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95 lines
2.1 KiB
Nim
95 lines
2.1 KiB
Nim
discard """
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action: compile
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"""
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# bug #3313
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import unittest, sugar
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{.experimental: "notnil".}
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type
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ListNodeKind = enum
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lnkNil, lnkCons
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List*[T] = ref object
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## List ADT
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case kind: ListNodeKind
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of lnkNil:
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discard
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of lnkCons:
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value: T
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next: List[T] not nil
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proc Cons*[T](head: T, tail: List[T]): List[T] =
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## Constructs non empty list
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List[T](kind: lnkCons, value: head, next: tail)
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proc Nil*[T](): List[T] =
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## Constructs empty list
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List[T](kind: lnkNil)
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proc head*[T](xs: List[T]): T =
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## Returns list's head
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xs.value
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# TODO
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# proc headOption*[T](xs: List[T]): Option[T] = ???
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proc tail*[T](xs: List[T]): List[T] =
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## Returns list's tail
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case xs.kind
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of lnkCons: xs.next
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else: xs
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proc isEmpty*(xs: List): bool =
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## Checks if list is empty
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xs.kind == lnkNil
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proc `==`*[T](xs, ys: List[T]): bool =
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## Compares two lists
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if (xs.isEmpty, ys.isEmpty) == (true, true): true
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elif (xs.isEmpty, ys.isEmpty) == (false, false): xs.head == ys.head and xs.tail == ys.tail
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else: false
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proc asList*[T](xs: varargs[T]): List[T] =
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## Creates list from varargs
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proc initListImpl(i: int, xs: openArray[T]): List[T] =
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if i > high(xs):
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Nil[T]()
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else:
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Cons(xs[i], initListImpl(i+1, xs))
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initListImpl(0, xs)
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proc foldRight*[T,U](xs: List[T], z: U, f: (T, U) -> U): U =
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case xs.isEmpty
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of true: z
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else: f(xs.head, xs.tail.foldRight(z, f))
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proc dup*[T](xs: List[T]): List[T] =
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## Duplicates the list
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xs.foldRight(Nil[T](), (x: T, xs: List[T]) => Cons(x, xs))
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type
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ListFormat = enum
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lfADT, lfSTD
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proc asString[T](xs: List[T], f = lfSTD): string =
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proc asAdt(xs: List[T]): string =
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case xs.isEmpty
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of true: "Nil"
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else: "Cons(" & $xs.head & ", " & xs.tail.asAdt & ")"
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proc asStd(xs: List[T]): string =
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"List(" & xs.foldLeft("", (s: string, v: T) =>
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(if s == "": $v else: s & ", " & $v)) & ")"
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case f
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of lfADT: xs.asAdt
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else: xs.asStd
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proc `$`*[T](xs: List[T]): string =
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## Converts list to string
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result = xs.asString
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proc foldLeft*[T,U](xs: List[T], z: U, f: (U, T) -> U): U =
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case xs.isEmpty
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of true: z
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else: foldLeft(xs.tail, f(z, xs.head), f)
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