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validate_int returns Left msg on empty / non-digit, Right
(int_of_string s) on a digit-only string. process folds inputs with a
tuple accumulator (errs, sum), branching on the result.
['12'; 'abc'; '5'; ''; '100'; 'x']
-> 3 errors (abc, '', x), valid sum = 12+5+100 = 117
-> errs * 100 + sum = 417
Exercises:
- Either constructors used bare (Left/Right without 'Either.'
qualification)
- char range comparison: c >= '0' && c <= '9'
- tuple-pattern destructuring on let-binding (iter 98)
- recursive helper defined inside if-else
- List.fold_left with tuple accumulator
36 baseline programs total.
25 lines
605 B
OCaml
25 lines
605 B
OCaml
let validate_int s =
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if String.length s = 0 then Left "empty"
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else
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let rec all_digits i =
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if i >= String.length s then true
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else
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let c = s.[i] in
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if c >= '0' && c <= '9' then all_digits (i + 1)
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else false
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in
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if all_digits 0 then Right (int_of_string s)
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else Left ("not a number: " ^ s)
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let process inputs =
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List.fold_left (fun (errs, vals) s ->
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match validate_int s with
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| Left _ -> (errs + 1, vals)
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| Right v -> (errs, vals + v)
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) (0, 0) inputs
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;;
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let (errs, sum) = process ["12"; "abc"; "5"; ""; "100"; "x"] in
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errs * 100 + sum
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