without going in to too much detail, the ship (it’s never named) lands on planet K22g and the ambassador on board tries to find the folks in charge. Unfortunately, he can’t seem to do that. It turns out that the people who colonized the planet are followers of Gandhi approach to society and have turned civil disobedience and barter into their social system. In the story, two phrases that keep coming up and seem to define their society are F:IW and myob. It takes a while for the new arrivals to figure out that they are shorthand for “Freedom: I Won’t” and “mind your own business”. Those two phrases have a pretty strong impact on the more authoritarian, hierarchical, society represented by the ship’s crew.

There are lots of reasons why that social and economic system might not work at scale, and the story uses a bit of hyperbole to make it’s point, but who knows. It could work at small scale, like within a small community. It’s a pretty short story and it’s interesting to think about how such a society might actually work in the larger context.

You might be wondering how this relates to software development. After all, you can’t just tell your boss to “myob” or just say “I won’t” when you get a request. Or at least you can’t do that and expect there to not be any consequences.

It does, however, point out the power of politely saying “No” or “I’m responsible for that, and I think …”, and that’s where the connection is.

Just because someone asks you to do something, it doesn’t mean you should just drop everything and do it. Or try to do it in addition to whatever else you’re trying to do. That doesn’t work. It’s not scalable, it hurts quality. It slows things down and it keeps things from getting done. That doesn’t mean you should just say no and ignore the request. It just means you need to think about it and make sure you understand the impact of fulfilling the request.

Similarly, just saying “myob” when someone makes a request or suggestion isn’t the way to work with others. But you also shouldn’t just blindly take someone’s advice or let them set priorities or importance. You need to understand the “why” behind it. Once you understand the why, you can evaluate the statement and decide if it makes sense, would make things worse, or if there’s a better way to get the desired result. And again, you can’t do everything, so you should have the discussion if it’s the right thing to do.

Really, what they both come down to is realizing you’re responsible for what you do (and don’t do) and that you need to think about the value you’re providing. Not just immediately, but medium and long term as well. Saying “I Won’t”, when it’s appropriate, and with the proper understanding and justification, can give you the freedom to do the things that need to be done.

Saying “myob” or something like “Thanks for the advice. As the person/team responsible for doing X, here are a few things you may not have thought of.” is also very powerful. It can start the conversation around what’s important, what’s not, and why. When everyone understands that, the group makes better decisions together.

I’m not suggesting you respond to every request with “F:IW” or “myob”, but make sure you think about what the end result of giving a respectful version of those responses would be.

by Leon Rosenshein

What Are You Waiting For?

I’ve talked about the Eisenhower matrix before. Two orthogonal axes, importance, and urgency. It’s a good way to prioritize. The higher and further to the right, the higher the priority.

Another way to look at things is task priority, Leverage, Neutral, or Overhead. They all need to be done, but things with leverage are higher priority.

Or maybe you prefer the MoSCoW method. Must, Should, Could, and just as important, Won’t. That’s the priority order.

Three ways to prioritize. All you need to do is pick one, implement it, then reap the rewards, right? Well, that’s mostly right.

The thing that none of those schemes mention is that you have to not just to the work, you have to deliver the work. If you don’t deliver, then you haven’t added any value and you haven’t actually done the thing that you decided is most important.

Now here’s where it gets interesting. Delivering is work. So, it’s got a priority. Depending on your exact situation, that might be a lot of work, or it might be just a small amount of work. You can’t forget about it though.

Which leads to some interesting conflicts. You’ve done the work for the top 3 priorities on your list. They got done at about the same time. You could release (deliver) an update, but you could also wait for the next thing to be ready. There would be more value in your delivery, but it’s going to be later. Which do you choose?

It depends. If you decide to wait, some say you’re letting a lower priority (lower value) thing hold your high value thing hostage. Others say that you’re delivering more value, so the delay is worth it. Either might be true.

What lets you determine if you’re being held hostage or delivering more value over time is an understanding of the cost of delivery. The more delivery costs, the longer it takes, the more you end up packing things into each delivery. Instead of paying the cost of delivery for each item, you amortize it over multiple items. So, the delivery cost per item is lower. Standard unit economics, right?

Maybe, but maybe not. It depends on your perspective. Sure, the cost to you, as the producer is lower, but that doesn’t mean the value to the user is higher. It completely ignores the difference in value of having something right now compared to having something else later. The longer you wait to deliver something that could add value, the harder it is to make up the user’s lost value from not having it in hand now.

To make the calculation even worse, since you’ve done a good job figuring out the priority and value of the things to work on, by definition, the thing you’re waiting for has less value than what you’ve already done. If the difference in value is large enough, your user will never make up the difference.

So rather than cram more and more things into a delivery, which ends up delaying user value, and can make delivery take even longer, make delivery cheaper and faster. So you can put fewer things in each delivery. And deliver sooner.

And remember, this applies at all levels of development. Add the highest value thing now. Deliver it. Add the next highest value thing. Deliver that. Repeat. Or to put it GeePaw Hill’s terms, take many more much smaller steps.

by Leon Rosenshein

You ARE Allowed To Think Before You Type

I’m a big proponent of agile (lower case a) development practices and Test Driven Development (TDD) in particular. In my experience it conforms to the reality of changing understanding and moving requirements much better than BDUF. Like many things, there’s a spectrum ranging from BDUF to “Start typing and see what you come up with”. And in some specific scenarios, either one of those might be the right choice. But for the vast majority of us, in the vast majority of cases, the best choice is somewhere in the middle.

Unfortunately, the best sound bites are at the extremes. Things are so clear there. There’s no nuance or reality to get in your way. You end up with everything from “The product and architecture teams have specified every function/message/API call, so just go implement this skeleton.” to “Build me a website that tracks all of my activity. I’ll be back on Friday for a demo.” It’s easy to look at either of those and say that there’s no way that they’ll work. And they don’t.

So here’s another sound bite to get you thinking.

Continuous design is an interesting thing; it can be continuously coming up with a design (with some reversals) or it could be continuously testing pre-thought design ideas by implementing them and assessing.

Both are valid. You are allowed to think before typing.

     Tim Ottinger

I say nay, not just allowed. I would say you are required to think before you type.

It’s the messy middle, the land of “It Depends” where software engineering lives. The place where we need to understand not just what we’re doing, but why. To choose what to do for a valid reason, and just as importantly, choose what not to do. The way to do that is to think. Think about what your goals are. Think about what your constraints are. Think about the path, not just from 0 to 1, but from 1 to 10 as well.’

I’ve talked about only designing until you start speculating. But it goes even deeper than that. Until you’re done, you’re speculating. Even then, you might be wrong. You can (and should) design for the known knowns. You should have a approach for known unknows. But by definition, you don’t know the unknown unknowns, so you can’t design for them.

You might not be able to design for them, but you can keep from painting yourself into a corner. Especially if you’re using TDD to guide you, you have to think first. You can’t write the initial list of failing tests, let along the tests themselves, unless you have some idea of how things are going to work. How the events and data, the information is going to flow. How it’s going to be transformed.

To break things down into domains, you have to have some understanding of the situation. And not just the happiest path. You have to think about the edges. The failure cases. The places and ways things can go wrong. It’s only after you’ve thought about those things that you can create your domains and use tests to guide your development.

And all of that is speculation. You don’t know until you’ve tried.

So think. Then type. Then think some more. Then learn. Then design. And know that even those sound like separate things, they’re all happening somewhat concurrently. And that’s OK.

by Leon Rosenshein

10 Commandments of Code Review

Programming is a social activity. We work with other people, not in a vacuum. We share code with other people. We share ownership of code with other people. We share responsibility for code with other people. The sharing goes the other way as well. Others share their use cases, their requirements, and their experiences. One of the places where all of that comes together is in a code review.

In some cases, such as pair or mob programming, code review is a synchronous, ongoing activity, but that’s not what I’m going to talk about now. For most us, code review is an asynchronous event. Someone changes some code, throws it over a wall for review, then waits, more or less patiently, for a response. Eventually some sort of agreement is reached, and the code gets merged into the codebase. I have a lot of issues with the whole “throw it over the wall” approach, which is another thing to talk about at a later time. Meanwhile, here are 10 important things to keep in mind when writing or reviewing a code review.

Mel Brooks as Moses holding the 10 commandments.
  1. Thou shalt treat a code review request as an important task. Of course, you should give a thorough review when you give one, but there’s more to considering it important than that. It means declining quickly if you know you’re not going to be able to do the review. It means not putting it off for days. Different teams have different benchmarks, but 1 working day is a good rule of thumb.

  2. Thou shalt create code reviews knowing that others will read them. As I said earlier, always review your code review before sharing it. Make sure it has what it needs for the reviewer. The right files. The right explanation of why the change is being made. A description of the change that someone who didn’t make the change can understand. A list of tests to validate the change.

  3. Thou shalt not take comments personally. When reading comments on your review, remember, the comments are about the code, not you the author. Don’t get angry and ignore the comments. Take them seriously. Be willing to accept feedback and be willing to push back if you have a well thought out reasons. Nor shalt they make comments personal. Comment on the code, not the author.

  4. Thou shalt keep your review to a single topic. A code review should be about a single logical change. If you find you need to keep using and in your description, consider splitting the code review into multiple reviews.

  5. Thou shalt consider all feedback. Not just consider and ignore, but consider and respond. The response might be changing the code, it might be an explanation of why you’re not changing the code, or it might be agreement and a promise of a follow-on change.

  6. Thou shalt say why. Whether it’s the code review description, a code review comment, or a reply to a comment, always explain yourself. It can be as simple as “I agree” if there’s no disagreement, but “No” is not acceptable, “No because …” can be.

  7. Thou shalt not be absolutist. Writer or reviewer, be willing to compromise. Is good to have a strong opinion. It’s good to explain yourself. Like with everything else development, the right solution for a specific review depends on the context. Be willing to listen to the other people and work together to come up with a solution you all can more forward with. Again, remember that it’s OK to say there is more work to come, either right away or later when you know more about the situation.

  8. Thou shalt not argue with the style guide. One thing I like about Go is that most of the style guide is built into the language and there aren’t any options. The writer and the review might not agree with it, but it is what it is, and we all go with it. For other languages you might have more choices, but the review is not the place to argue them. If you need to argue about the style guide, do it outside the review.

  9. Thou shalt remember review feedback. The first time you receive some feedback it’s a learning experience. The second time you get the same feedback it’s helping you build a habit. If you get the same feedback a third or fourth time, stop for a minute and think about why. Understand where the feedback is coming from and incorporate the learning into your future reviews. If you’re not learning from your reviews, you’re being disrespectful to your reviewers.

  10. Though shalt treat your review partners as you want to be treated. Just like that other golden rule, whether you’re the writer or reviewer, think about how your partner will feel. Think about how you would feel if you were on the other side of the equation. Then act the way you would want yourself to act.

Code reviews, regardless of which side you’re on, are there to help produce the most value you can. But they can be so much more. They can be teaching and learning tools. They can be vehicles for sharing. They can be a gift that you give to yourself and that teams give to themselves.

If you let them. So take advantage of your opportunities when you can.

by Leon Rosenshein


There are lots of reasons to have high internal software quality (ISQ). Minimizing WTFs/min is only one of them. One of the biggest reasons is not what ISQ does for you today, but what it will do for you tomorrow. The optionality it gives you for the future.

So what is optionality, and why should we care?

optionality (countable and uncountable, plural optionalities)

  1. (finance, business) The value of additional optional investment opportunities available only after having made an initial investment.
        The short-term payoff for this is modest, but the optionality value is enormous.
  2. Quality or state in which choice or discretion is allowed.
        Some offices do not follow the corporate procedure, due to a culture of optionality.

We care about optionality because software is all about change. In this case we care about both senses of the word. Sure, a particular release is a snapshot of a moment in time, and unchanging, but even in the days of shrink-wrapped software that you got off a shelf, there were often updates and patches, to say nothing of next year’s version. Now, with Software as a Service, Web execution, downloadable content, it’s not unusual to have multiple releases on any given day. So software changes, and optionality is important.

Some of you might be saying “But I write embedded code for an unconnected device. My code can’t be updated. I don’t care about change.” It’s true that once released that code can’t change. But right up until release the requirements can change, and they often do. So even in that case, writing software is about change.

Even more fundamentally, every character you add, remove, or change (there’s that word again) is a change to the software. The progression of a product, from idea, to design, to code, to release, is about change. Again, development, of any kind, including software, is about change.

Given that you know you’ll need to make changes, even if you can’t know what some of those changes are, giving yourself the optionality to go in whatever direction you need to go in is important. And that’s the biggest benefit of ISQ. Knowing that you can tackle the unknown unknowns that you know are coming with confidence.

ISQ is things like low coupling. That’s what lets you adjust the internals of one part of your code without having to worry about how it will impact other parts. As long as you don’t break your interface contract, you can do what you need to safely. Your unit tests, which are a part of high ISQ, let you know that you’re maintaining your contract.

ISQ is things like readability. I’ve talked about Coding for the Maintainer many times. Doing that is part of having high ISQ. If it’s easy to tell what’s happening, why choices were made, and more importantly, why other choices weren’t made, you have more options available to you. You can change your mind with more understanding, which leads to better decisions.

ISQ is things designing for test and using well written tests. If you have designed your components to be tested, you have lower coupling (see above) and you can test things without worrying about the testability of a dependency. It’s making sure your tests are tied to the outcomes of the things being tested, not the process of the thing being tested. It’s using fakes, mocks, stubs, and the real thing for dependencies at the right time1. If you do those things, you can make changes with the confidence.

There are lots of other things that go into ISQ, but just doing those things isn’t the goal. And just having higher ISQ isn’t the goal. The goal is to give yourself more optionality. Higher ISQ is just one way to get that optionality. To have confidence that you’ve changed what you wanted to change, and just as importantly, that you haven’t changed anything you didn’t want to change.

  1. When to use fakes, mocks, stubs, and the real thing is a whole different topic for another time. ↩︎

by Leon Rosenshein

Review Your Own Code Review

I’ve talked about code reviews before. There’s are things you should do when you review code, and there are things you shouldn’t do. Most of those things are about what to do when reviewing someone else’s code. The rest are about what goes into preparing a good code review.

I stand by those ideas. But there’s on important thing that goes into preparing a good code review that I haven’t mentioned in the past. That’s reviewing your own code reviews, before asking anyone else to look at them.

One of the biggest reasons is to know for sure exactly what is going into the review. In order to write a good title and summary, you need to know what you’re summarizing. You want to be clear about what’s included, and for that you need to know.

It gives you a chance to see how many “ands” you put into your summary. Very often you find that to do the thing you set out to do you need to make a bunch of other changes to make it possible. Since each review should do one thing, the self-review is a good time to catch that you should split the review up into multiple reviews. NB: Your reviewers will thank you.

Since you’re looking at the entire thing at once, are you being consistent? Are you being readable? Do things visually flow? Not just formatting, you have rules and formatters for that (don’t you?), but in structure and naming. Do you call something inventory in one place and stock in another? Make them the same. Did your method grow to 300+ lines? Break it up. Are you calling methods from hither and yon? Do you need to jump around/across files to follow what’s happening? Consider bringing things physically closer together to make reading/debugging easier.

Did you leave yourself a note to looks at something related later? I do that all the time since I don’t want to change contexts and track something down. I also often forget that I wanted to track that thing down, so seeing the note during the review gives me another oportunity to follow through.

Another thing you get from self-review is the chance to notice any debug helpers you left in the code. Things like extra print or log statements, parameter overrides, or changed defaults. Once you find them you’ve got an opportunity to change things. Should those prints be log messages? Should the logs be at a different level? Are you changing or adding a default that needs to be documented?

Speaking of documentation, this is also a good time to check and make sure that there is appropriate documentation for what you did, why you did it, and why you didn’t do something else. You’ve already done it once, but this is your chance to look at the changes in totality and make sure.

What about unit tests and/or code coverage. Do you have enough? Neither are guarantees, and you hopefully have automated systems that will check this for you, but being a good neighbor means the code under review is done. If you have folks do a review its better if you’re sure all the existing tests still pass, and any needed tests have been added. If not, you’re going to have tyo go back to your reviewer and ask them to review things all over again once you fix those problems. That is not the way to make friends.

What it comes down to, and what all these benefits add up to, is the chance to make sure your change is done and really ready for review before you send it on to others. Between context switches and the time taken to do the review, you’re about to cause multiple man hours of work across multiple people. It’s on you to do your homework first.

by Leon Rosenshein

Demands ...

What if I told you that your time was limited? That the number of things you could get done in any given period was limited? You’d probably say “I know that.” And you do. You know you can’t do everything, and you know you can’t do everything at once. However, you’re not in control of what you need to do. Hopefully you’re involved in the decision, but while the how is often fully on the development team, the what and the why usually aren’t.

But what if I told you that you are in complete control of a big part of what you need to do? Broadly speaking, you can split what you need to do into two categories. The things you need to do to add value, and the things you need to do to because of things you did to yourself.

But what if I told you that you have control morpheus meme.

Adding customer value is pretty straightforward. A new feature. A new capability. Automating the manual. That’s the value demand. The demand on your time/capability where the result is customer value. And providing customer value is what we’re all here for.

The other category, things you need to do because of things you did to yourself, is the set of demands on your time that includes things like keeping the lights on, responding to customer issues, bug fixes, outage response, and other similar “customer service” demands.

That’s what Vanguard calls Failure Demand. They’re even more prescriptive about what Failure Demand is. To them:

It is demand caused by a failure to do something or do something right for the customer. Customers come back, making further demands, unnecessarily consuming the organization’s resources because the service they receive is ineffective.

Put that way, it’s simple. Everything is relative to the customer (internal or external). Add up the two things and that’s the total demand. The amount you do is constrained, so for a given amount of capacity, to maximize value demand met, you minimize failure demand met.

Equation showing that the sum of value demand and failure demand equals system capacity.

Sure, you could just not do the failure demand, and for a short time you can get away with it. But do it for too long and you lose customers because no matter how much value you think you’re adding, they aren’t getting enough value because of the failure demand they’re living with. A much more sustainable way of dealing with it is to minimize the amount of failure demand that your customers are generating. You do that by moving a little slower. By being more careful to finish what you’re doing. To not release those issues in the first place.

You can’t know everything up front, and you will learn things from releasing, but by paying attention to what you’re doing, by having sufficient testing, by making things resilient, by improving quality overall, you reduce failure demand.

Which naturally gives you more capacity to respond to value demand.

by Leon Rosenshein

The Tao Of Pooh

I’ve always liked Winnie the Pooh. He may say he’s a bear of very little brain, but I think he’s got a lot of deep understanding that we could all benefit from.

Winnie the Pooh talking to piglet, saying To know the way, we go the way, we do the way. The way we do, the things we do, it's all there in front of you.

While I’m reasonably sure Pooh was not an extreme programmer, that’s not a bad paraphrase of what extreme programming and the agile manifesto are getting at. Do the work and the work will show you what needs to be done. You do what you can do, and you find out how to do the next thing.

To know the way,
we go the way,
we do the way.

The way we do,
the things we do,
it’s all there in front of you.

But if you try too hard to see it,
you’ll only become confused.

I am me and you are you.
As you can see;
but when you do
the things that you can do,
you will find the way.

The way will follow you.

For example, I used to fight with my code sometimes. Or more accurately, I fought against it, trying to make it do what I wanted, not what it wanted. Then I realized I was wrong. And not just wrong to be fighting against my code, but wrong about code ownership and wrong about what I was fighting against.

Firstly, and long term, probably the more important, was that it wasn’t really my code. I might have written it, and I might have been the person that knew the most about it, but it wasn’t “mine”. Code has its own existence and its own purpose. The work I’m doing with the code is designed to get something done. To add value to the code, to the system. Not to make me more valuable by owning more code. It’s not about me, and while Imposter Syndrome is real, beating your head against some code is not the way to approach it.

Second, and the more tactical part, is that you can’t fight against code. You can’t make it do anything it doesn’t know how to do. You can use it different ways, and for different things. You can use it in ways that it was expected to be used, you can find new ways to use it in new situations, and you can use it in ways that are different and the opposite of how the original writers intended it to be used, but you (largely) can’t make it do something it doesn’t know how to do.

Instead, what you’re really fighting against is yourself. Your understanding (or lack of understanding) of what the code is doing and is supposed to do. How it works, and what its side effects are. The way to approach that is not through fighting or struggling, but through education. Reading documentation. Reading code. Exercising code to characterize how it actually responds (because documentation isn’t always correct). When you understand yourself and your biases, when you understand the code, its strengths, weaknesses, abilities, and constraints, you find that you’re working together, with the code to meet your goals, instead of against it. You find you’ll go farther and you’ll get there faster.

So like Pooh says, it’s all there for you to see. You just need to not try so hard. Let yourself see how things are and how they should be. And that will lead you to the way.

by Leon Rosenshein

Primitive Obsession and Boolean Blindness

George Boole brought us Boolean algebra. There’s tremendous benefit in using it. Boolean algegra is one of the foundations of computer science and factors into a lot of what we do as developers. But sometimes, it can also blind you to a deeper truth.

I’ve talked about primitive obsession before. It’s where you use a base type to represent a specific domain type. Like storing a URI as a string, It works, and its faster at first, but it’s also very limiting. Instead of building an object that understands itself, you build the functionality to use the primitive type as if it were the domain type. It works, but future you is going to be unhappy.

Boolean blindness is a specific kind of primitive obsession. That’s where you use a Boolean value to store the value of something that is really more nuanced than that. There are two common ways this happens.

One is where things don’t map neatly to True/False. Instead, you have some possible list of values and some of them would be considered True and others would be considered False. This can happen a lot in state machines, like bug databases. You often want to know if a particular entry is open, active, or closed. That entry, however, can have many states than that. You could have a Boolean for every possible state and some complex logic that keeps them all updated, at the same time, but that’s brittle and error-prone. A better choice might be to have a enum for the possible states and a way to determine if a given state IsOpen or IsClosed.

The other case is where there is a very clear definition of True/False, but there’s more data you want to store. In my Wikipedia entry (if I had one), there would be a birth date, but no date of death. I could have two variables, a Boolean called isDead and a Date called diedOn. The second would only be meaningful if the first were true. That works, but again, that’s very brittle. You need to make sure that diedOn is only used when isDead is True, and that any change to diedOn changes isDead appropriately. A better choice here would be some kind of nullable or optional date, diedOn. If diedOn has a value then I’m dead and the value is when I died. If it doesn’t I’m still alive. It might be wrong, but it can’t be inconsistent.1 It’s easy to imagine a much more complex class where isTrue is a complicated function of a bunch of internal state. Most languages won’t let you define the truthiness of a class, but you can imitate it by having a method on the class IsTrue() that handles that for you.

In other words, sometimes Boolean Blindness hides information by turning a multi-state thing into a two-state thing. In other cases you have the information and you just end up repeating yourself (and often getting out of sync). And sometimes that Boolean really is what you want. The trick is to actually make the choice knowingly, not by default or by mistake.

  1. There’s a whole different article around consistency vs correctness, but that’s something for the future. ↩︎