feat: implement DLMF attribute

[luigi-massacci]

Implement DLMF attribute. This allows users to link Mathlib declarations to DLMF entries.

The implementation here copies the LMFDB implementation (so in particular only checks that the character set in the ID is valid).

The DLMF (NIST Digital Library of Mathematical Functions) is a mathematical database for special functions and their applications by the National Institute of Standards and Technology (see wikipedia, and the DLMF itself).

It is also already linked to by the zbmath API for example.

---

[github-actions]

PR summary 44b96e2cc4

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ Lean.TSyntax.getDlmfId
+ dlmfIdAntiquot.parenthesizer
+ dlmfIdFn
+ dlmfIdKind
+ dlmfIdNoAntiquot
+ dlmfIdNoAntiquot.formatter
+ dlmfIdParser
+ test

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit 44b96e2).

• +14 new declarations
• −0 removed declarations

+Lean.PrettyPrinter.Formatter.dlmfIdNoAntiquot.formatter
+Lean.PrettyPrinter.Parenthesizer.dlmfIdAntiquot.parenthesizer
+Lean.TSyntax.getDlmfId
+Mathlib.CrossRef.Database.dlmf
+Mathlib.CrossRef.Database.dlmf.elim
+Mathlib.CrossRef.Database.dlmf.sizeOf_spec
+Mathlib.CrossRef.dlmfIdFn
+Mathlib.CrossRef.dlmfIdKind
+Mathlib.CrossRef.dlmfIdNoAntiquot
+Mathlib.CrossRef.dlmfIdParser
+Mathlib.CrossRef.dlmfIdParser.formatter
+Mathlib.CrossRef.dlmfIdParser.parenthesizer
+Mathlib.CrossRef.dlmfTag
+Mathlib.CrossRef.dlmfTags

---

No changes to strong technical debt.

No changes to weak technical debt.

Current commit 44b96e2cc4
Reference commit f682431588

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[grunweg]

Hi, thanks for your PR. What's DLMF, can you add a brief explanation?

[luigi-massacci]

Hello, I extended the PR description. I guess you have never been to FoCM ; )

[grunweg]

Thanks! Indeed, I haven't :-)