61 lines
1.4 KiB
Nim
61 lines
1.4 KiB
Nim
import std/sugar
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# Declarations
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type
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FileDesc* = enum STDIN, STDOUT, STDERR
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IO*[T] = proc(): T
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func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U]
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func lift*(fn: proc(): void): IO[void]
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func lift*[T](fn: proc(): T): IO[T]
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func join*[T](io: IO[IO[T]]): IO[T]
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func map*[T, U](io: IO[seq[T]], fn: T -> U): IO[seq[U]]
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func readstr*(stream: FileDesc): IO[string]
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func run*[T](io: IO[T]): T
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func strput*(str: string): IO[void]
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func to_IO*[T](val: T): IO[T]
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# Definitions
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func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U] = join(io.map(fn))
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func lift*(fn: proc(): void): IO[void] =
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proc(): void = fn()
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func lift*[T](fn: proc(): T): IO[T] =
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proc(): T = fn()
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func join*[T](io: IO[IO[T]]): IO[T] = io.map(run)
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func map*[T, U](io: IO[seq[T]], fn: T -> U): IO[seq[U]] =
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proc(): seq[U] =
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let list: seq[T] = io()
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if list.len == 0:
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@[]
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else:
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let
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head: T = list[0]
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tail: seq[T] = list[1..^1]
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new: IO[seq[T]] = to_IO tail
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@[fn(head)] & run new.map(fn)
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func readstr*(stream: FileDesc): IO[string] =
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case stream:
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of STDIN:
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lift proc(): string = readLine(stdin)
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of STDOUT:
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lift proc(): string = readLine(stdout)
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of STDERR:
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lift proc(): string = readLine(stderr)
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func run*[T](io: IO[T]): T = io()
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func strput*(str: string): IO[void] =
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proc(): void = echo str
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func to_IO*[T](val: T): IO[T] =
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proc(): T = val
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