Change the catcode and then define a (Unicode) character

Clash Royale CLAN TAG#URR8PPP

up vote
3
down vote

favorite

The motivation is that I sometimes have, e.g.

% !TEX encoding = UTF-8 Unicode
catcode`¯=active
def¯#1#2overline#1#2
$¯ab+¯bc=¯ac$

in my code.
I thought it would be nice if there is a macro, say activatedefine,
such that

activatedefine¯#1#2overline#1#2

does the job that catcode and def do.

I understand that it is not correct to write

defactivatedefine#1
 catcode`#1=active
 def#1

because the catcode of the #1 in the third line is not changed.
But then I hear that futurelet can duplicate tokens.
So I came up with

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defnowwecanplaywiththechar
 expandaftercatcodeexpandafter`thechar=13
 def

This is still not quite right because thechar does not expand to ¯.
So I try to fix it

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defgobbletwo#1 #2 
defnowwecanplaywiththechar
 edefactivatethechar
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 %message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 %message^^J The catcode becomes thecatcode`¯^^J^^J
 def

activatedefine¯#1#2overline#1#2

This macro does change the catcode of ¯ to 13.
But TeX complains Missing control sequence inserted.

What is going wrong with my code?

Edit

Almost forgot MWE

% !TEX TS-program = XeLaTeX
% !TEX encoding = UTF-8 Unicode

documentclassarticle
begindocument

defactivatedefinefutureletthecharnowwecanplaywiththechar
%defnowwecanplaywiththechar
% expandaftercatcodeexpandafter`thechar=13
% def
%

defgobbletwo#1 #2 
defnowwecanplaywiththechar%
 edefactivatethechar%
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 message^^J The catcode becomes thecatcode`¯^^J^^J
 def¯

activatedefine¯#1#2overline#1#2

enddocument

xetex luatex catcodes

share|improve this question

edited 15 mins ago

asked 41 mins ago

Symbol 1

24k235111

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using futurelet will freeze the catcode of the next token (the one to which the macro is let). This may or not be relevant to your problems (I admit not having read in detail).
  – jfbu
  37 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It's not a good idea to make the back quote active.
  – egreg
  30 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  also what do you mean by Uniocde here? if you are using pdftex you can only define single byte tokens this way not arbitrary unicode characters.
  – David Carlisle
  27 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu That futurelet will freeze the catcode is unexpected (by me). That answers why TeX complains.
  – Symbol 1
  25 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @egreg I did not want to make back quote active. If my code did that it is unintended. I (only) want to make non-ASCII characters active.
  – Symbol 1
  23 mins ago
  

  
  
  
  

 | 
show 4 more comments

up vote
3
down vote

favorite

The motivation is that I sometimes have, e.g.

% !TEX encoding = UTF-8 Unicode
catcode`¯=active
def¯#1#2overline#1#2
$¯ab+¯bc=¯ac$

in my code.
I thought it would be nice if there is a macro, say activatedefine,
such that

activatedefine¯#1#2overline#1#2

does the job that catcode and def do.

I understand that it is not correct to write

defactivatedefine#1
 catcode`#1=active
 def#1

because the catcode of the #1 in the third line is not changed.
But then I hear that futurelet can duplicate tokens.
So I came up with

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defnowwecanplaywiththechar
 expandaftercatcodeexpandafter`thechar=13
 def

This is still not quite right because thechar does not expand to ¯.
So I try to fix it

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defgobbletwo#1 #2 
defnowwecanplaywiththechar
 edefactivatethechar
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 %message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 %message^^J The catcode becomes thecatcode`¯^^J^^J
 def

activatedefine¯#1#2overline#1#2

This macro does change the catcode of ¯ to 13.
But TeX complains Missing control sequence inserted.

What is going wrong with my code?

Edit

Almost forgot MWE

% !TEX TS-program = XeLaTeX
% !TEX encoding = UTF-8 Unicode

documentclassarticle
begindocument

defactivatedefinefutureletthecharnowwecanplaywiththechar
%defnowwecanplaywiththechar
% expandaftercatcodeexpandafter`thechar=13
% def
%

defgobbletwo#1 #2 
defnowwecanplaywiththechar%
 edefactivatethechar%
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 message^^J The catcode becomes thecatcode`¯^^J^^J
 def¯

activatedefine¯#1#2overline#1#2

enddocument

xetex luatex catcodes

share|improve this question

edited 15 mins ago

asked 41 mins ago

Symbol 1

24k235111

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using futurelet will freeze the catcode of the next token (the one to which the macro is let). This may or not be relevant to your problems (I admit not having read in detail).
  – jfbu
  37 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It's not a good idea to make the back quote active.
  – egreg
  30 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  also what do you mean by Uniocde here? if you are using pdftex you can only define single byte tokens this way not arbitrary unicode characters.
  – David Carlisle
  27 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu That futurelet will freeze the catcode is unexpected (by me). That answers why TeX complains.
  – Symbol 1
  25 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @egreg I did not want to make back quote active. If my code did that it is unintended. I (only) want to make non-ASCII characters active.
  – Symbol 1
  23 mins ago
  

  
  
  
  

 | 
show 4 more comments

up vote
3
down vote

favorite

up vote
3
down vote

favorite

The motivation is that I sometimes have, e.g.

% !TEX encoding = UTF-8 Unicode
catcode`¯=active
def¯#1#2overline#1#2
$¯ab+¯bc=¯ac$

in my code.
I thought it would be nice if there is a macro, say activatedefine,
such that

activatedefine¯#1#2overline#1#2

does the job that catcode and def do.

I understand that it is not correct to write

defactivatedefine#1
 catcode`#1=active
 def#1

because the catcode of the #1 in the third line is not changed.
But then I hear that futurelet can duplicate tokens.
So I came up with

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defnowwecanplaywiththechar
 expandaftercatcodeexpandafter`thechar=13
 def

This is still not quite right because thechar does not expand to ¯.
So I try to fix it

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defgobbletwo#1 #2 
defnowwecanplaywiththechar
 edefactivatethechar
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 %message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 %message^^J The catcode becomes thecatcode`¯^^J^^J
 def

activatedefine¯#1#2overline#1#2

This macro does change the catcode of ¯ to 13.
But TeX complains Missing control sequence inserted.

What is going wrong with my code?

Edit

Almost forgot MWE

% !TEX TS-program = XeLaTeX
% !TEX encoding = UTF-8 Unicode

documentclassarticle
begindocument

defactivatedefinefutureletthecharnowwecanplaywiththechar
%defnowwecanplaywiththechar
% expandaftercatcodeexpandafter`thechar=13
% def
%

defgobbletwo#1 #2 
defnowwecanplaywiththechar%
 edefactivatethechar%
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 message^^J The catcode becomes thecatcode`¯^^J^^J
 def¯

activatedefine¯#1#2overline#1#2

enddocument

xetex luatex catcodes

share|improve this question

edited 15 mins ago

asked 41 mins ago

Symbol 1

24k235111

The motivation is that I sometimes have, e.g.

% !TEX encoding = UTF-8 Unicode
catcode`¯=active
def¯#1#2overline#1#2
$¯ab+¯bc=¯ac$

in my code.
I thought it would be nice if there is a macro, say activatedefine,
such that

activatedefine¯#1#2overline#1#2

does the job that catcode and def do.

I understand that it is not correct to write

defactivatedefine#1
 catcode`#1=active
 def#1

because the catcode of the #1 in the third line is not changed.
But then I hear that futurelet can duplicate tokens.
So I came up with

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defnowwecanplaywiththechar
 expandaftercatcodeexpandafter`thechar=13
 def

This is still not quite right because thechar does not expand to ¯.
So I try to fix it

defactivatedefine
 futureletthecharnowwecanplaywiththechar

defgobbletwo#1 #2 
defnowwecanplaywiththechar
 edefactivatethechar
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 %message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 %message^^J The catcode becomes thecatcode`¯^^J^^J
 def

activatedefine¯#1#2overline#1#2

This macro does change the catcode of ¯ to 13.
But TeX complains Missing control sequence inserted.

What is going wrong with my code?

Edit

Almost forgot MWE

% !TEX TS-program = XeLaTeX
% !TEX encoding = UTF-8 Unicode

documentclassarticle
begindocument

defactivatedefinefutureletthecharnowwecanplaywiththechar
%defnowwecanplaywiththechar
% expandaftercatcodeexpandafter`thechar=13
% def
%

defgobbletwo#1 #2 
defnowwecanplaywiththechar%
 edefactivatethechar%
 noexpandcatcode`expandaftergobbletwomeaningthechar=active
 
 message^^J^^J stringactivatethechar is meaningactivatethechar
 activatethechar
 message^^J The catcode becomes thecatcode`¯^^J^^J
 def¯

activatedefine¯#1#2overline#1#2

enddocument

xetex luatex catcodes

xetex luatex catcodes

share|improve this question

edited 15 mins ago

asked 41 mins ago

Symbol 1

24k235111

share|improve this question

edited 15 mins ago

asked 41 mins ago

Symbol 1

24k235111

share|improve this question

share|improve this question

edited 15 mins ago

edited 15 mins ago

edited 15 mins ago

asked 41 mins ago

Symbol 1

24k235111

asked 41 mins ago

Symbol 1

24k235111

asked 41 mins ago

Symbol 1

24k235111

24k235111

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using futurelet will freeze the catcode of the next token (the one to which the macro is let). This may or not be relevant to your problems (I admit not having read in detail).
  – jfbu
  37 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It's not a good idea to make the back quote active.
  – egreg
  30 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  also what do you mean by Uniocde here? if you are using pdftex you can only define single byte tokens this way not arbitrary unicode characters.
  – David Carlisle
  27 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu That futurelet will freeze the catcode is unexpected (by me). That answers why TeX complains.
  – Symbol 1
  25 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @egreg I did not want to make back quote active. If my code did that it is unintended. I (only) want to make non-ASCII characters active.
  – Symbol 1
  23 mins ago
  

  
  
  
  

 | 
show 4 more comments

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using futurelet will freeze the catcode of the next token (the one to which the macro is let). This may or not be relevant to your problems (I admit not having read in detail).
  – jfbu
  37 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It's not a good idea to make the back quote active.
  – egreg
  30 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  also what do you mean by Uniocde here? if you are using pdftex you can only define single byte tokens this way not arbitrary unicode characters.
  – David Carlisle
  27 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu That futurelet will freeze the catcode is unexpected (by me). That answers why TeX complains.
  – Symbol 1
  25 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @egreg I did not want to make back quote active. If my code did that it is unintended. I (only) want to make non-ASCII characters active.
  – Symbol 1
  23 mins ago
  

  
  
  
  

using futurelet will freeze the catcode of the next token (the one to which the macro is let). This may or not be relevant to your problems (I admit not having read in detail).
– jfbu
37 mins ago

using futurelet will freeze the catcode of the next token (the one to which the macro is let). This may or not be relevant to your problems (I admit not having read in detail).
– jfbu
37 mins ago

It's not a good idea to make the back quote active.
– egreg
30 mins ago

It's not a good idea to make the back quote active.
– egreg
30 mins ago

also what do you mean by Uniocde here? if you are using pdftex you can only define single byte tokens this way not arbitrary unicode characters.
– David Carlisle
27 mins ago

also what do you mean by Uniocde here? if you are using pdftex you can only define single byte tokens this way not arbitrary unicode characters.
– David Carlisle
27 mins ago

@jfbu That futurelet will freeze the catcode is unexpected (by me). That answers why TeX complains.
– Symbol 1
25 mins ago

@jfbu That futurelet will freeze the catcode is unexpected (by me). That answers why TeX complains.
– Symbol 1
25 mins ago

@egreg I did not want to make back quote active. If my code did that it is unintended. I (only) want to make non-ASCII characters active.
– Symbol 1
23 mins ago

@egreg I did not want to make back quote active. If my code did that it is unintended. I (only) want to make non-ASCII characters active.
– Symbol 1
23 mins ago

 | 
show 4 more comments

2 Answers
2

active

oldest

votes

up vote
4
down vote



accepted

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupdef~%

activatedefine¯#1#2overline#1#2

begindocument

$¯ab+¯bc=¯ac$
enddocument

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine|#1#2overline#1#2

begindocument
$|ab+|bc=|ac$
enddocument

I did not pay much attention to the actual macro, which is in math mode so math active would be possibly better.

Besides I don't want to have to handle UTF-8, so I used | rather for the example.

---

AH! but OP is using XeTeX. So we can do this

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine¯#1#2overline#1#2

begindocument
thecatcode`¯ % ONLY XETEX, NOT PDFTEX!

$¯ab+¯bc=¯ac$
enddocument
% Local variables:
% TeX-engine: xetex
% End:

Problem with pdflatex is that ¯ is multibyte, and the erased code at top of my answer was redefinig the first byte, breaking LaTeX UTF-8.

share|improve this answer

edited 17 mins ago

answered 34 mins ago

jfbu

41.8k61134

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Yes sorry don't take any notice of me
  – David Carlisle
  24 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Your trick works in XeLaTeX. Are you suggesting that lowercase will reevaluate the catcode of ¯?
  – Symbol 1
  16 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  The tilde is active. The lowercase modifies the character code, but keeps the category code. So it creates an active token, which we can define. Then we must not forget to actually make this character associated to active category code.
  – jfbu
  13 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Where can I find the exact behavior of lowercase, including what you just said? Why on earth can lowercase contains assignments... This blows my mind.
  – Symbol 1
  3 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  TeX by Topic 3.6.4 Creative use of uppercase and lowercase. A bit terse... but search this site for egreg+lowercase for many many examples.
  – jfbu
  2 mins ago
  
  

  
  
  
  

add a comment | 

up vote
2
down vote

The simplest way is to use newunicodechar; it just defines parameterless macros, but we can exploit the fact TeX is a macro expansion language to begin with.

Note that these examples can be used with all TeX engines (except Knuth TeX).

documentclassarticle

usepackagenewunicodechar

newunicodechar‾overline

newcommandtwooverline[2]overline#1#2
newunicodechar﹌twooverline

begindocument

$‾a$ $﹌ab$

enddocument

Another example:

documentclassarticle

usepackagenewunicodechar

makeatletter
newunicodechar‾symbol@overline
defsymbol@overline#1‾overline#1 % must go second

begindocument

$‾abc‾$

enddocument

share|improve this answer

edited 2 mins ago

answered 14 mins ago

egreg

682k8318133061

add a comment | 

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
4
down vote



accepted

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupdef~%

activatedefine¯#1#2overline#1#2

begindocument

$¯ab+¯bc=¯ac$
enddocument

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine|#1#2overline#1#2

begindocument
$|ab+|bc=|ac$
enddocument

I did not pay much attention to the actual macro, which is in math mode so math active would be possibly better.

Besides I don't want to have to handle UTF-8, so I used | rather for the example.

---

AH! but OP is using XeTeX. So we can do this

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine¯#1#2overline#1#2

begindocument
thecatcode`¯ % ONLY XETEX, NOT PDFTEX!

$¯ab+¯bc=¯ac$
enddocument
% Local variables:
% TeX-engine: xetex
% End:

Problem with pdflatex is that ¯ is multibyte, and the erased code at top of my answer was redefinig the first byte, breaking LaTeX UTF-8.

share|improve this answer

edited 17 mins ago

answered 34 mins ago

jfbu

41.8k61134

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Yes sorry don't take any notice of me
  – David Carlisle
  24 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Your trick works in XeLaTeX. Are you suggesting that lowercase will reevaluate the catcode of ¯?
  – Symbol 1
  16 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  The tilde is active. The lowercase modifies the character code, but keeps the category code. So it creates an active token, which we can define. Then we must not forget to actually make this character associated to active category code.
  – jfbu
  13 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Where can I find the exact behavior of lowercase, including what you just said? Why on earth can lowercase contains assignments... This blows my mind.
  – Symbol 1
  3 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  TeX by Topic 3.6.4 Creative use of uppercase and lowercase. A bit terse... but search this site for egreg+lowercase for many many examples.
  – jfbu
  2 mins ago
  
  

  
  
  
  

add a comment | 

up vote
4
down vote



accepted

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupdef~%

activatedefine¯#1#2overline#1#2

begindocument

$¯ab+¯bc=¯ac$
enddocument

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine|#1#2overline#1#2

begindocument
$|ab+|bc=|ac$
enddocument

I did not pay much attention to the actual macro, which is in math mode so math active would be possibly better.

Besides I don't want to have to handle UTF-8, so I used | rather for the example.

---

AH! but OP is using XeTeX. So we can do this

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine¯#1#2overline#1#2

begindocument
thecatcode`¯ % ONLY XETEX, NOT PDFTEX!

$¯ab+¯bc=¯ac$
enddocument
% Local variables:
% TeX-engine: xetex
% End:

Problem with pdflatex is that ¯ is multibyte, and the erased code at top of my answer was redefinig the first byte, breaking LaTeX UTF-8.

share|improve this answer

edited 17 mins ago

answered 34 mins ago

jfbu

41.8k61134

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Yes sorry don't take any notice of me
  – David Carlisle
  24 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Your trick works in XeLaTeX. Are you suggesting that lowercase will reevaluate the catcode of ¯?
  – Symbol 1
  16 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  The tilde is active. The lowercase modifies the character code, but keeps the category code. So it creates an active token, which we can define. Then we must not forget to actually make this character associated to active category code.
  – jfbu
  13 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Where can I find the exact behavior of lowercase, including what you just said? Why on earth can lowercase contains assignments... This blows my mind.
  – Symbol 1
  3 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  TeX by Topic 3.6.4 Creative use of uppercase and lowercase. A bit terse... but search this site for egreg+lowercase for many many examples.
  – jfbu
  2 mins ago
  
  

  
  
  
  

add a comment | 

up vote
4
down vote



accepted

up vote
4
down vote



accepted

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupdef~%

activatedefine¯#1#2overline#1#2

begindocument

$¯ab+¯bc=¯ac$
enddocument

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine|#1#2overline#1#2

begindocument
$|ab+|bc=|ac$
enddocument

I did not pay much attention to the actual macro, which is in math mode so math active would be possibly better.

Besides I don't want to have to handle UTF-8, so I used | rather for the example.

---

AH! but OP is using XeTeX. So we can do this

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine¯#1#2overline#1#2

begindocument
thecatcode`¯ % ONLY XETEX, NOT PDFTEX!

$¯ab+¯bc=¯ac$
enddocument
% Local variables:
% TeX-engine: xetex
% End:

Problem with pdflatex is that ¯ is multibyte, and the erased code at top of my answer was redefinig the first byte, breaking LaTeX UTF-8.

share|improve this answer

edited 17 mins ago

answered 34 mins ago

jfbu

41.8k61134

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupdef~%

activatedefine¯#1#2overline#1#2

begindocument

$¯ab+¯bc=¯ac$
enddocument

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine|#1#2overline#1#2

begindocument
$|ab+|bc=|ac$
enddocument

I did not pay much attention to the actual macro, which is in math mode so math active would be possibly better.

Besides I don't want to have to handle UTF-8, so I used | rather for the example.

---

AH! but OP is using XeTeX. So we can do this

documentclassarticle

defactivatedefine#1begingrouplccode`~=`#1relax
 lowercaseendgroupcatcode`#1activedef~%

activatedefine¯#1#2overline#1#2

begindocument
thecatcode`¯ % ONLY XETEX, NOT PDFTEX!

$¯ab+¯bc=¯ac$
enddocument
% Local variables:
% TeX-engine: xetex
% End:

Problem with pdflatex is that ¯ is multibyte, and the erased code at top of my answer was redefinig the first byte, breaking LaTeX UTF-8.

share|improve this answer

edited 17 mins ago

answered 34 mins ago

jfbu

41.8k61134

share|improve this answer

share|improve this answer

edited 17 mins ago

edited 17 mins ago

edited 17 mins ago

answered 34 mins ago

jfbu

41.8k61134

answered 34 mins ago

jfbu

41.8k61134

answered 34 mins ago

jfbu

41.8k61134

41.8k61134

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Yes sorry don't take any notice of me
  – David Carlisle
  24 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Your trick works in XeLaTeX. Are you suggesting that lowercase will reevaluate the catcode of ¯?
  – Symbol 1
  16 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  The tilde is active. The lowercase modifies the character code, but keeps the category code. So it creates an active token, which we can define. Then we must not forget to actually make this character associated to active category code.
  – jfbu
  13 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Where can I find the exact behavior of lowercase, including what you just said? Why on earth can lowercase contains assignments... This blows my mind.
  – Symbol 1
  3 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  TeX by Topic 3.6.4 Creative use of uppercase and lowercase. A bit terse... but search this site for egreg+lowercase for many many examples.
  – jfbu
  2 mins ago
  
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Yes sorry don't take any notice of me
  – David Carlisle
  24 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Your trick works in XeLaTeX. Are you suggesting that lowercase will reevaluate the catcode of ¯?
  – Symbol 1
  16 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  The tilde is active. The lowercase modifies the character code, but keeps the category code. So it creates an active token, which we can define. Then we must not forget to actually make this character associated to active category code.
  – jfbu
  13 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @jfbu Where can I find the exact behavior of lowercase, including what you just said? Why on earth can lowercase contains assignments... This blows my mind.
  – Symbol 1
  3 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  TeX by Topic 3.6.4 Creative use of uppercase and lowercase. A bit terse... but search this site for egreg+lowercase for many many examples.
  – jfbu
  2 mins ago
  
  

  
  
  
  

Yes sorry don't take any notice of me
– David Carlisle
24 mins ago

Yes sorry don't take any notice of me
– David Carlisle
24 mins ago

@jfbu Your trick works in XeLaTeX. Are you suggesting that lowercase will reevaluate the catcode of ¯?
– Symbol 1
16 mins ago

@jfbu Your trick works in XeLaTeX. Are you suggesting that lowercase will reevaluate the catcode of ¯?
– Symbol 1
16 mins ago

The tilde is active. The lowercase modifies the character code, but keeps the category code. So it creates an active token, which we can define. Then we must not forget to actually make this character associated to active category code.
– jfbu
13 mins ago

The tilde is active. The lowercase modifies the character code, but keeps the category code. So it creates an active token, which we can define. Then we must not forget to actually make this character associated to active category code.
– jfbu
13 mins ago

@jfbu Where can I find the exact behavior of lowercase, including what you just said? Why on earth can lowercase contains assignments... This blows my mind.
– Symbol 1
3 mins ago

@jfbu Where can I find the exact behavior of lowercase, including what you just said? Why on earth can lowercase contains assignments... This blows my mind.
– Symbol 1
3 mins ago

TeX by Topic 3.6.4 Creative use of uppercase and lowercase. A bit terse... but search this site for egreg+lowercase for many many examples.
– jfbu
2 mins ago

TeX by Topic 3.6.4 Creative use of uppercase and lowercase. A bit terse... but search this site for egreg+lowercase for many many examples.
– jfbu
2 mins ago

add a comment | 

up vote
2
down vote

The simplest way is to use newunicodechar; it just defines parameterless macros, but we can exploit the fact TeX is a macro expansion language to begin with.

Note that these examples can be used with all TeX engines (except Knuth TeX).

documentclassarticle

usepackagenewunicodechar

newunicodechar‾overline

newcommandtwooverline[2]overline#1#2
newunicodechar﹌twooverline

begindocument

$‾a$ $﹌ab$

enddocument

Another example:

documentclassarticle

usepackagenewunicodechar

makeatletter
newunicodechar‾symbol@overline
defsymbol@overline#1‾overline#1 % must go second

begindocument

$‾abc‾$

enddocument

share|improve this answer

edited 2 mins ago

answered 14 mins ago

egreg

682k8318133061

add a comment | 

up vote
2
down vote

The simplest way is to use newunicodechar; it just defines parameterless macros, but we can exploit the fact TeX is a macro expansion language to begin with.

Note that these examples can be used with all TeX engines (except Knuth TeX).

documentclassarticle

usepackagenewunicodechar

newunicodechar‾overline

newcommandtwooverline[2]overline#1#2
newunicodechar﹌twooverline

begindocument

$‾a$ $﹌ab$

enddocument

Another example:

documentclassarticle

usepackagenewunicodechar

makeatletter
newunicodechar‾symbol@overline
defsymbol@overline#1‾overline#1 % must go second

begindocument

$‾abc‾$

enddocument

share|improve this answer

edited 2 mins ago

answered 14 mins ago

egreg

682k8318133061

add a comment | 

up vote
2
down vote

up vote
2
down vote

The simplest way is to use newunicodechar; it just defines parameterless macros, but we can exploit the fact TeX is a macro expansion language to begin with.

Note that these examples can be used with all TeX engines (except Knuth TeX).

documentclassarticle

usepackagenewunicodechar

newunicodechar‾overline

newcommandtwooverline[2]overline#1#2
newunicodechar﹌twooverline

begindocument

$‾a$ $﹌ab$

enddocument

Another example:

documentclassarticle

usepackagenewunicodechar

makeatletter
newunicodechar‾symbol@overline
defsymbol@overline#1‾overline#1 % must go second

begindocument

$‾abc‾$

enddocument

share|improve this answer

edited 2 mins ago

answered 14 mins ago

egreg

682k8318133061

The simplest way is to use newunicodechar; it just defines parameterless macros, but we can exploit the fact TeX is a macro expansion language to begin with.

Note that these examples can be used with all TeX engines (except Knuth TeX).

documentclassarticle

usepackagenewunicodechar

newunicodechar‾overline

newcommandtwooverline[2]overline#1#2
newunicodechar﹌twooverline

begindocument

$‾a$ $﹌ab$

enddocument

Another example:

documentclassarticle

usepackagenewunicodechar

makeatletter
newunicodechar‾symbol@overline
defsymbol@overline#1‾overline#1 % must go second

begindocument

$‾abc‾$

enddocument

share|improve this answer

edited 2 mins ago

answered 14 mins ago

egreg

682k8318133061

share|improve this answer

share|improve this answer

edited 2 mins ago

edited 2 mins ago

edited 2 mins ago

answered 14 mins ago

egreg

682k8318133061

answered 14 mins ago

egreg

682k8318133061

answered 14 mins ago

egreg

682k8318133061

682k8318133061

add a comment | 

add a comment | 

 

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