Add solution to Exercise 3.12 (append vs append_mutator)#1195
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Adds a SOLUTION giving the two missing responses for tail(x): ["b", null] after append (x is not modified), and ["b", ["c", ["d", null]]] after append_mutator (x's last pair is spliced to y). The explanation notes that z shares its last two pairs ["c", ["d", null]] with y, addressing the maintainer's correction on the issue. Also fixes a typo in z's printed value (['d, null] -> ['d', null]). Closes #860 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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This pull request fixes a syntax typo in a JavaScript output snippet and adds a detailed solution block explaining the difference between list copying in append and list mutation in append_mutator. The reviewer suggested improving the consistency of the solution block by replacing <P/> tags with blank lines and correcting a minor inaccuracy regarding structure sharing.
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Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
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Adds a
<SOLUTION>to Exercise 3.12 (ex:append) inxml/chapter3/section3/subsection1.xml. The exercise asks for the two missingtail(x)responses and a box-and-pointer explanation, and had no solution.Responses
const z = append(x, y):tail(x)is["b", null]—appendcopies the pairs ofxand does not modify it.const w = append_mutator(x, y):tail(x)is["b", ["c", ["d", null]]]—append_mutatorsplicesyonto the last pair ofx, mutatingx.On the diagram correction
The explanation explicitly notes that the result
zshares its last two pairs["c", ["d", null]]withy(only the pairs holding"a"and"b"are freshly copied) — addressing your comment on the issue that the contributor's first diagram was wrong because it didn't show this sharing. I wrote the solution as prose (matching the JS-focused style of the adjacentex:mysterysolution) rather than embedding the contributed images, since no solution images exist in the repo and the first one was incorrect.Also
z:["a", ["b", ["c", ["d, null]]]]→["d", null](missing closing quote; thewvalue just below already had it right).Checks
<JAVASCRIPTINLINE>quote style matches the surrounding solutions (literal").Closes #860