`SSG/Util.lean`

Explanation legend Lean4 Domain Explanation Language (L4DEL)

L4DEL explanations are a separate layer. They do not change the Lean source. Intuition is explanatory prose; numbered items are a reading path; sources link the wording back to evidence.

L4DEL: Lean4 Domain Explanation Language

Annotation provenance. This overlay contains 8 curated AI-written annotations and 3305 mechanical source-derived annotations. They have not been human-reviewed as explanations; treat them as unverified and not mathematical authority. Retained generation history: The 71 original curated annotations were produced in a Claude Sonnet 5.5 session at medium effort; Claude Opus 5.5 is recorded in that session as the advisor model, not the direct author. The bulk source-derived expansion was generated mechanically from pinned source comments by tooling developed in a GPT-5.6 Sol session at ultra reasoning; GPT-5.6 Sol did not originate the quoted source prose. On 2026-10-17 the mechanically generated source-comment annotations of the Formal Conjectures, Carleson, FLT, PFR, CompFiles, Mathematics in Lean and Theorem Proving in Lean overlays were regenerated by the same generator after three corrections made in a Claude Sonnet 5.5 session: titles no longer cut a sentence inside mathematics or end on a dangling word, workflow markers are removed from the quoted prose, and declaration names follow the scanner's namespace resolution. The boilerplate step line was dropped, and comments that were only a row of dashes no longer yield annotations. No new prose was written and no human review is claimed.

Credit: The upstream authors and contributors retain credit for the project and mathematics. lean4-explainer only renders their pinned source and adds the separately disclosed explanation layer.

Project sources: Pinned compfiles documentation, Pinned compfiles corpus index

4 declarations, 0 contain sorry, 0 declared as axioms

Imported by 3 files

def htmlEscape Escape for HTML text content line 6 source
Source documentation
Escape for HTML text content

standard axioms: Classical.choice, Quot.sound, propext what this means
Statement uses: String
Proof uses: String.foldl, Char, HAppend.hAppend, htmlEscape.match_1, Unit, Char.toString
2 instances, coercions and auxiliary constants left out.
```
def htmlEscape (s : String) : String :=
…
```
def htmlEscapeAttr Escape for HTML attribute values (superset of text escaping) line 16 source
Source documentation
Escape for HTML attribute values (superset of text escaping)

standard axioms: Classical.choice, Quot.sound, propext what this means
Statement uses: String
Proof uses: htmlEscape
```
def htmlEscapeAttr (s : String) : String :=
…
```
def uriEncodeComponent Percent-encode a URI component (RFC 3986 unreserved chars preserved) line 20 source
Source documentation
Percent-encode a URI component (RFC 3986 unreserved chars preserved)

standard axioms: Classical.choice, Quot.sound, propext what this means
Statement uses: String
Proof uses: String.foldl, Char, ite, Eq, Bool, Bool.or, Char.isAlphanum, BEq.beq, Char.ofNat, Bool.true, String.push, ByteArray.foldl, UInt8, HAppend.hAppend, ToString.toString, uriEncodeComponent.hexDigit, HDiv.hDiv, OfNat.ofNat, HMod.hMod, String.toUTF8 and 5 more
13 instances, coercions and auxiliary constants left out.
```
def uriEncodeComponent (s : String) : String :=
…
```
def uriEncodePath Encode a full URI path (preserves / and other structure chars) line 31 source
Source documentation
Encode a full URI path (preserves / and other structure chars)

standard axioms: Classical.choice, Quot.sound, propext what this means
Statement uses: String
Proof uses: String.intercalate, List.map, uriEncodeComponent, String.splitOn
```
def uriEncodePath (s : String) : String :=
…
```