tuple.eo

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+architect yegor256@gmail.com
+home https://github.com/objectionary/eo
+package org.eolang
+rt jvm org.eolang:eo-runtime:0.0.0
+version 0.0.0

# Tuple.
[head tail] > tuple
  # Empty tuple.
  [] > empty
    # Take one element from the tuple, at the given position.
    [i] > at
      error "Can't get an object from the empty tuple" > @
    # Take one element from the tuple, at the given position.
    [x] > with
      tuple > @
        tuple.empty
        x
    0 > length

  # Obtain the length of the tuple.
  [] > length!
    ^.head.length.plus 1 > @

  # Take one element from the tuple, at the given position.
  [i] > at
    i > idx!
    ^.length > len!
    if. > index!
      idx.lt 0
      len.plus idx
      idx
    if. > @
      or.
        index.lt 0
        index.gte len
      error "Given index is out of tuple bounds"
      at-without-checks index

    # Takes element from the tuple without index validation.
    # Here i must be an object that can be comparable with int using lt attribute.
    [i] > at-without-checks
      i > idx!
      if. > @
        idx.lt head.length
        ^.^.head.at.at-without-checks idx
        ^.^.tail

  # Create a new tuple with this element added to the end of it.
  [x] > with
    tuple > @
      ^
      x