Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Top 10 most common hard skills listed on resumes...
Date: Tue, 27 Aug 2024 17:46:30 -0700
Organization: None to speak of
Lines: 76
Message-ID: <87ttf5cw49.fsf@nosuchdomain.example.com>
References: <vab101$3er$1@reader1.panix.com>
	<vad7ns$1g27b$1@raubtier-asyl.eternal-september.org>
	<vad8lr$1fv5u$1@dont-email.me> <vaf7f0$k51$2@reader1.panix.com>
	<vafgb2$1to4v$2@dont-email.me>
	<92ab79736a70ea1563691d22a9b396a20629d8cf@i2pn2.org>
	<vafim7$1ubg8$1@dont-email.me> <vah4hr$2b9i8$5@dont-email.me>
	<vahngt$2dtm9$1@dont-email.me> <87r0abzcsj.fsf@bsb.me.uk>
	<87seurdqts.fsf@nosuchdomain.example.com> <87frqqyuib.fsf@bsb.me.uk>
	<87a5gxeppa.fsf@nosuchdomain.example.com> <87a5gxzhep.fsf@bsb.me.uk>
MIME-Version: 1.0
Content-Type: text/plain
Injection-Date: Wed, 28 Aug 2024 02:46:30 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="1017e97994ee365b6a0a4b9b05fc05d0";
	logging-data="3351424"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19XVUcdz28bTu4AlcdLzImo"
User-Agent: Gnus/5.13 (Gnus v5.13)
Cancel-Lock: sha1:GDXowZzVgRwdgOM7UaT2Vjj+mZA=
	sha1:kSF9VYVqH89CyroHltJ5oy8Cx7I=
Bytes: 4497

Ben Bacarisse <ben@bsb.me.uk> writes:
> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
[...]
>> 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)
[...]
> 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.

It's likely you have the same documents I have.  And the first one is
searchable (my mistake), while the second is not.

https://comjnl.oxfordjournals.org/content/6/2/134.full.pdf
"The main features of CPL"
985322 bytes, sha1sum b21f12f964aa4145f984c667862548943fdbf864

https://www.ancientgeek.org.uk/CPL/CPL_Elementary_Programming_Manual.pdf
3626287, sha1sum b007dd5e284cd8cf101a475cae2374eb121892c6

Quoting the former:

"""
6. Expressions

There are two possible modes of evaluation of an expression in CPL,
known as the left-hand (LH) and right-hand (RH) modes. All expressions
can be evaluated in RH mode, but only certain kinds of expression are
meaningful in LH mode. When evaluated in RH mode an expression is
regarded as being a rule for the computation of a value (the RH
value). When evaluated in LH mode an expression effectively gives an
address (the LH value): the significance of this is discussed further in
Section 8.
"""

I speculate that the terms "LH value" and "RH value" evolved to
"l-value" and "r-value", and later to "lvalue" and "rvalue".

And quoting <https://www.cl.cam.ac.uk/~mr10/cpl2bcpl.pdf> :

"""
3.1.
Left and Right hand values

In Fortran, function arguments are passed by reference, that is they are
a collection of pointers to the memory locations where the values can be
found. In Algol, the programmer can specify that some arguments are to
be passed by value, the remaining ones being passed by name, a somewhat
subtle mechanism specified in terms of run time copying of the actual
parameters of a call modifying the function body. Strachey coined the
terms Lvalue and Rvalue to describe the kind of value passed by
reference and value parameters, respectively. These terms were derived
from the kind of values needed when evaluating expressions on the left
and right hand sides of assignment commands. Lmode evaluation could be
performed on simple variables, subscripted expressions and, perhaps more
surprisingly, on functions calls.
"""

Christopher Strachey was the primary designer of CPL.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */