## Chapter 9 — Four shared values become three valid ### Lesson map Lesson 09. Map, example, EX055. ```mermaid flowchart TD F["Four shared tuples"] --> R["One rejected"] R --> V["valid length 3"] V --> Q{"Does 3 mean three shareable values?"} Q -->|No| K["AMBER is still inside valid"] ``` The count is the length of `valid`. Sharing is a later filter. ### Logical drawing ```text shared, in written order donate-elmfield.example 198.51.100.400 elmfield-giftaid.example 203.0.113.9 rejected 198.51.100.400 remaining in valid the other three, including AMBER ``` ### Learning outcomes After this chapter, you should be able to: 1. Count the shared tuples and the rejected one. 2. Read `valid: 3` as a length. 3. Refuse the claim that all three are community material. ### 9.1 The length includes the AMBER domain. It excludes only the rejected address. `shared` has four pairs. The loop appends a pair to `valid` when the value is kept, and it `continue`s past `198.51.100.400` after printing `invalid:`. Three pairs remain, so `print("valid:", len(valid))` writes `valid: 3`. That integer is a length. It is not a list of names, and it is not a count of community items. The three kept pairs are `donate-elmfield.example` with `TLP:GREEN`, `elmfield-giftaid.example` with `TLP:AMBER`, and `203.0.113.9` with `TLP:CLEAR`. The AMBER pair is inside `valid`. A sentence that reads `valid: 3` as "three things EFBN may send to CCC" has skipped the label. The community filter runs later and drops AMBER. The length line has already been printed by then, and it does not change. The rejected address is absent from the length. It cannot be one of the three. Quoting `valid: 3` beside the invalid line is consistent: four minus one. | Figure | Meaning | |---|---| | 4 shared pairs | The input list | | `invalid:` one value | Removed before the length | | `valid: 3` | Length of what remained | | Community permission | Not this integer | ### 9.2 Worked example | Offered sentence | Arithmetic | Decision | |---|---|---| | "Four pairs in, one rejected, length 3." | The loop | Keep | | "The AMBER domain is one of the three." | It was appended | Keep | | "valid: 3 means three shareable indicators." | The filter has not run | Refuse | | "The invalid address is included in the 3." | `continue` skipped it | Refuse | > **Synthetic case.** The length line is one integer. ### Errors and limits Do not spend the integer as if it were a permission. ### Apply - **EX055 — The integer.** What does `valid: 3` count, and is the AMBER domain inside that count? *Rubric:* 3 = three kept pairs; the invalid address is excluded; the AMBER domain is included; the integer is not the community list;; 2 = length 3 includes AMBER and excludes the invalid address;; 1 = the digit only;; 0 = none. ### Continue studying — lesson 09 (chapter 09 of 20) [← Chapter 08](#ch-08) · [Course chapter index](../SUBJECTS.md) · [Chapter 10 →](#ch-10) Continue to the next authored lesson. ## Worked answers **EX055.** `valid: 3` counts three kept pairs. The invalid address is excluded. The AMBER domain is included. The integer is not the community list.