一般的なAPI — prefix/suffix/contains、split/join

let path = "/usr/local/bin"
print(path.hasPrefix("/usr"))   // true
print(path.hasSuffix("bin"))    // true
print(path.contains("local"))   // true

let note = "Welcome to Swift"
let found = note.lowercased().contains("swift".lowercased())
print(found)  // true

let csv = "Ada,Bob,Charlie"
let parts = csv.split(separator: ",")      // [Substring]
print(parts)                               // ["Ada","Bob","Charlie"]
print(parts.first ?? "")

let path = "///usr//local/bin"
let pieces1 = path.split(separator: "/", omittingEmptySubsequences: true)
let pieces2 = path.split(separator: "/", omittingEmptySubsequences: false)
print(pieces1)  // skips empties
print(pieces2)  // keeps empties

let vowels = "aeiou"
let tokens = "hello world".split(whereSeparator: { vowels.contains($0) })
print(tokens)

let words: [String] = ["one","two","three"]
let hyphen = words.joined(separator: "-")
print(hyphen)  // one-two-three