Re: Top 10 most common hard skills listed on resumes...

Tim Rentsch <tr.17687@z991.linuxsc.com> writes:

Ben Bacarisse <ben@bsb.me.uk> writes:
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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
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Ben Bacarisse <ben@bsb.me.uk> writes:
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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
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Ben Bacarisse <ben@bsb.me.uk> writes:
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Bart <bc@freeuk.com> writes:
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BLISS is a rather strange language.  For something supposedly
low level than C, it doesn't have 'goto'.
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It is also typeless.
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There is also a key feature that sets it apart from most HLLs:
usually if you declare a variable A, then you can access A's
value just by writing A;  its address is automatically
dereferenced.

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Not always.  This is where left- and right-evaluation came in.
On the left of an assignment A denotes a "place" to receive a
value.  On the right, it denotes a value obtained from a place.
CPL used the terms and C got them via BCPL's documentation.
Viewed like this, BLISS just makes "evaluation" a universal
concept.

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As I recall, the terms "lvalue" and "rvalue" originated with CPL.
The 'l' and 'r' suggest the left and right sides of an
assignment.
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Disclaimer:  I have a couple of CPL documents, and I don't see
the terms "lvalue" and "rvalue" in a quick look.  The PDFs are
not searchable.  If someone has better information, please post
it.  Wikipedia does say that the notion of "l-values" and
"r-values" was introduced by CPL.

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I presume, since I mentioned the concepts coming from CPL, you are
referring to specifically the short-form terms l- and r-values?
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I can't help with those specific terms as the document I have uses
a mixture of terms like "the LH value of...", "left-hand
expressions" and "evaluated in LH mode".

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The documents I have are unsearchable PDFs;  they appear to be
scans of paper documents.
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https://comjnl.oxfordjournals.org/content/6/2/134.full.pdf
https://www.ancientgeek.org.uk/CPL/CPL_Elementary_Programming_Manual.pdf
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Do you have friendlier documents?

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The earliest that is searchable has this title page:
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  UNIVERSITY OF LONDON INSTITUTE OF COMPUTER SCIENCE
  *************************************************
  THE UNIVERSITY MATHEMATICAL LABORATORY, CAMBRIDGE
  *************************************************
  CPL ELEMENTARY PROGRAMMING MANUAL
  Edition I (London)
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  This document, written by the late John Buxton, was preserved by
  Bill Williams, formerly of London University?s Atlas support team.
  Bill has generously made it available to Dik Leatherdale who has
  OCRed and otherwise transcribed it for the Web.  All errors should
  be reported to dik@leatherdale.net.  The original appearance is
  respected as far as possible, but program text and narrative are
  distinguished by the use of different fonts.  Transcriber's
  additions and 'corrections' are in red, hyperlinks in underlined
  purple.  A contents list and a selection of references have been
  added inside the back cover.
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  March 1965
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I don't know where I got it from.  The other searchable one is just
a PDF is the oft-cited paper "The main features of CPL" by Barron
et. al.

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My understanding is the terms l-value and r-value, along with
several other terms widely used in relation to programming
languages, became widely used following a summer(?) course taught
by Christopher Strachey.  Some of the other terms are referential
transparency and parametric polymorphism, IIRC.

The earlier ('65 and '66) writings about CPL that I've seen all use the
longer terms, and those lectures certainly use the short forms, so it
seems clear this is when they came about and, since he is the sole
author of the notes (unlike all the CPL documents that are groups
efforts), it's also likely he invented the terms.

https://en.wikipedia.org/wiki/Fundamental_Concepts_in_Programming_Languages
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I believe it is possible to track down the notes from that course,
if a diligent web search is employed.  I remember reading a copy
some years ago after finding one on the internet.

I suspect there is no copyright-free PDF as the notes were published by
an academic press.

None the less well worth a read, even nearly 60 years later.  Is it a
shame that that is the case?

--
Ben.