[% setvar title Data types: Semi-finite (lazy) lists %]

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TITLE

Data types: Semi-finite (lazy) lists

VERSION

  Maintainer: Damian Conway <damian@conway.org>
  Date: 4 Aug 2000
  Last Modified: 18 Sep 2000
  Mailing List: perl6-language@perl.org
  Number: 24
  Version: 2
  Status: Withdrawn

ABSTRACT

This RFC proposes that the right operand of a .. operator may be omitted in a list context, producing a lazily evaluated semi-finite list. It is further proposed that operations on such lists also be carried out lazily.

DESCRIPTION

It is proposed that the right operand of a list context range operation be made optional. If omitted, the resulting range would become semi-infinite:

	for (1..) {
		print "The next number is: $_\n";
	}

	@odds = grep { $_%2 } (1..);

	switch ($n) {
		case [32..]	{ print "Two many characters in filename" }
		case (@odds)	{ print "That's odd!" }
	}

Note that the values in @odds would also be lazily generated (otherwise the grep would never finish).

IMPLEMENTATION

Ask MJD.

REFERENCES

RFC proposing a co-routine mechanism

The thoughts and writings of Mark-Jason Dominus.