Stringly Typed Booleans

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I’m getting rather hacked off seeing boolean properties typed as strings. Stringly typed is a phrase I learnt off a post from the excellent Coding Horror blog and it describes a phenomena whereby properties that are of a specific type, e.g. Boolean, Date, int, are stored needlessly as strings.

I’m working on a website that communicates with a money laundering service to check whether an individual is “bad” or not. Individuals can pass the test, but importantly it is possible to pass the test with some warning flags raised. If any of the warning flags are raised then an email should be sent off to compliance for them to do…whatever it is they do. Fair enough right?

The warning flags are obviously booleans. There was either a warning raised or there wasn’t – there are no two ways about it (no pun intended). In the serialized response, the warning flags are encoded as “Yes” or “No”…which is understandable. Now, upon receiving the response, it is parsed and turned into an internal representation. This is where things get really weird. The programmer that coded the object that stores the response from the service has decided to encode the warnings as strings, initialised to “”. Which is totally fucking bonkers.

Why?

Well, now our boolean warnings aren’t really booleans – they have WAY more than two possible values and the meaning of these values is subjective. One may consider “”, null, “No” as false, but could conceivably also consider “false” or “0″. We get the same sort of problem with true – “Yes”, “1″, “true” and then we get a whole load of unknown values which is every other possible string in the world. Which might be considered to be true.

So how the hell can any number of programmers work on this piece of code without introducing errors because of differing definitions of truthy and falsey values? Well, they can’t. To illustrate the problem further, even loosely typed languages differ in their boolean coercion, for example JavaScript and PHP:

<script>
if("0") alert('Opposite day!');
</script>

<?php
if("0") echo 'Opposite day!';
?>

JavaScript considers “0″ true but PHP considers it false. Personally I think JavaScript is “right” here, but as I said before, it is totally subjective.

The icing on the cake is of course the extra code you have to write to check the truthy or falsey string values. Something along the lines of “if x is not null and not empty and not the word No then it is probably true…probably”, which would otherwise have been coded as “if x then true” if x was a boolean – which is orders of magnitude shorter.

Of course, there are some bat shit crazy strongly typed languages that allow you to assign null to a Boolean, but that is a different story altogether.

5,021 thoughts on “Stringly Typed Booleans”

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