62 lines
1.5 KiB
Markdown
62 lines
1.5 KiB
Markdown
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# Haskell Map and Set Modeling
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This note covers `36-haskell-map-set-modeling/`, which models release approval policy directly with `Map` and `Set`.
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---
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## 1. Why These Structures Deserve Their Own Example
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Several earlier examples already use `containers`, but only as support code.
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This example makes the data structures themselves the teaching point:
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- `Map` for service ownership and environment access rules, and
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- `Set` for required, supplied, missing, and unexpected approver groups.
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That is a practical step up from list-based toy models.
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---
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## 2. What the Policy Computation Shows
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The report logic uses set operations directly:
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- intersection for required approvers that are valid in the environment,
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- difference for missing approvers, and
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- difference again for unexpected approvers.
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That makes the policy behavior compact and declarative. The code describes the relationships instead of manually looping over lists.
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---
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## 3. Why This Is Good Domain Modeling
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Ownership, access grants, and approval groups are not “just lists”.
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They have semantics:
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- service names map to owner teams,
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- environments map to allowed teams, and
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- approver groups should not contain duplicates.
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Using `Map` and `Set` makes those semantics explicit in the type choices.
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---
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## 4. Commands to Try
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```bash
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cd 36-haskell-map-set-modeling
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nix develop
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cabal run
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cabal run -- api:production:platform,security
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cabal test
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nix build
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./result/bin/mini-access-policy api:production:platform,security
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nix run . -- api:production:platform,security
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nix flake check
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```
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