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[Density?] SEQUENCE-FUNCTIONS-EXCLUDE-ARRAYS (Version 4)
- To: labrea!Moon%STONY-BROOK.SCRC.Symbolics.COM@labrea.stanford.edu
- Subject: [Density?] SEQUENCE-FUNCTIONS-EXCLUDE-ARRAYS (Version 4)
- From: Jon L White <firstname.lastname@example.org>
- Date: Mon, 7 Dec 87 18:22:31 PST
- Cc: email@example.com
- In-reply-to: David A. Moon's message of Mon, 30 Nov 87 12:19 EST <19871130171930.3.MOON@EUPHRATES.SCRC.Symbolics.COM>
re: It [density] can also be deduced from the definitions of array-total-size
and array-row-major-index, because the range of array-row-major-index's
answer is defined to be a range of integers that contains just enough
members to supply a value for each subscript set, with no gaps.
I think my previous note mentioned that density in storage isn't actually
required by this bijective mapping -- it would only do so if the output
of array-row-major-index were required to be a memory index.
Perhaps one couldn't imagine any other meaning for array-row-major-index
other than "index offset from base memory location"; but CLtL doesn't
say this now, and I can certainly think of alternative representations
which would reinject the "linearized" index into the multi-dimensional
format simply in order to preserve the documented property.
If any clarification is necessary, then it ought to take into account
the AREF-1D proposal, which would raise some efficiency questions if the
bijective mapping weren't "index-offset" memory access.
-- JonL --