Consolidate the shared math basics in mcs; mds links to it #60

Move the general mathematics that CSCI 201 and the data science courses share out of Morrison-Lab/mds and into this repository.
mds will link to it, not include it.

Decided by Ezra on 2026-11-03.
Nothing has started: this issue records the plan and the reasoning behind it.
The working document is Math repos: where the shared content lives.

Decision

• mcs stays the CSCI 201 notes site, keeps its name, its URL and its 19 chapters, and becomes the home of the shared basics:
  • logic and proof writing
  • sets
  • functions and relations
  • induction and growth rates
  • number systems
  • expressions and algorithms
  • notation
• mds keeps the topics that only data science uses: algebra, calculus, linear algebra, vector calculus, optimization, measures and indicator functions.
  It links to mcs pages for shared definitions and does not add mcs as a submodule.
• No new repository.
  Splitting the course out into a separate repo (as maa) was considered and rejected.

Why

• The shared content sat in mds ("math for data science"), so the name did not match the contents.
• Linking keeps mds independent: mcs and mds never pin each other, and an mds render does not depend on mcs.
• Keeping the course in mcs moves about 300 files once, rather than also moving the course's 748 subfiles to a new repo.

Alternatives considered

Facts behind the plan (measured 2026-11-03)

• mds holds about 300 shared subfiles.
  By directory: proof-writing 103, sets 57, functions 55, expressions-algorithms 28, number-systems 26, relations 8, induction 6, growth-rates 6, notation 3.

• mcs has about 90 include lines that pull these subfiles in through its mds/ submodule.

• Other sites link to the shared mds pages.
  GitHub code search counted files linking to each page; the counts are a floor, since search returns at most one page of results.

  Page	Linking files
  sets.html	26 (lds 11, lds-site 9, sds 4, pds 2)
  functions.html	30 (lds 8, psw 7, sds 6, dds 5, pds 4)
  expressions-algorithms.html	30 or more (lds)
  number-systems.html	11 (lds 6, lds-site 5)
  notation.html	6
  proof-writing.html	3 (mcs 2, rme 1)

• GitHub Pages has no server-side redirects.
  A stub page with a meta refresh and a short script that keeps the #id does forward readers, so old links keep working while they are repointed.

• No students have the mcs URL yet (Ezra, 2026-11-03).

Plan

Each phase is its own PRs, and each leaves every site building and every old link working.

1. Freeze.
   • Close Record why mds is the shared home for the math mcs uses mds#606, which records the superseded "mds is the shared home" decision.
   • Hold Add the distributive laws and negating a conditional to Proof Writing mds#599 and land its content here instead.
   • Ask the owners of open shared-page PRs in mds (Cite Wikipedia after the proposition definition it supports mds#617 at the time of writing) to finish first.
2. Move the shared subfiles from mds into mcs.
   • Copy them by script into _subfiles/<topic>/, keeping every #id.
   • Repoint this repo's {{< include ../mds/_subfiles/... >}} lines to the local copies.
   • Verify each move with a content diff.
3. Give mcs a page for each shared topic, separate from the course chapters, so that other sites have a stable page to link to.
   One open question: whether these pages sit in their own navbar section or the course chapters serve as the link targets.
4. Turn each moved mds page into a redirect stub to the matching mcs page, keeping #ids.
   Delete the moved subfiles from mds.
5. Repoint mds's own cross-references.
   Where an mds page cites a moved definition, link to the published mcs page.
   That needs a filter like this repo's cross-page-refs.lua, in reverse.
6. Repoint incoming links.
   Run a scripted sweep of lds, lds-site, pds, sds, dds, psw and rme, one PR per repo.
   Then rerun the code search to confirm no hits remain on the old mds paths.
7. Update the records:
   • the CLAUDE.md of mcs and of mds (replacing mds's "Relationship to mcs" section);
   • ai-config's course-sequence fragment, which should put mcs before mds;
   • project memory.

Open questions

• May a scripted, pure-move PR exceed the push hook's 10-file cap, if a content diff verifies it?
  At 10 files per PR, phase 2 alone takes about 30 PRs.
• Does mcs keep the mds submodule for the DS-side content it still uses, such as the one algebra subfile and the references.bib?
  Or does it link to mds for those too?
• Should mcs's site title change to name the shared role, such as "Math for computational sciences"?

Generated by Claude Code