14 Apr
2007
14 Apr
'07
3:38 a.m.
------------Original Message:
From: "Chuck Guzis" <cclist at sydex.com>
Subject: Re: HP "calculators" (was Re: World's first computer on
ebay!)
On 14 Apr 2007 at 1:34, der Mouse wrote:
Well, and, this is an expression rather than a
statement; you could do
things like R(X+(1->C))->A (somewhat akin to the way C lets you write
a=r[x+(c=1)]) - did any BASICs do that?
AFAIK, none of the usual suspects permit multiple assignments in a
statement. The odd thing is that GWBASIC will pass a statement of
the form X=Y=7, but Y will be 0 and X will be -1 at the conclusion
of execution, regardless of the value of y or x at the beginning.
OTOH, LET X=Y=3 will set both X and Y to 0. GWBASIC is full of
stuff like this.
------------Reply:
Eh???? Did I miss something?
Those are not multiple assignments but very useful logical tests.
If a logical argument is true, it has the numeric value of -1, else 0,
thus, if Y=7 then x= -1 else x= 0, whether you LET it or not, at least
in the BASICs I work in (and even GWBASIC ;-). When you add and
multiply with it, it can be very handy in certain situations.
That's one of the reasons for LET, to avoid the ambiguity of X=Y being
either an assignment or a numeric value.
mike
14 Apr
14 Apr
10:37 a.m.
> The odd thing is that GWBASIC will pass a
statement of the form
> X=Y=7, but Y will be 0 and X will be -1 at the conclusion of
> execution, regardless of the value of y or x at the beginning.
> OTOH, LET X=Y=3 will set both X and Y to 0. GWBASIC is full of
> stuff like this.
Eh???? Did I miss something?
Yes, I think so.
Those are not multiple assignments but very useful
logical tests.
Then why do they change Y?
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10:51 a.m.
On 14 Apr 2007 at 4:38, M H Stein wrote:
------------Original Message:
From: "Chuck Guzis" <cclist at sydex.com>
Subject: Re: HP "calculators" (was Re: World's first computer on
ebay!)
On 14 Apr 2007 at 1:34, der Mouse wrote:
I suspect that maybe you did.
der Mouse said " things like R(X+(1->C))->A ". That looks like a
multiple assignment to me.
I said "X=Y=7" in GWBASIC changes both X and Y the same way
regardless of their initial values. LET X=Y=7 changes them a
different way, regardless of their initial values. If there's a
conditional operator in either of those statements, I can't find it.
Yes, it's true that BASIC doesn't differentiate lexically between the
assignment operator and equality test, but that seems to be unrelated
to the behavior of the two statements I gave. In fact, I don't know
what the operation performed by GWBASIC is in "X=Y=7".
Cheers,
Chuck
Well, and, this is an expression rather than a
statement; you could do
things like R(X+(1->C))->A (somewhat akin to the way C lets you write
a=r[x+(c=1)]) - did any BASICs do that?
AFAIK, none of the usual suspects permit multiple assignments in a
statement. The odd thing is that GWBASIC will pass a statement of
the form X=Y=7, but Y will be 0 and X will be -1 at the conclusion
of execution, regardless of the value of y or x at the beginning.
OTOH, LET X=Y=3 will set both X and Y to 0. GWBASIC is full of
stuff like this.
------------Reply:
Eh???? Did I miss something?
Those are not multiple assignments but very useful logical tests. 
5:32 p.m.
AFAIK, none of the usual suspects permit multiple
assignments in a
statement. The odd thing is that GWBASIC will pass a statement of
the form X=Y=7, but Y will be 0 and X will be -1 at the conclusion
of execution, regardless of the value of y or x at the beginning.
OTOH, LET X=Y=3 will set both X and Y to 0. GWBASIC is full of
stuff like this.
------------Reply:
On Sat, 14 Apr 2007, M H Stein wrote:
Eh???? Did I miss something?
Those are not multiple assignments but very useful logical tests.
If a logical argument is true, it has the numeric value of -1, else 0,
thus, if Y=7 then x= -1 else x= 0, whether you LET it or not, at least
in the BASICs I work in (and even GWBASIC ;-). When you add and
multiply with it, it can be very handy in certain situations.
That's one of the reasons for LET, to avoid the ambiguity of X=Y being
either an assignment or a numeric value.
So, apparently it is parsing it as x = (Y==7);
An alternative to LET is to have different symbols for assignment v
comparison. == , .EQ. etc
I always liked the APL X <- 3,
which also avoids the beginner mistake of 3 = x
7:39 p.m.
On 14 Apr 2007 at 14:32, Fred Cisin wrote:
So, apparently it is parsing it as x = (Y==7);
An alternative to LET is to have different symbols for assignment v
comparison. == , .EQ. etc
Being an old FORTRAN hacker, I have a weakness for .EQ. .NE. .GT.
.GE. .LT. .LE. No special characters; no digraphs to remember--and
no confusion with the assignment operator. Same for .OR. .AND.
.NOT. Some FORTRANs doubled the application of the latter for binary
arithmetic and added .XOR., .SHL. and .SHR. (shift left, shift
right).
There's something to be said for small character sets.
Cheers,
Chuck
9:35 p.m.
On 14 Apr 2007 at 19:57, woodelf wrote:
Chuck Guzis wrote:
Remembering APL di- and tri-graphs was a big struggle for me. Was
there ever a card punch code for APL?
There's something to be said for small
character sets.
No answer ... I guess not. Offhand I like the idea of
'<-'
instead of =. Also 5 or 6 character file names left much to be
improved on.
That's not a FORTRAN limitation! Remember that FORTRAN uses file
numbers, just like,uh--that other languge. Variables *were* limited
to 6 characters, but that restriction was lifted in later versions.
On the other extreme, I remember a gummint project involving about a
thousand GSA programmers and COBOL. Variable names were codified by
a rigidly enforced coding standard--something in the range of 30
characters long. Made for very tiresome reading of code, not to
mention punching. They really drove home the idea that "COBOL is
verbose".
I always liked the CDC SCOPE idea of permanent vs. temporary/local
files. You could have a permanent file with a very long name and any
number of generations. When you wanted to use it, you'd simply
"attach" it to a local file name that was accessible to your
programs. Other pernanent files weren't accessible to your programs
unless specifically "attached". Anything not specifically attached
to a permanent file or having a predefined disposition (e.g. OUTPUT,
PUNCH) was treated as a scratch file and discarded at job
termination.
The version idea was pretty neat--you normally would work with the
latest version of the file, but you could specify an earlier version
if desired.
Cheers,
Chuck
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