Re: Who first invented dotted-item notation?

On Sunday, May 22, 2022 at 10:15:07 AM UTC-7, Christopher F Clark wrote:
> I know the notation from LR(0) machine construction, but also know
> that Gluskhov used it in his solution to NFA construction. Earley
> also used the notation to describe his method if I understand right.
> I'm presuming that there is some first use of the notation. Do we
> know who invented it?


This could be asked in general, for the origin of different notations
used in programming languages and their documentation.


The first use of dot that I know of, similar to an operator, is for structure
reference qualifiers in PL/I, and later adopted by C and others from there.


I always thought that PL/I adopted structures from COBOL, but never
looked up to see how COBOL did it. It seems that COBOL uses AS
for structure references.


As well as I know it, it was Fortran that first introduced variable names
with more than one character, though mathematics still hasn't done that.
(Fortran also uses dot for operators like .AND. and .LT., as in the early
days the character set was restricted.)


In algebra, it is traditional that two variables next to each other are
multiplied, convenient for readers. There needs to be some separator
to indicate when one name ends and the next begins. In some languages,
that can just be space or some non-operator.
[I believe Chris is asking about the specific use of a dot to show the
position in a partially parsed BNF rule.
PL/I copied its structure declarations close to verbatim from Cobol, with level
numbers to show the nesting. It invented . and -> for structures, while
Cobol used "OF" to refer to elements and doesn't have pointers. -John]

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