From 666d182813e8888d3eacbc534c0e403977d3ad6d Mon Sep 17 00:00:00 2001 From: Benjamin Kietzman Date: Thu, 29 Aug 2019 10:00:23 -0400 Subject: [PATCH] add documentation on interpretation of null slots --- docs/source/format/Columnar.rst | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/docs/source/format/Columnar.rst b/docs/source/format/Columnar.rst index 57a1087faf9..0e6ac49fd54 100644 --- a/docs/source/format/Columnar.rst +++ b/docs/source/format/Columnar.rst @@ -214,6 +214,14 @@ value; any "masked" memory can have any value and need not be zeroed, though implementations frequently choose to zero memory for null values. +Null slots should be interpreted as unknowns. Thus if and only if an +expression referencing an array slot would evaluate identically for +every possible value of that slot then the expression's value is well +defined even if the array slot is null. For example, +``(slot 0 of [null, true, false]) AND false`` should evaluate to +``false``, since ``x AND false`` evaluates to ``false`` for all +possible boolean values of ``x``. + Fixed-size Primitive Layout ---------------------------