[texhax] Notation

[Michael Barr]

I would like to second Victor Ivrii's suggestion to restrict all notation 
to a single letter in all its possible fonts, weights and colours.  But in 
deference to Mike Doob's posting perhaps I would stick to "i".  

I checked the oldest book I could find on my shelves that had d(anything), 
which was Agnew's diff eq, vintage 1942, before they deleted the wonderful 
snowplow problem and it used mit d for differentials.  I don't have any 
physics book offhand, but it has been stated that German publishers use 
upright d for differentials.  Maybe they do now, in order to adhere to the 
ISO, but a colleague of mine has a book called "Methoden der Praktischen 
Analysis", published in 1957 by a publisher called G\"oschens.  Just 
opening it up at random, I find d\theta on p. 164 and dt on 165, both in a 
slant font.  But the pi\`ece de r\'esistance is on p. 219 where I find 
this wonderful formula (all d's in the same slant):
$$a_l = {1\over l\pi}\int_0^d f(x)d\left(\sin l{2\pi x\over d}\right);..$$
They are obviously zeroing in on Victor's suggestion without bothering to 
change the font or colour.

Michael