[pstricks] not backwards compatible

[Michael Sharpe]

Backwards compatibility is a fine goal, but may not be truly possible.  
Bugs cannot always be fixed and improvements cannot always be  
constructed without side effects, especially in a language as singular  
as TeX. With the changes over the years in TeX, TeX fonts and their  
metrics, style files and all the rest, practically nothing I wrote in  
TeX over 20 years ago comes out exactly the same when processed now.  
For example, I wrote a book in the mid 80's that is now out of print,  
and I am unable to duplicate the page layout of the original---it used  
the Almost Modern fonts and the original AMSTeX 1.0, none of which I  
can duplicate exactly now.

In generating and saving graphics, my experience is that the eps  
format is the most unchanged over the last 20 years. I save all  
PTricks output as eps as well as pdf, so that I can at the very least  
edit the eps file with a tool like Adobe Illustrator, making use of  
psfrag if necessary to substitute the font or wording of labels, even  
if the original pstricks document produces different output than it  
did originally.

I remember how exciting it was when the original PSTricks appeared,  
and thanks to the continuing work of Herbert and other experts, it  
continues to be a most useful tool for mathematical illustration.

Michael