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Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
46 lines
1.7 KiB
Plaintext
46 lines
1.7 KiB
Plaintext
;; showadt.hs — `deriving (Show)` on a multi-constructor recursive ADT.
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;; Source: classic exposition example, e.g. Real World Haskell ch.6.
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;;
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;; Exercises Phase 8: `deriving (Show)` on an ADT whose constructors recurse
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;; into themselves; precedence-based paren wrapping for nested arguments;
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;; `print` from the prelude (which is `putStrLn (show x)`).
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(define
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hk-showadt-source
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"data Expr = Lit Int | Add Expr Expr | Mul Expr Expr deriving (Show)\n\nmain = do\n print (Lit 3)\n print (Add (Lit 1) (Lit 2))\n print (Mul (Lit 3) (Add (Lit 4) (Lit 5)))\n")
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(hk-test
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"showadt.hs — main prints three lines"
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(hk-run-io hk-showadt-source)
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(list "Lit 3" "Add (Lit 1) (Lit 2)" "Mul (Lit 3) (Add (Lit 4) (Lit 5))"))
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(hk-test
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"showadt.hs — show Lit 3"
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(hk-deep-force
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(hk-run
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"data Expr = Lit Int | Add Expr Expr | Mul Expr Expr deriving (Show)\nmain = show (Lit 3)"))
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"Lit 3")
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(hk-test
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"showadt.hs — show Add wraps both args"
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(hk-deep-force
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(hk-run
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"data Expr = Lit Int | Add Expr Expr | Mul Expr Expr deriving (Show)\nmain = show (Add (Lit 1) (Lit 2))"))
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"Add (Lit 1) (Lit 2)")
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(hk-test
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"showadt.hs — fully nested Mul of Adds"
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(hk-deep-force
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(hk-run
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"data Expr = Lit Int | Add Expr Expr | Mul Expr Expr deriving (Show)\nmain = show (Mul (Add (Lit 1) (Lit 2)) (Add (Lit 3) (Lit 4)))"))
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"Mul (Add (Lit 1) (Lit 2)) (Add (Lit 3) (Lit 4))")
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(hk-test
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"showadt.hs — Lit with negative literal wraps int in parens"
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(hk-deep-force
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(hk-run
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"data Expr = Lit Int | Add Expr Expr | Mul Expr Expr deriving (Show)\nmain = show (Lit (negate 7))"))
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"Lit (-7)")
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{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}
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