## Chapter 11 — Hits follow the mail list ### Lesson map Lesson 11. Map, example, EX057. ```mermaid flowchart TD M["Three mail rows, written order"] --> S["Membership in the valid set"] S --> H["Two tuples, mail order"] H --> Q{"Did the shared-list order win?"} Q -->|No| K["vol-07 then office"] ``` The set answers yes or no. The mail list chooses the sequence. ### Logical drawing ```text mail order vol-07, donate-elmfield.example vol-12, news.example office, elmfield-giftaid.example printed hits vol-07 then office not a sort key the order of shared ``` ### Learning outcomes After this chapter, you should be able to: 1. Read the hit list as mail order. 2. Say what the set is used for. 3. Refuse a hit line that starts with the office. ### 11.1 Membership does not reorder. The comprehension walks `mail`. The hit line keeps a mail row when its domain or address is a member of the set of valid values. A set has no order, so it cannot be the sequence of the result. The comprehension walks `mail` from top to bottom. `vol-07` is first and matches, `vol-12` is second and does not match, and `office` is third and matches. The printed list is therefore vol-07, then office. `news.example` never becomes a tuple in that list. `shared` listed the GREEN domain first and the AMBER domain later. That writing order is not the hit order, even though both names match. Swapping the hit tuples to follow `shared` would be a different list. The print uses Python's representation of a list of tuples, with single quotes and the parentheses. Those marks are the representation, not extra evidence. | Choice | Source | |---|---| | Which rows qualify | Set membership | | Which qualified row prints first | Position in `mail` | | Whether vol-12 appears | It does not qualify | | Shared-list order | Not the hit sequence | ### 11.2 Worked example | Offered order | Why it is or is not the print | Decision | |---|---|---| | vol-07 then office | Mail order, with the miss skipped | Keep | | Both qualifying names present | Their rows matched | Keep | | "Office first, because AMBER is more sensitive." | No severity sort | Refuse | | "The hits follow the shared list." | The walk is `mail` | Refuse | > **Synthetic case.** The hit list has two tuples. ### Errors and limits Do not let a label's seriousness reorder the mail walk. ### Apply - **EX057 — Hit order.** The print lists vol-07 and then office. Does that order come from `shared`, and where is `news.example`? *Rubric:* 3 = the order is the mail list; the set only tests membership; news.example is a mail row that does not qualify; do not sort by label;; 2 = mail order, and the third row is not a hit;; 1 = one tuple;; 0 = none. ### Continue studying — lesson 11 (chapter 11 of 20) [← Chapter 10](#ch-10) · [Course chapter index](../SUBJECTS.md) · [Chapter 12 →](#ch-12) Continue to the next authored lesson. ## Worked answers **EX057.** The order is the mail list. The set only tests membership. `news.example` is a mail row that does not qualify. Do not sort by label.