On Mon, May 12, 2014 at 11:39:40PM -0700, William "Chops" Westfield wrote:
> >  the let statement seemed pretty stupid.
>=20

> Yes.  Yet I've heard various respectable CS types claim that NOT having a
> separate and explicit assignment operator/statement causes computer
> languages to be "confusing" to mathematicians, because of course in
> Mathematics, a statement like "a =3D a+1" can never be true.  Thus ":=3D"=
 in
> Pascal, backward-arrow in APL, and etc.

> Wikipedia has the details: http://en.wikipedia.org/wiki/Assignment_%28com=
puter_science%29

That may or may not have been the initial impetus. A much simpler
explanation is that LET was a keyword that facilitated knowing what should
come next, therefore simplying the process of parsing the statement. As a
language designer, it's pretty easy for me to see that the statement:

A =3D 3

would require scanning through all possible keywords, reaching the end of
the list, then deciding it must be a variable and then it's an assignment
statement. Whereas:

LET A =3D 3

is keyworded with a specific keyword which is easy to find and defines the
semantics of the statement.

Parsing the latter is much easier.

BAJ

>=20
> BillW
>=20
>=20
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Byron A. Jeff
Chair: Department of Computer Science and Information Technology
College of Information and Mathematical Sciences
Clayton State University
http://faculty.clayton.edu/bjeff
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