2nd/10_Wiki/Topic_Programming/Topic_C/C_Conditions_Nested.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
c-conditions-nested	C Nested If	Programming_Language	draft	conceptual		if inside if dependent conditions C 중첩 if		B	0.84	2026-07-04	2026-07-04			c programming-language w3schools conditions nested-if	https://www.w3schools.com/c/c_conditions_nested.php

C Nested If

🎯 한 줄 통찰 (One-line insight)

A nested if only ever gets EVALUATED at all if the outer condition is true — the voting-and-citizenship example never even checks isCitizen if age >= 18 is false, meaning nesting isn't just visual grouping of related checks, it's a genuine short-circuit optimization where the inner condition's cost (and its own true/false branches) is entirely skipped when the outer gate fails. [S1]

🧠 핵심 개념 (Core concepts)

• Nested if — placing an if statement inside another if's block, so the inner condition is only checked when the outer condition is already true. [S1]
• Dependent condition modeling — naturally expresses "check B only if A holds" logic, like age eligibility gating a citizenship check. [S1]
• Depth caution — the source explicitly warns against nesting too deeply, as it can hurt readability; nested if is commonly combined with else/else if for richer decision trees. [S1]

📖 세부 내용 (Details)

• Basic two-level nesting: int x = 15; int y = 25; if (x > 10) { printf("x is greater than 10\n"); if (y > 20) { printf("y is also greater than 20\n"); } } — both print since both conditions hold. [S1]
• Voting + citizenship real-life example: int age = 20; bool isCitizen = true; if (age >= 18) { printf("Old enough to vote.\n"); if (isCitizen) { printf("And you are a citizen, so you can vote!\n"); } else { printf("But you must be a citizen to vote.\n"); } } else { printf("Not old enough to vote.\n"); }. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 중첩 if의 단축 평가 효과: 바깥 조건이 거짓이면 안쪽 if의 조건 자체가 아예 평가되지 않는다는 점이 나이/시민권 예제로 확인됨 — 관련 없는 하위 조건을 불필요하게 검사하지 않는 효율성을 제공. [S1]

🛠️ 적용 사례 (Applied in summary)

투표 가능 연령(18세 이상)을 먼저 확인하고, 그 안에서만 시민권 여부를 추가로 확인하는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

💻 코드 패턴 (Code patterns)

An inner condition (citizenship) checked only when the outer condition (age) already holds (C):

int age = 20;
bool isCitizen = true;
if (age >= 18) {
  printf("Old enough to vote.\n");
  if (isCitizen) {
    printf("And you are a citizen, so you can vote!\n");
  } else {
    printf("But you must be a citizen to vote.\n");
  }
} else {
  printf("Not old enough to vote.\n");
}

✅ 검증 상태 및 신뢰도

• 상태: draft
• 검증 단계: conceptual
• 출처 신뢰도: B (W3Schools — widely used educational reference, not a primary standards body)
• 신뢰 점수: 0.84
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: C Tutorial
• 관련 개념: C Conditions Logical, C Conditions RealLife
• 참조 맥락: 중첩 if — 조건문 실전 예제(Conditions RealLife) 챕터로 이어짐.

📚 출처 (Sources)

• [S1] W3Schools — C Nested If — https://www.w3schools.com/c/c_conditions_nested.php

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "C Nested If" page (Astra wiki-curation, P-Reinforce v3.1 format).