QuantEcon / QuantEcon/lecture-python-advanced.myst
calvo.md and calvo_machine_learn.md: $L^2$ definition removed but notation still used
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Description
Summary
PR #312 ("[amss] Update Tom's edits to AMSS and Calvo Lectures") removed the local definition of square-summable / $L^2$ from the three Calvo lectures, but several places still use the $L^2$ notation without a definition, leaving readers without context for what space is being referenced.
Locations still using L^2 after the definition was removed
lectures/calvo.md — 7 occurrences
| Line | Context |
|---|---|
| 330 | $\vec \mu =\{\mu_t\}_{t=0}^\infty \in L^2$ into an inflation sequence |
| 331 | $\vec \theta = \{\theta_t\}_{t=0}^\infty \in L^2$. |
| 334 | $\vec v = \{v_t\}_{t=0}^\infty \in L^2$ that satisfies |
| 340 | sequence $\vec \mu \in L^2$. |
| 342 | At this point $\vec \mu \in L^2$ is an arbitrary exogenous policy. |
| 453 | $\{x_{t+1}, \mu_t \}_{t=0}^\infty$ sequences, with each sequence belonging to $L^2$: |
| 460 | where we require that $\{x_{t+1}, \mu_t \}_{t=0}^\infty \in L^2 \times L^2 .$ |
lectures/calvo_machine_learn.md — 1 occurrence
| Line | Context |
|---|---|
| 208 | \vec \theta \in L^2 |
lectures/calvo_abreu.md — clean
calvo_abreu.md had the same definition removed and no remaining $L^2$ references, so it's consistent.
Why it matters
Earlier in each affected lecture, the assumption on $\vec\mu$ was weakened from "square-summable" to "bounded" (a reasonable simplification — the discounted geometric structure of the forward solution is well-defined under boundedness). But the later sections that still use $L^2$ now reference an undefined space. A reader going top-to-bottom encounters $\vec\mu \in L^2$ at line 330+ in calvo.md with no prior definition or external pointer.
Suggested fix
Either:
- Reintroduce a brief $L^2$ definition in each of the two affected lectures (could be a one-liner: "$L^2$ denotes the space of square-summable sequences"), or
- Replace the remaining $L^2$ references with the weaker "bounded" framing if that's now the intended assumption end-to-end, or
- Cross-link to a single canonical definition in one of these lectures and have the others reference it.
Context
Surfaced by GitHub Copilot's PR review during sync of these lectures into lecture-dp (QuantEcon/lecture-dp#11). The PR is byte-identical to this repo's current main, so this issue belongs upstream.
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Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the affected sections in lectures/calvo.md and lectures/calvo_machine_learn.md, then review PR #312 to understand why the L^2 definition was removed. Decide whether the intended assumption is a restored definition, bounded sequences, or a cross-link, and apply that choice to all listed occurrences. Check the rendered lecture text to confirm no undefined L^2 references remain.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- latex, markdown
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 68/100