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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: Top 10 most common hard skills listed on resumes...
Date: Tue, 27 Aug 2024 18:19:39 -0700
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Ben Bacarisse <ben@bsb.me.uk> writes:

> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>
>> Ben Bacarisse <ben@bsb.me.uk> writes:
>>
>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>>
>>>> Ben Bacarisse <ben@bsb.me.uk> writes:
>>>>
>>>>> Bart <bc@freeuk.com> writes:
>>>>>
>>>>>> BLISS is a rather strange language.  For something supposedly
>>>>>> low level than C, it doesn't have 'goto'.
>>>>>>
>>>>>> It is also typeless.
>>>>>>
>>>>>> 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.
>>>>>
>>>>> 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.
>>>>
>>>> As I recall, the terms "lvalue" and "rvalue" originated with CPL.
>>>> The 'l' and 'r' suggest the left and right sides of an
>>>> assignment.
>>>>
>>>> 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.
>>>
>>> I presume, since I mentioned the concepts coming from CPL, you are
>>> referring to specifically the short-form terms l- and r-values?
>>>
>>> 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".
>>
>> The documents I have are unsearchable PDFs;  they appear to be
>> scans of paper documents.
>>
>> https://comjnl.oxfordjournals.org/content/6/2/134.full.pdf
>> https://www.ancientgeek.org.uk/CPL/CPL_Elementary_Programming_Manual.pdf
>>
>> Do you have friendlier documents?
>
> The earliest that is searchable has this title page:
>
>   UNIVERSITY OF LONDON INSTITUTE OF COMPUTER SCIENCE
>   *************************************************
>   THE UNIVERSITY MATHEMATICAL LABORATORY, CAMBRIDGE
>   *************************************************
>   CPL ELEMENTARY PROGRAMMING MANUAL
>   Edition I (London)
>
>   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.
>
>   March 1965
>
> 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.

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.

https://en.wikipedia.org/wiki/Fundamental_Concepts_in_Programming_Languages

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.