79 lines
1.8 KiB
Nim
79 lines
1.8 KiB
Nim
import std/[options, os, sugar]
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# Declarations
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type
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Error* = enum OK, ERR
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FileDesc* = enum STDIN, STDOUT, STDERR
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IO*[T] = proc(): T
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func fileread*(file: string): IO[Option[string]]
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func filewrite*(data: string, file: string): IO[Error]
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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[T], fn: T -> U): IO[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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# Unsafe
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proc read_unsafe(file: string): Option[string] =
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try:
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let data: string = readFile(file)
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some(data)
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except IOError:
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none(string)
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proc write_unsafe(data: string, file: string): Error =
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try:
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writeFile(file, data)
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OK
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except IOError:
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ERR
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# Definitions
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func fileread*(file: string): IO[Option[string]] =
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proc(): Option[string] =
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if fileExists(file):
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read_unsafe(file)
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else:
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none(string)
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func filewrite*(data: string, file: string): IO[Error] =
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proc(): Error = write_unsafe(data, file)
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func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U] = join(map(io, 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] = map(io, run)
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func map*[T, U](io: IO[T], fn: T -> U): IO[U] =
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proc(): U = fn(run(io))
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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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