Fwd: From pretext-support dynamic fill-in exercise allowed operations

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Charilaos Skiadas

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Jan 22, 2026, 12:33:58 PMJan 22

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As long as we are dreaming, here's what I would probably like to see. I hope I'm not stepping on too many toes. And there’s probably a ton of things I’m missing.

I think the bottom line is I like Rob’s suggestion for using some existing computation engine and would like to see the idea hashed out more. Though I would rather not limit the computation engine/language.

1. First a suggestion for a #context block that can go almost anywhere and is used to define a dictionary-map of name-value pairs, with values randomly generated or specific. It has an associated label used to reference it from elsewhere. Then #var entries can be used to get its values. An alternative to this would be a "setup" block to be delegated to the API described below, but to be ran on problem generation (i.e. when user views page, not when answering). I think this can have usefulness aside from this particular use-case.

2. The #evaluation tag gets a @language attribute and an @api attribute. Language can be anything and is simply passed to the API (with one exception below). The API is either a direct https link or a name for a link defined in the configs. A @context may also be specified.

3. PreTeXt does not specify or provide any APIs, but perhaps provides an in-browser javascript (possibly also python?) implementation. I.e. if language is js and no api is provided, we handle it in-browser.

4. An optional <code> block inside evaluation, for code to be run on user submission.

5. Each #evaluate -> #test can contain #apiobj whose body (or @value) is a boolean-evaluating expression in the language.

6. The API is given a json document containing the language, the context, the code block, and an array of the #apiobj test expressions. It is expected to "evaluate the code block and each test expression in the provided context and return the results of the test expressions".

7. I think that the PreTeXt team should be minimal in just specifying the form of the API request/response format, and not try to actually implement any APIs, beyond any in-browser things.

Here's the overall format I am envisioning:

<!-- Optional new thing, based on RNG work? Allows the creation of a context of RNG- or specific values --!>

<!-- To be accessed using <var ...> elsewhere --!>

<!-- Seed provided for static version or generated. --!>

<rng name="b" /> b set to random in [0,1] (type="double" implicit)

</context>

... use <fillin name="a" /> <-- entry by user, always named

... use <var context="..." name="b" /> <-- dynamically generated value provided by "context" above. Maybe use new <value> tag instead?

</statement>

<code>

... Code ran by the API on user submission.

... Receives as "local variables" the vars from context.

</code>

<test>

<apicmp> ... expression in the language ... </apicmp>

</test>

</evaluate>

</evaluation>

</exercise>

API request:

{

language: ...,

context: { seed: ..., b: ..., c: ... },

code: "...from <code> block...",

tests: ["testcode1", "testcode2", ...]

}

The API is responsible for placing the context appropriately in the code so they are local variables, and to add the testcode blocks and store their results.

API response:

{

success: true/false, // True if all tests passed

tests: [ true, false, false, ...] // Answer for each test.

}

Example (with context):

</context>

Compute the modulo: <var context="modulo" name="a" /> modulo <var context="modulo" name="a" /> equals <fillin name="c" />.

</statement>

<!-- No code needed--!>

</evaluation>

</exercise>

Charilaos Skiadas
Department of Mathematics
Hanover College

Begin forwarded message:

From: "'Rob Beezer' via PreTeXt support" <pretext...@googlegroups.com>
Subject: Re: [pretext-support] dynamic fill-in exercise allowed operations
Date: January 22, 2026 at 12:08:31 AM EST
To: pretext...@googlegroups.com
Reply-To: pretext...@googlegroups.com

Nothing here should be construed as minimizing Hunter's request.

The possible requests for supported operators is vast. How about polynomial multiplication with coefficients over a finite field? ;-) Yes, I know, out of scope right now.

Years ago, the WeBWorK folks added for me a function to pass computations to Sage and get back the results. It was a bit cumbersome to use (nobody's fault). Suppose there was a dedicated Sage Cell server that FITB problems could utilize? Imagine randomized questions about non-commutative rings for an abstract algebra course.

Not sure what markup, or much else, would look like. Just dreamin'.

Rob

On January 21, 2026 4:06:41 PM HST, "D. Brian Walton" <dbrian...@gmail.com> wrote:
Hunter,

The mod operator has not been implemented. It could be possible but would
require a dependent package is updated and could take some time. Note that
the library was designed for floating point arithmetic, and I haven't
thought about what happens with the modulus. Also, there is no integer
division implemented.

I do need to get back to that and will see about implementing that operator.

Brian

On Wed, Jan 21, 2026 at 3:38 PM Hunter Lehmann <hlehm...@gmail.com>
wrote:

Hi,

I am trying to create a dynamic exercise to compute the Hamming weight of
a random vector in F_p^n, say with entries x_1,...,x_6 in {0,1,..p-1}. Is
it possible to use a mod operator somehow in the computation of dynamic
values in PreTeXT?

The computation I would like to do is (x_1^4+x_2^4+...+x_6^4) mod 5. I
tried using % to invoke the mod operator but that just breaks the code.

Current exercise code below also.

Best,
Hunter

<exercise xml:id="daily-prep-fp-hamming-weight">
     <setup seed="123456">
       <de-object name="x1" context="number">
         <de-random distribution="discrete" min="0" max="4" by="1" />
       </de-object>
       <de-object name="x2" context="number">
         <de-random distribution="discrete" min="0" max="4" by="1" />
       </de-object>
       <de-object name="x3" context="number">
         <de-random distribution="discrete" min="0" max="4" by="1" />
       </de-object>
       <de-object name="x4" context="number">
         <de-random distribution="discrete" min="0" max="4" by="1" />
       </de-object>
       <de-object name="x5" context="number">
         <de-random distribution="discrete" min="0" max="4" by="1" />
       </de-object>
       <de-object name="x6" context="number">
         <de-random distribution="discrete" min="0" max="4" by="1" />
       </de-object>
       <de-object name="wt" context="number">
         <de-number>(x1^4+x2^4+x3^4+x4^4+x5^4+x6^4)%5</de-number>
       </de-object>
     </setup>
     <statement>
       <p>
         Compute the Hamming weight of <m>(<eval obj="x1"/>,<eval
obj="x2"/>,<eval obj="x3"/>,<eval obj="x4"/>,<eval obj="x5"/>,<eval
obj="x6"/>)</m>.
       </p>
       <p>
         <fillin mode="math" name="hamming_wt" ansobj="wt"
width="4"></fillin>
       </p>
     </statement>
     <evaluation>
       <evaluate name="hamming_wt">
         <test correct="yes">
         <mathcmp obj="wt" />
         </test>
       </evaluate>
     </evaluation>
   </exercise>

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