Exercise 2: Sorting Xcode Skills — Possible Solution
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TASK
Sort into "language and platform," "general programming concept," or
"Xcode-specific tooling": Swift, breakpoints as an idea, Instruments, SwiftUI
Previews, the iOS SDK.

ANSWER

  Swift                        -> language and platform
  The iOS SDK                  -> language and platform
  Breakpoints as an idea       -> general programming concept
  Instruments                  -> Xcode-specific tooling
  SwiftUI Previews             -> Xcode-specific tooling

REASONING
- Swift and the iOS SDK exist independently of which editor you use.
- A breakpoint is a general debugging idea. The specific windows, menus and
  the LLDB commands Xcode wraps are how Xcode presents it; Chapter 4 covers
  those.
- Instruments and SwiftUI Previews are listed among what Xcode bundles.

CAUTION
"Xcode-specific" here means bundled with Xcode according to this chapter's
sources. I did not verify whether Instruments or Previews can be used
without Xcode, so the label is a reading of the chapter, not a tested fact.

WHY THIS WORKS AS AN ANSWER
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Each item is placed with a reason, and the one uncertain classification is
flagged instead of stated as fact.