How can LaTeX read utf8?












6















As described in the TeXbook, TeX reads files byte by byte, regardless of the particular format -- as I understand, this is just how INITEX is set up.



I also understand that LaTeX is just a collection of macros built on top of INITEX, described in most distributions of TeX by the file 'latex.ltx'.



The above two things are at odds with my understanding of LaTeX's ability to read utf8. I was under the impression that reading the input byte by byte (and thus for instance, only being able to access numbers from 0 to 255 using char or something) was baked into TeX, and thus would exist in all variants built on top of it.



Thus, how is LaTeX able to do this?






unicode







share|improve this question


















  • 4





    The TeXbook describes the so-called Knuth-TeX engine, as well as a collection of macros frequently called "PlainTeX". Are you aware of newer engines called pdfTeX, XeTeX, and LuaTeX?

    – Mico
    8 hours ago






  • 2





    You could be asking one of (at least) two questions here. Are you wondering how e.g. XeTeX (natively UTF-8) can be derived from Knuth's TeX (8-bit). Or are you wondering how 8-bit TeX engines deal with UTF-8 input (conversion of 'raw' bytes to codpoints to output)?

    – Joseph Wright♦
    2 hours ago
















6















As described in the TeXbook, TeX reads files byte by byte, regardless of the particular format -- as I understand, this is just how INITEX is set up.



I also understand that LaTeX is just a collection of macros built on top of INITEX, described in most distributions of TeX by the file 'latex.ltx'.



The above two things are at odds with my understanding of LaTeX's ability to read utf8. I was under the impression that reading the input byte by byte (and thus for instance, only being able to access numbers from 0 to 255 using char or something) was baked into TeX, and thus would exist in all variants built on top of it.



Thus, how is LaTeX able to do this?






unicode







share|improve this question


















  • 4





    The TeXbook describes the so-called Knuth-TeX engine, as well as a collection of macros frequently called "PlainTeX". Are you aware of newer engines called pdfTeX, XeTeX, and LuaTeX?

    – Mico
    8 hours ago






  • 2





    You could be asking one of (at least) two questions here. Are you wondering how e.g. XeTeX (natively UTF-8) can be derived from Knuth's TeX (8-bit). Or are you wondering how 8-bit TeX engines deal with UTF-8 input (conversion of 'raw' bytes to codpoints to output)?

    – Joseph Wright♦
    2 hours ago














6












6








6


1






As described in the TeXbook, TeX reads files byte by byte, regardless of the particular format -- as I understand, this is just how INITEX is set up.



I also understand that LaTeX is just a collection of macros built on top of INITEX, described in most distributions of TeX by the file 'latex.ltx'.



The above two things are at odds with my understanding of LaTeX's ability to read utf8. I was under the impression that reading the input byte by byte (and thus for instance, only being able to access numbers from 0 to 255 using char or something) was baked into TeX, and thus would exist in all variants built on top of it.



Thus, how is LaTeX able to do this?






unicode







share|improve this question














As described in the TeXbook, TeX reads files byte by byte, regardless of the particular format -- as I understand, this is just how INITEX is set up.



I also understand that LaTeX is just a collection of macros built on top of INITEX, described in most distributions of TeX by the file 'latex.ltx'.



The above two things are at odds with my understanding of LaTeX's ability to read utf8. I was under the impression that reading the input byte by byte (and thus for instance, only being able to access numbers from 0 to 255 using char or something) was baked into TeX, and thus would exist in all variants built on top of it.



Thus, how is LaTeX able to do this?






unicode




unicode






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked 8 hours ago









extremeaxe5extremeaxe5

2444




2444








  • 4





    The TeXbook describes the so-called Knuth-TeX engine, as well as a collection of macros frequently called "PlainTeX". Are you aware of newer engines called pdfTeX, XeTeX, and LuaTeX?

    – Mico
    8 hours ago






  • 2





    You could be asking one of (at least) two questions here. Are you wondering how e.g. XeTeX (natively UTF-8) can be derived from Knuth's TeX (8-bit). Or are you wondering how 8-bit TeX engines deal with UTF-8 input (conversion of 'raw' bytes to codpoints to output)?

    – Joseph Wright♦
    2 hours ago














  • 4





    The TeXbook describes the so-called Knuth-TeX engine, as well as a collection of macros frequently called "PlainTeX". Are you aware of newer engines called pdfTeX, XeTeX, and LuaTeX?

    – Mico
    8 hours ago






  • 2





    You could be asking one of (at least) two questions here. Are you wondering how e.g. XeTeX (natively UTF-8) can be derived from Knuth's TeX (8-bit). Or are you wondering how 8-bit TeX engines deal with UTF-8 input (conversion of 'raw' bytes to codpoints to output)?

    – Joseph Wright♦
    2 hours ago








4




4





The TeXbook describes the so-called Knuth-TeX engine, as well as a collection of macros frequently called "PlainTeX". Are you aware of newer engines called pdfTeX, XeTeX, and LuaTeX?

– Mico
8 hours ago





The TeXbook describes the so-called Knuth-TeX engine, as well as a collection of macros frequently called "PlainTeX". Are you aware of newer engines called pdfTeX, XeTeX, and LuaTeX?

– Mico
8 hours ago




2




2





You could be asking one of (at least) two questions here. Are you wondering how e.g. XeTeX (natively UTF-8) can be derived from Knuth's TeX (8-bit). Or are you wondering how 8-bit TeX engines deal with UTF-8 input (conversion of 'raw' bytes to codpoints to output)?

– Joseph Wright♦
2 hours ago





You could be asking one of (at least) two questions here. Are you wondering how e.g. XeTeX (natively UTF-8) can be derived from Knuth's TeX (8-bit). Or are you wondering how 8-bit TeX engines deal with UTF-8 input (conversion of 'raw' bytes to codpoints to output)?

– Joseph Wright♦
2 hours ago










1 Answer
1






active

oldest

votes


















8














If you want to know how the 8-bit engines handle utf8 input you can use tracingmacros:



documentclass{article}



begin{document}

{tracingmacros =1 ä }

end{document}


which gives



Ã->UTFviii@two@octets Ã



UTFviii@two@octets #1#2->expandafter UTFviii@defined csname u8:#1string #2

endcsname 

#1<-Ã

#2<-¤



UTFviii@defined #1->ifx #1relax if relax expandafter UTFviii@checkseq s

tring #1relax relax UTFviii@undefined@err {#1}else PackageError {inputenc}

{Invalid UTF-8 byte sequence}UTFviii@invalid@help fi else expandafter #1fi



#1<-u8:ä 



u8:ä ->IeC {"a}


That means the the first byte of the ä (the Ã) is an active char, a command which then picks up the next byte and then calls u8:ä which calls "a. In this way (pdf)latex can handle quite a lot of utf8 input but it has e.g. problems with "char + combining accent" as there is no sensible code for the combining accent to go back to add an accent on the char.






share|improve this answer
























  • Just a comment to point out log file containing the trace got viewed by editor in some 8bit encoding, presumably iso-latin-1 (like Emacs does for me), not in UTF8... so à is only one byte. This is tacit in your answer...

    – jfbu
    1 hour ago













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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









8














If you want to know how the 8-bit engines handle utf8 input you can use tracingmacros:



documentclass{article}



begin{document}

{tracingmacros =1 ä }

end{document}


which gives



Ã->UTFviii@two@octets Ã



UTFviii@two@octets #1#2->expandafter UTFviii@defined csname u8:#1string #2

endcsname 

#1<-Ã

#2<-¤



UTFviii@defined #1->ifx #1relax if relax expandafter UTFviii@checkseq s

tring #1relax relax UTFviii@undefined@err {#1}else PackageError {inputenc}

{Invalid UTF-8 byte sequence}UTFviii@invalid@help fi else expandafter #1fi



#1<-u8:ä 



u8:ä ->IeC {"a}


That means the the first byte of the ä (the Ã) is an active char, a command which then picks up the next byte and then calls u8:ä which calls "a. In this way (pdf)latex can handle quite a lot of utf8 input but it has e.g. problems with "char + combining accent" as there is no sensible code for the combining accent to go back to add an accent on the char.






share|improve this answer
























  • Just a comment to point out log file containing the trace got viewed by editor in some 8bit encoding, presumably iso-latin-1 (like Emacs does for me), not in UTF8... so à is only one byte. This is tacit in your answer...

    – jfbu
    1 hour ago


















8














If you want to know how the 8-bit engines handle utf8 input you can use tracingmacros:



documentclass{article}



begin{document}

{tracingmacros =1 ä }

end{document}


which gives



Ã->UTFviii@two@octets Ã



UTFviii@two@octets #1#2->expandafter UTFviii@defined csname u8:#1string #2

endcsname 

#1<-Ã

#2<-¤



UTFviii@defined #1->ifx #1relax if relax expandafter UTFviii@checkseq s

tring #1relax relax UTFviii@undefined@err {#1}else PackageError {inputenc}

{Invalid UTF-8 byte sequence}UTFviii@invalid@help fi else expandafter #1fi



#1<-u8:ä 



u8:ä ->IeC {"a}


That means the the first byte of the ä (the Ã) is an active char, a command which then picks up the next byte and then calls u8:ä which calls "a. In this way (pdf)latex can handle quite a lot of utf8 input but it has e.g. problems with "char + combining accent" as there is no sensible code for the combining accent to go back to add an accent on the char.






share|improve this answer
























  • Just a comment to point out log file containing the trace got viewed by editor in some 8bit encoding, presumably iso-latin-1 (like Emacs does for me), not in UTF8... so à is only one byte. This is tacit in your answer...

    – jfbu
    1 hour ago
















8












8








8







If you want to know how the 8-bit engines handle utf8 input you can use tracingmacros:



documentclass{article}



begin{document}

{tracingmacros =1 ä }

end{document}


which gives



Ã->UTFviii@two@octets Ã



UTFviii@two@octets #1#2->expandafter UTFviii@defined csname u8:#1string #2

endcsname 

#1<-Ã

#2<-¤



UTFviii@defined #1->ifx #1relax if relax expandafter UTFviii@checkseq s

tring #1relax relax UTFviii@undefined@err {#1}else PackageError {inputenc}

{Invalid UTF-8 byte sequence}UTFviii@invalid@help fi else expandafter #1fi



#1<-u8:ä 



u8:ä ->IeC {"a}


That means the the first byte of the ä (the Ã) is an active char, a command which then picks up the next byte and then calls u8:ä which calls "a. In this way (pdf)latex can handle quite a lot of utf8 input but it has e.g. problems with "char + combining accent" as there is no sensible code for the combining accent to go back to add an accent on the char.






share|improve this answer













If you want to know how the 8-bit engines handle utf8 input you can use tracingmacros:



documentclass{article}



begin{document}

{tracingmacros =1 ä }

end{document}


which gives



Ã->UTFviii@two@octets Ã



UTFviii@two@octets #1#2->expandafter UTFviii@defined csname u8:#1string #2

endcsname 

#1<-Ã

#2<-¤



UTFviii@defined #1->ifx #1relax if relax expandafter UTFviii@checkseq s

tring #1relax relax UTFviii@undefined@err {#1}else PackageError {inputenc}

{Invalid UTF-8 byte sequence}UTFviii@invalid@help fi else expandafter #1fi



#1<-u8:ä 



u8:ä ->IeC {"a}


That means the the first byte of the ä (the Ã) is an active char, a command which then picks up the next byte and then calls u8:ä which calls "a. In this way (pdf)latex can handle quite a lot of utf8 input but it has e.g. problems with "char + combining accent" as there is no sensible code for the combining accent to go back to add an accent on the char.







share|improve this answer












share|improve this answer



share|improve this answer










answered 1 hour ago









Ulrike FischerUlrike Fischer

189k7295676




189k7295676













  • Just a comment to point out log file containing the trace got viewed by editor in some 8bit encoding, presumably iso-latin-1 (like Emacs does for me), not in UTF8... so à is only one byte. This is tacit in your answer...

    – jfbu
    1 hour ago





















  • Just a comment to point out log file containing the trace got viewed by editor in some 8bit encoding, presumably iso-latin-1 (like Emacs does for me), not in UTF8... so à is only one byte. This is tacit in your answer...

    – jfbu
    1 hour ago



















Just a comment to point out log file containing the trace got viewed by editor in some 8bit encoding, presumably iso-latin-1 (like Emacs does for me), not in UTF8... so à is only one byte. This is tacit in your answer...

– jfbu
1 hour ago







Just a comment to point out log file containing the trace got viewed by editor in some 8bit encoding, presumably iso-latin-1 (like Emacs does for me), not in UTF8... so à is only one byte. This is tacit in your answer...

– jfbu
1 hour ago




















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