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77 lines
3.7 KiB
Markdown
77 lines
3.7 KiB
Markdown
---
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id: cpp-switch
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title: "C++ Switch"
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category: "Programming_Language"
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status: "draft"
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verification_status: "conceptual"
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canonical_id: ""
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aliases: ["switch case", "break keyword", "default keyword", "C++ switch 문"]
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duplicate_of: ""
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source_trust_level: "B"
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confidence_score: 0.85
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created_at: 2026-07-04
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updated_at: 2026-07-04
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review_reason: ""
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merge_history: []
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tags: ["cpp", "programming-language", "w3schools", "switch"]
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raw_sources: ["https://www.w3schools.com/cpp/cpp_switch.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[CPP Switch]]
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## 🎯 한 줄 통찰 (One-line insight)
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The syntax overview explicitly labels `break` and `default` as "optional" — a framing C's chapter never used — yet the same fall-through risk applies identically: without `break`, execution continues into subsequent cases regardless of match, meaning "optional" describes their SYNTACTIC status (the switch compiles without them) rather than their PRACTICAL necessity for correct behavior. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **`switch (expression)`** — evaluates the expression ONCE, then compares it against each `case` value. [S1]
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- **`case x:`** — a candidate value to match; its block runs if the switch expression equals `x`. [S1]
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- **`break`** — exits the switch block once a match is handled; described as OPTIONAL syntactically, though omitting it causes execution to fall through into later cases. [S1]
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- **`default:`** — runs if no case matches; also optional. [S1]
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## 📖 세부 내용 (Details)
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- Weekday-name lookup via switch: `int day = 4; switch (day) { case 1: cout << "Monday"; break; ... case 4: cout << "Thursday"; break; ... }` — outputs "Thursday" for day 4. [S1]
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- Using default for unmatched cases: `int day = 4; switch (day) { case 6: cout << "Today is Saturday"; break; case 7: cout << "Today is Sunday"; break; default: cout << "Looking forward to the Weekend"; }` — day 4 matches neither case 6 nor 7, so default runs. [S1]
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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- **break와 default는 "선택 사항"이지만 실질적으로는 거의 필수**: 문법적으로는 생략 가능하다고 명시되지만, break가 없으면 이후 case로 계속 실행이 이어지는(fall-through) 문제가 C 챕터와 동일하게 존재함이 확인됨. [S1]
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## 🛠️ 적용 사례 (Applied in summary)
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요일 번호(1-7)를 요일 이름으로 변환하는 예제와, 주말이 아닌 요일에 대해 default로 메시지를 출력하는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]
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## 💻 코드 패턴 (Code patterns)
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Using default to handle any value not matched by an explicit case (C++):
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```cpp
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int day = 4;
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switch (day) {
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case 6:
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cout << "Today is Saturday";
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break;
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case 7:
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cout << "Today is Sunday";
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break;
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default:
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cout << "Looking forward to the Weekend";
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}
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// Outputs "Looking forward to the Weekend"
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```
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## ✅ 검증 상태 및 신뢰도
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- **상태:** draft
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- **검증 단계:** conceptual
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- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
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- **신뢰 점수:** 0.85
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- **중복 검사 결과:** 신규 생성 (New discovery)
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## 🔗 지식 그래프 (Knowledge Graph)
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- **상위/루트:** [[C++ Tutorial]]
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- **관련 개념:** [[CPP Conditions RealLife]], [[CPP While Loop]], [[C Switch]]
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- **참조 맥락:** switch 섹션 유일 챕터 — 반복문(Loops) 섹션의 while 루프(While Loop) 챕터로 이어짐.
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## 📚 출처 (Sources)
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- [S1] W3Schools — C++ Switch — https://www.w3schools.com/cpp/cpp_switch.asp
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## 📝 변경 이력 (Change history)
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- 2026-07-04: Initial draft synthesized from the W3Schools "C++ Switch" page (Astra wiki-curation, P-Reinforce v3.1 format).
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