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77 lines
3.7 KiB
Markdown
77 lines
3.7 KiB
Markdown
---
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id: cpp-functions
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title: "C++ Functions"
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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: ["void function", "function call", "declaration order matters", "C++ 함수"]
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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", "functions"]
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raw_sources: ["https://www.w3schools.com/cpp/cpp_functions.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[CPP Functions]]
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## 🎯 한 줄 통찰 (One-line insight)
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Calling a function BEFORE it's defined (with no prior declaration) is an explicit ERROR in C++ — the source shows `myFunction()` called inside `main()` at the top, with its full definition written BELOW, producing a compile error — a stricter behavior than what C-style top-down reading might suggest, meaning the declaration-above/definition-below organizational pattern isn't just a style preference here, it's the FIX for a real compile failure, not merely cosmetic. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Function** — a block of code that only runs when CALLED. [S1]
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- **`void` return type** — the function returns no value. [S1]
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- **Calling before defining fails without a declaration** — if `myFunction()` is called in `main()` but only DEFINED below `main()` with no prior declaration, it's a compile error. [S1]
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- **Declaration + definition split** — writing `void myFunction();` above `main()` and the full body below fixes the ordering problem while keeping code organized. [S1]
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## 📖 세부 내용 (Details)
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- The error case (calling before any declaration exists): `int main() { myFunction(); return 0; } void myFunction() { cout << "..."; } // Error`. [S1]
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- The fix using forward declaration: `void myFunction(); int main() { myFunction(); return 0; } void myFunction() { cout << "I just got executed!"; }`. [S1]
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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- **선언 없이 정의보다 먼저 호출하면 명시적 에러**: main() 안에서 함수를 호출하고 그 정의가 아래에 있을 뿐 사전 선언이 없으면 컴파일 에러가 발생한다는 점이 직접 예시로 확인됨 — C 챕터보다 이 문제를 더 명확히 강조함. [S1]
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## 🛠️ 적용 사례 (Applied in summary)
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현재 발견된 실제 적용 사례가 없습니다 — 함수 선언을 main() 위에 두고 정의를 아래에 두는 구조가 컴파일 에러를 피하면서 코드 가독성도 높이는 실전 표준 관행이다. [S1]
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## 💻 코드 패턴 (Code patterns)
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Forward-declaring a function above main() so it can be called before its full definition (C++):
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```cpp
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// Function declaration
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void myFunction();
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int main() {
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myFunction(); // works because of the forward declaration above
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return 0;
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}
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// Function definition
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void myFunction() {
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cout << "I just got executed!";
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}
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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 Memory Management New]], [[CPP Function Param]], [[C Functions]]
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- **참조 맥락:** 함수 섹션 첫 챕터 — 함수 매개변수(Function Param) 챕터로 이어짐.
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## 📚 출처 (Sources)
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- [S1] W3Schools — C++ Functions — https://www.w3schools.com/cpp/cpp_functions.asp
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## 📝 변경 이력 (Change history)
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- 2026-07-04: Initial draft synthesized from the W3Schools "C++ Functions" page (Astra wiki-curation, P-Reinforce v3.1 format).
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