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What's the meaning of "**" ?

 

Hello,
in some models I found some double "*": what's the meaning of this operator ?
Thanks a lot in advance.
 

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On 21/03/2025 18:01, pilou via groups.io wrote:
in some models I found some double "*": what's the meaning of this operator ?
"**" is the exponentiation operator.

See, e.g.: Help > LTspice > LTspice? > Circuit Elements >B. Arbitrary Behavioral Voltage or Current Sources > The following functions table (near the bottom).

--
Regards,
Tony
 

"a**b" means a raised to the power (or exponent) b.
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"a^b" does?not mean the same thing, but with one exception.
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IIRC, "**" is from the days of FORTRAN, or earlier.
?
Andy
 

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You recall correctly:

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** was first used in Fortran, which first appeared in 1957

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From: [email protected] <[email protected]> On Behalf Of Andy I via groups.io
Sent: Friday, March 21, 2025 10:16 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] What's the meaning of "**" ?

?

"a**b" means a raised to the power (or exponent) b.

?

"a^b" does?not mean the same thing, but with one exception.

?

IIRC, "**" is from the days of FORTRAN, or earlier.

?

Andy
 

Hello to all,
thanks a lot for your reply.
 

The ^ operator can be used to implement exponentiation in Laplace expressions in the behavioral sources. Otherwise it is the exclusive OR operator.
 

The FORTRAN character set had fewer characters and predated ASCII by five years or so.
 

FORTRAN first appeared on the IBM 704 mainframe in the 1950s. IBM (and many other manufacturers at that time) used various versions of the 6-bit BCDIC (Binary-Coded-Decimal Interchange Code) at that time. Of the 64 possible combinations only 48 represented printable characters, which were:
?
The numbers 0 - 9;
The upper-case letters A - Z
Punctuation characters [space] = - + . ) - $ * , ( /
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Yes, there were two instances of the hyphen/minus character! This is quoted from the IBM 704 Fortran Programmer's Reference Manual dated October 1956, which lists character encoding for punched-cards, mag. tape and the 704 internal code.
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It was based on the existing character set encoding widely used on punched cards, which was the major form of source code/data input into mainframes at the time (I remember it well!). In the 1960s, IBM developed the 128-bit EBCDIC (Extended BCDIC) character set for their System/360 machines, pretty much contemporaneously with the ASCII standard development.
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?
?
 

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Just to add a little more background, Burroughs also used EBCDIC for a while. The B6700 I had access to in the early to mid 70s at University had EDCDIC available although the preferred character set on that machine was ASCII. They even had ROM modules to perform character conversions between the two character sets in a single clock cycle. Doesn't sound very impressive now but it was back then.

Paul Wilson

On 22/03/2025 00:53, martin.sadler via groups.io wrote:

FORTRAN first appeared on the IBM 704 mainframe in the 1950s. IBM (and many other manufacturers at that time) used various versions of the 6-bit BCDIC (Binary-Coded-Decimal Interchange Code) at that time. Of the 64 possible combinations only 48 represented printable characters, which were:
?
The numbers 0 - 9;
The upper-case letters A - Z
Punctuation characters [space] = - + . ) - $ * , ( /
?
Yes, there were two instances of the hyphen/minus character! This is quoted from the IBM 704 Fortran Programmer's Reference Manual dated October 1956, which lists character encoding for punched-cards, mag. tape and the 704 internal code.
?
It was based on the existing character set encoding widely used on punched cards, which was the major form of source code/data input into mainframes at the time (I remember it well!). In the 1960s, IBM developed the 128-bit EBCDIC (Extended BCDIC) character set for their System/360 machines, pretty much contemporaneously with the ASCII standard development.
?
?
?
 

On Sat, Mar 22, 2025 at 03:01 AM, <martin.sadler@...> wrote:
Yes, there were two instances of the hyphen/minus character!
I am not a linguist, but actually there are a few, and I am surely guilty of misusing them.? A minus sign and a hyphen are not supposed to be interchangeable.
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This caused a problem when LTspice IV (?) first came out with Unicode, because Unicode added even more characters that look similar but are not.? We ran into cases where something that looked like a minus sign was actually a new Unicode character that got mixed in among the regular ANSI characters (in some text from a magazine article), and they used it as a subtraction (minus) character, but LTspice did not recognize it as such and the math formula could not be evaluated.
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Mike Engelhardt needed to add more "exceptions" to the Unicode character handling.
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Andy
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