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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: Which code style do you prefer the most?
Date: Fri, 7 Mar 2025 15:37:12 +0100
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On 06/03/2025 22:14, Kaz Kylheku wrote:
> On 2025-03-06, Richard Heathfield <rjh@cpax.org.uk> wrote:
>> At school we used a, b, c... for trigonometry and p, q, r for
>> point co-ordinates, so I suppose I assumed that i, j, k... for
>> matrices was intended to exploit a nice juicy part of the
>> alphabet that wasn't being used for anything else...
>>
>> ...and then along came imaginary numbers.
> 
> The imaginary i happily coexists with the indexing i.

Yes.

> 
> Mathematicians come in two varieties: those who are oblivious
> to ambiguity and those who relish it. This i situation goes
> unnoticed by the former, and pleases the latter.
> 

Mathematicians come in two varieties - those that can count, and those 
that can't count.

In my mathematics, I neither relish ambiguity nor am I oblivious to it - 
and I think most mathematicians are like that.

It is almost always obvious from context whether "i" refers to the 
imaginary number constant, or a counter index.  In situations where both 
might be used (such as the summation for a Fourier series), you simply 
use a different letter for the index - j, k, and n are typical.

> Electrical engineers, on the other hand, came along bearing
> current, and immediately saw the i clash, renaming the
> imaginary i to j.
> 

I've done plenty of electronics design, though I have no formal 
education in electrical engineering.  But I think it is quite common to 
use imaginary "i" rather than "j" - it's usually obvious from the 
context when you are talking about a current.  It's rare that you only 
have one current of interest in a system, so you already have i1, i2, 
i_in, i_out, or whatever.  There is rarely a clash.

> However, electrical engineers don't count through any abstract spaces,
> so they don't care about i (current) clashing with i (indexing).
> 

Of course electrical engineers count loops.

> They count things like resistors (R1, R2, ...), capacitors (C1, C2, ...)
> integrated circuits (U1, U2, ...), component pins, and so on.
> 

And they loop through these things - consider multi-stage filters, 
transmission line models, etc.

> An EE would never say impractical, goofy things like, "For i from 1
> through n (that being the number of capacitors n in my circuit), such
> and such a facts holds about Ci ..."
> 

They could quite happily talk about the sum of load capacitors C_i on a bus.