Eppure a me accade. Ti posto il file .log:
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This is pdfTeXk, Version 3.141592-1.40.3 (Web2C 7.5.6) (format=latex 2010.11.16) 23 JUN 2011 12:27
entering extended mode
%&-line parsing enabled.
**xy.tex
(./xy.tex
LaTeX2e <2005/12/01>
Babel
yphenation, arabic, basque, bulgarian, coptic, welsh, czech, slovak, german, ng
erman, danish, esperanto, spanish, catalan, galician, estonian, farsi, finnish,
french, greek, monogreek, ancientgreek, croatian, hungarian, interlingua, ibyc
us, indonesian, icelandic, italian, latin, mongolian, dutch, norsk, polish, por
tuguese, pinyin, romanian, russian, slovenian, uppersorbian, serbian, swedish,
turkish, ukenglish, ukrainian, loaded.
(/usr/local/texlive/2007/texmf-dist/tex/latex/base/article.cls
Document Class: article 2005/09/16 v1.4f Standard LaTeX document class
(/usr/local/texlive/2007/texmf-dist/tex/latex/base/size10.clo
File: size10.clo 2005/09/16 v1.4f Standard LaTeX file (size option)
)
\c@part=\count79
\c@section=\count80
\c@subsection=\count81
\c@subsubsection=\count82
\c@paragraph=\count83
\c@subparagraph=\count84
\c@figure=\count85
\c@table=\count86
\abovecaptionskip=\skip41
\belowcaptionskip=\skip42
\bibindent=\dimen102
)
(/usr/local/texlive/2007/texmf-dist/tex/generic/xypic/xy.sty (./xy.tex
! LaTeX Error: Two \documentclass or \documentstyle commands.
See the LaTeX manual or LaTeX Companion for explanation.
Type H
…
l.1 \documentclass{
article}
?
(./xy.aux)
\openout1 = `xy.aux'.
LaTeX Font Info: Checking defaults for OML/cmm/m/it on input line 5.
LaTeX Font Info: … okay on input line 5.
LaTeX Font Info: Checking defaults for T1/cmr/m/n on input line 5.
LaTeX Font Info: … okay on input line 5.
LaTeX Font Info: Checking defaults for OT1/cmr/m/n on input line 5.
LaTeX Font Info: … okay on input line 5.
LaTeX Font Info: Checking defaults for OMS/cmsy/m/n on input line 5.
LaTeX Font Info: … okay on input line 5.
LaTeX Font Info: Checking defaults for OMX/cmex/m/n on input line 5.
LaTeX Font Info: … okay on input line 5.
LaTeX Font Info: Checking defaults for U/cmr/m/n on input line 5.
LaTeX Font Info: … okay on input line 5.
! Undefined control sequence.
l.15 \xymatrix
?
! Misplaced alignment tab character &.
l.16 A &
B \\
?
! Misplaced alignment tab character &.
l.17 C &
D
?
! Too many }'s.
l.19 }
?
[1
] (./xy.aux) ) ) )
Here is how much of TeX's memory you used:
211 strings out of 94074
2354 string characters out of 1163015
48804 words of memory out of 1500000
3577 multiletter control sequences out of 10000+50000
3640 words of font info for 14 fonts, out of 1200000 for 2000
645 hyphenation exceptions out of 8191
23i,4n,17p,138b,107s stack positions out of 5000i,500n,6000p,200000b,5000s
Output written on xy.dvi (1 page, 236 bytes).
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Ciao,
davide