Xref: utzoo comp.text:7815 comp.text.tex:4566 Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!wuarchive!uunet!mcsun!ukc!dcl-cs!aber-cs!athene!pcg From: pcg@cs.aber.ac.uk (Piercarlo Grandi) Newsgroups: comp.text,comp.text.tex Subject: Re: Using TeX for the UNIX man pages Message-ID: Date: 31 Dec 90 15:57:54 GMT References: <1990Dec28.003306.12375@csis.dit.csiro.au> Sender: pcg@aber-cs.UUCP Organization: Coleg Prifysgol Cymru Lines: 70 Nntp-Posting-Host: teachk In-reply-to: ken@csis.dit.csiro.au's message of 28 Dec 90 00:33:06 GMT On 28 Dec 90 00:33:06 GMT, ken@csis.dit.csiro.au (Ken Yap) said: ken> In article : pcg> The virtual device for which by default TeX output is currently pcg> tailored does indeed map most easily onto a high resolution pcg> typesetter, but I think that it is possible to describe to TeX pcg> different output devices. [ ... ] You can do fixed pitch printing pcg> with TeX, both as to fixed width letters and interword and pcg> interline spacing, e.g. for code listings. I reckon that it is time pcg> for TeX to realize its potential as a ditroff, not as a troff tied pcg> to one specific virtual output device to be mapped more or less pcg> neatly onto actual devices. ken> In summary: 1. I do not see that rounding from scaled points to real ken> device resolution is any sort of limitation so I don't see that we have ken> to follow the ditroff path, and 2. Quantizing TeX's spacings requires ken> only some work with fonts and macros. Character substitution should ken> use virtual fonts of course. I think that we have written exactly the same thing here. Haven't we? ken> But here's the gist of my argument: Piercarlo argues about the ken> 1/65k pt resolution of TeX's ideal device as if it were a ken> limitation. Well, it virtually ensures that quantizing will be approximate, even if by very little. 1/65k of a point is an exceedingly fine resolution, and even if the real device resolution is not (as it is *very* rarely) a factor of 1/65k, the resulting error is usually negligible. Ditroff though avoids even this negligible source of errors by being parametric with respect to the actual hirzontal and vertical resolutions of the intended output device, and ensuring that all motions and sizes are in fact even multiples of these resolutions, and by declaring in its output for which resolutions all motions and sizes are meant. ken> In fact since no actual device exists with this resolution, it is ken> misleading to say that TeX is tailored to "one specific virtual ken> output device" A nit: this is is not misleading, it is entirely accurate. The one specific virtual output device is the one for which DVI files are encoded currently; historically, as I remarked (and you repeated), DVU files were tailored not just for 1/65k resolution, but also for the CM font layout (dependent on obscure Stanford conventions), and both the resolution and the font layout had to be mapped onto those for the real device. The recent introduction of virtual fonts has been motivated precisely by the desire to alleviate the font layout mapping problem, to accomodate non CM fonts more easily. Fortunately TeX can be taught about different fonts and to calculate its output so that coordinates are quantized to look good on other, real, devices, thus making it unnecessary to have DVI rounding standards (except if you are, as yopu should not, printing to a real device different from the one for which the DVI file was optimized). ken> In fact, no such device is likely to be made: near beginning of the ken> TeXbook we read that 1/65k pt is a length comparable to the ken> wavelength of light. What about using TeX to drive electron beam chip etching devices? What about a Conway&Mead set of TeX macros? Can silicon TeX compilation be that far off? :-) :-) :-) -- Piercarlo Grandi | ARPA: pcg%uk.ac.aber.cs@nsfnet-relay.ac.uk Dept of CS, UCW Aberystwyth | UUCP: ...!mcsun!ukc!aber-cs!pcg Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk