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55 lines
1.6 KiB
Text
55 lines
1.6 KiB
Text
app "example"
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packages {
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cli: "https://github.com/roc-lang/basic-cli/releases/download/0.9.1/y_Ww7a2_ZGjp0ZTt9Y_pNdSqqMRdMLzHMKfdN8LWidk.tar.br",
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parser: "https://github.com/lukewilliamboswell/roc-parser/releases/download/0.5.2/9VrPjwfQQ1QeSL3CfmWr2Pr9DESdDIXy97pwpuq84Ck.tar.br",
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}
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imports [
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cli.Stdout,
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cli.Stderr,
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parser.Core.{ Parser, buildPrimitiveParser, many },
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parser.String.{ parseStr },
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]
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provides [main] to cli
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main =
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lettersInput = "AAAiBByAABBwBtCCCiAyArBBx"
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ifLetterA = \l -> l == A
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when parseStr (many letterParser) lettersInput is
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Ok letters ->
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letters
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|> List.keepIf ifLetterA
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|> List.map \_ -> 1
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|> List.sum
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|> Num.toStr
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|> \countLetterA -> Stdout.line "I counted $(countLetterA) letter A's!"
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Err _ -> Stderr.line "Ooops, something went wrong parsing letters"
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Letter : [A, B, C, Other]
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letterParser : Parser (List U8) Letter
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letterParser =
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input <- buildPrimitiveParser
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valResult =
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when input is
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[] -> Err (ParsingFailure "Nothing to parse")
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['A', ..] -> Ok A
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['B', ..] -> Ok B
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['C', ..] -> Ok C
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_ -> Ok Other
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valResult
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|> Result.map \val -> { val, input: List.dropFirst input 1 }
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expect
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input = "B"
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parser = letterParser
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result = parseStr parser input
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result == Ok B
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expect
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input = "BCXA"
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parser = many letterParser
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result = parseStr parser input
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result == Ok [B, C, Other, A]
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