brister@decwrl.dec.com (James Brister) (01/31/91)
Could someone clue me in why line 1 doesn't work, but line 2 does.
1) \uppercase{\romannumeral\count0}
2) \uppercase\expandafter{\romannumeral\count0}
Why, in the first example, doesn't the '\romannumeral\count0' get expanded
to the token string, before \uppercase sees it.
I think this is due the 'stomach' vs. 'mouth' business of TeX (a concept
I'm not too clear on yet). True?
Thanks
James
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James Brister brister@decwrl.dec.com
DEC Western Software Lab., Palo Alto, CA {uunet,sun,pyramid}!decwrl!bristereijkhout@s41.csrd.uiuc.edu (Victor Eijkhout) (01/31/91)
brister@decwrl.dec.com (James Brister) writes: >Could someone clue me in why line 1 doesn't work, but line 2 does. > 1) \uppercase{\romannumeral\count0} > 2) \uppercase\expandafter{\romannumeral\count0} It is the definition of \uppercase that it takes a token list and uppercases every character token in it. You wouldn't want the reverse, because then things like \def\IsUppercaseChar#1{\uppercase{\if#1}#1} wouldn't work because the \if is expandable. The second line works because \uppercase has to expand in order to find its opening brace: that can be implicit. This in contrast to \def\foo\expandafter{\romannumeral 4} which is *not* the same as \def\foo{iv} Victor.
jcb@cs.ed.ac.uk (Julian Bradfield) (02/01/91)
In article <BRISTER.91Jan30170400@saratoga.decwrl.dec.com> brister@decwrl.dec.com (James Brister) writes: > 1) \uppercase{\romannumeral\count0} > 2) \uppercase\expandafter{\romannumeral\count0} >Why, in the first example, doesn't the '\romannumeral\count0' get expanded >to the token string, before \uppercase sees it. >I think this is due the 'stomach' vs. 'mouth' business of TeX (a concept >I'm not too clear on yet). True? No, it's all happening in the mouth. In line 1, \uppercase wants a token list, and expansion is switched off when reading this list (it's one of the cases listed in Chap. 20). In line 2, the \expandafter forces expansion of \romannumeral ; the expansion is put back after the {, and then the token list for \uppercase is read as normal, without expansion. (Expansion is switched off when TeX sees the left brace starting the token list.)