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From a Pile of Conditionals to Readable Design: Switches, Flag Parameters and Rule Tables

There is no single right target for nested conditionals: polymorphism is cheaper when new types arrive often, a switch expression when new operations do, and a rule table when rules change often and share one shape. The post turns PricingEngine's discount conditionals into all three targets through the same 144-combination snapshot, with an enum, guard clauses, a split flag parameter and a Percentage type, and shows real CS8509, CS0535 and missing-rule test output.