ChoiceScript's modulo operator is changing from "%" to "modulo"

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ChoiceScript’s modulo operator is changing from a simple percent sign % to the word modulo.

If you’ve written code like this:

*set remainder X % 12

You should upgrade to the latest ChoiceScript on github and use this instead:

*set remainder X modulo 12

What's a modulo?

In 2011, I added an advanced operator to ChoiceScript, the “modulo” operator. Here’s how I described it in the Advanced ChoiceScript guide.

You can also use the modulo operator “%” to calculate the remainder after taking a division. Modulo is pretty weird, but it’s has two particularly interesting uses. First, you can check whether a number X is evenly divisible by a number Y by checking whether X % Y = 0. Second, you can use it to get the fractional part of a number X, the stuff that comes after the decimal point, by calculating X % 1. For example, 3.14 % 1 = 0.14.

modulo is the new modulo

Now, instead of a percent sign % you should use the word modulo as the operator.

Here’s the updated documentation:

You can also use the modulo operator calculate the remainder after taking a division. Modulo is pretty weird, but it’s has two particularly interesting uses. First, you can check whether a number X is evenly divisible by a number Y by checking whether X modulo Y = 0. Second, you can use it to get the fractional part of a number X, the stuff that comes after the decimal point, by calculating X modulo 1. For example, 3.14 modulo 1 = 0.14.

Why change it?

I realized recently that I made a terrible mistake using a percent sign % as the modulo operator; it’s too close to the much more commonly used FairMath operators %+ and %-.

That means that when you want to do this:

*set strength %+ 20

it’s too easy to forget to type a + or a - and do this:

*set strength % 20

ChoiceScript won’t flag that as an error, because it is valid (but baffling) code. It means the same thing as:

*set strength strength % 20

That means: take the current strength, divide it by 20 and compute the remainder. So if your Strength was 50, *set strength % 20 would set your Strength to be 10. That’s almost certainly not what you wanted.

As of the latest version of ChoiceScript, both % and modulo work, but I’ve updated the Quicktest tool to print a warning if it catches you using % as a modulo operator. The warning will link back to this forum thread, inviting you to fix it by replacing your % with the word modulo.

At some point in the future (months from now, at least; maybe a year?) I’ll probably make a breaking change to ChoiceScript to remove the old % operator entirely. In that case, any use of % will be flagged as an error.

FairMath Isn't Changing

We’re not changing FairMath at all. *set strength %+ 20 still works the same way it used to.

If you don’t already know what “modulo” does, you’ll probably never need it, so don’t worry about it.

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So does this affect only fairmath then? What else is affected by the change?

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If this affects fairmath, I’m going to be pissed… / breathes deep, calms self /This may not affect fairmath at all… I shouldn’t jump to conclusions. I should first ask, will it?

Please, pleeeease, if this change is affecting fairmath, just -add- the use of ‘modulo’ and don’t de-activate %. The difference between typing % and typing modulo may not seem like much, but when you multiply it a few thousand times, it’s a lot of work. -_-’ If it’s not, then- it’s my mistake mistaking what was meant.

Or maybe I should clarify-
If I use *set strength %+4 … is that still valid code as fairmath, or will that be flagged as an error? Or would it only be flagged if I accidentally put *set strength % 4 ? (I can’t actually imagine doing this, but that’s just me)

Dagnabbit Neo, if I got worked up because I saw your post that it affects fairmath and it doesn’t, grr. Just grr. …but I would like to know if fairmath is affected by this change or not.

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It doesn’t affect fair math it’s just modulo that’s changing so a % on its on becomes modulo well that’s how I read that

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If that’s the case… I’ve got no problem with the change. I just … don’t want to have to change all of my fairmath around. :\ Which… kinda sounds selfish… but… thousands of instances. :scream:

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Your code is safe. I read it like @Nocturnal_Stillness as well.

and

You know the engine will be updated sooner or later … us slower writers are going to have to make changes anyways… although with your recent inspiration, your story is really coming along nicely.

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This change has no effect on FairMath. *set strength %+ 20 works fine and will continue to work.

(I’ve added a line to the original post to clarify this.)

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wilts with relief Oh thank goodness. relief smile

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I would imagine the amount of users this will affect is very minimal. Modulo can be used for working out remainders and wether a number is odd or even. At any rate, a fair change, it’s very good to see proper deprecation over a longer period of time.

I don’t suppose I could tempt you to allow “mod” for brevity…?

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I like the fact that you can Google modulo and get a Wikipedia page explaining the modulo operation.

Based on the games we’ve published, modulo is used rarely enough that the ulo won’t cause anybody RSI. :wink:

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Yeah, I’m probably one of the more programmery ChoiceScript authors, and… (checking) I’ve never used modulo. I’ve never seen the need.

I suppose if I did complex string manipulation (like Aaron Reed did?) I would, but I haven’t used too many special-case functions.