Patches item #469, was opened at 2006-01-12 01:39
Status: Closed Priority: 3 Submitted By: Morten Høgholm (morten) Assigned to: The Thanh Han (hanthethanh) Summary: \currentexpansionmode + \ifalignscanning - \ifinedef Category: Primitives Group: v1.40.0 Resolution: Rejected
Initial Comment: Here's a patch made against pdftex-1.40.0-alpha-20060111. It removes the \ifinedef primitive for a different primitive, namely \currentexpansionmode. This read-only register is 0 when doing regular typesetting, 1 when inside \edef or \xdef and 2 in other cases of full expansion with scan_toks. It could possibly be extended to distinguish between \marks and \write etc. Comments more than welcome on this one! I have also added an \ifalignscanning test. It is true whenever TeX is looking for \noalign etc. so is most useful for a \stopalignscanning function defined as \def\stopalignscanning{\ifalignscanning\relax\fi} ---------------------------------------------------------------------- Comment By: Frank Mittelbach (mittelbach) Date: 2006-02-15 17:38 Message: Logged In: YES user_id=3421 concerning register versus individual \if... primitves: I agree that numeric values are less easy to read but if the numeric codes are well chosen then they have the advantage of not cluttering the code, eg if you have to test for a number of different cases then a set of nested \if's is also not really helpful. Suppose for example you have to do different actions depending on the type of expansion. Then the register allows you to do this in a since \ifcase or in some \ifnum ...> . But of course this only works is the order is adjusted to typical usages. And non-numerical ones could still be implemented efficently at the macro level, eg \def\ifinedef{\ifnum 1=\currentexpansionmode} as to \stopalignscanning: this is not identical to \protected as protection prevents expansion in all cases which is not necessarily what you need my 2 cents frank ---------------------------------------------------------------------- Comment By: Hans Hagen (hagen) Date: 2006-01-17 22:22 Message: Logged In: YES user_id=927 concerning alignments: - how about adding \everyaligncell (in addition to \everycr) - how about the other iftests? - (and \nospan -) ---------------------------------------------------------------------- Comment By: Morten Høgholm (morten) Date: 2006-01-16 20:23 Message: Logged In: YES user_id=3333 @None: An \ifalignscanning primitive can also help macros like LaTeX's \multicolumn and other code that relies on seeing \noalign or \omit to recover gracefully with a comprehensible error message. ---------------------------------------------------------------------- Comment By: Morten Høgholm (morten) Date: 2006-01-13 04:50 Message: Logged In: YES user_id=3333 Yes, just ideas here, which is why I asked for comments. We can discuss this on the list (once my subscription is accepted). ---------------------------------------------------------------------- Comment By: Taco Hoekwater (taco) Date: 2006-01-12 10:22 Message: Logged In: YES user_id=1608 Like Hans, I also prefer separate if primitives, mainly because I do not want to have to remember the meanings of the possible integer values (for that reason, I'm not too happy about \currentgrouptype either). Taco ---------------------------------------------------------------------- Comment By: Nobody (None) Date: 2006-01-12 09:14 Message: Logged In: NO i wonder why we need \ifalignscanning or \stopalignscanner at all when eTeX already has this feature - any \protected macro stops the scanning. ---------------------------------------------------------------------- Comment By: Hans Hagen (hagen) Date: 2006-01-12 08:08 Message: Logged In: YES user_id=927 somehow i think that if's are a better idea than a register because in your case the register only registers one case at the same time (when i saw this patch the first time, i wondered why not a complete set was implemented) - ifincsname - ifinedef - ifinwrite - ifinspecial - ifinpdfliteral - ifinannotbody - ifinmessage (special case of write) - ifinalign - ifinmark probably some more (ok, normally all those conditions can comfortably be catched in a macro package but if we add them, we should be complete in addition to this there can be a register which keeps track of the innermost one (we can have ifcsname inside an edef inside an align concerning the \stopalignscanner i think it's better to have something primitive like \crcr, say \endalign because using if's can have its own problem (we should not worry to much about a name clash, since one can always let it to another one); so, we should wait with adding this patches till (1) we agree and (2) it is complete remark: also, it's dangerous to add patched before a decent decission/interface is dediced upon; once it's in, we cannot change it any more Hans ---------------------------------------------------------------------- You can respond by visiting: http://sarovar.org/tracker/?func=detail&atid=495&aid=469&group_id=106