Use of noexpand in the implementation of TextOrMath for eTeX
In latexrelease 2015/01/01, there are two implementations of TextOrMath: one for regular
TeX, the other one for eTeX-like engines (more precisely: those which support protected). My question concerns the latter:
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
(...) } % no problem here
edefTextOrMath#1#2{% from latex.ltx
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
I think I understand well these definitions, however I can't figure out why the edef isn't simply written this way:
edefTextOrMath#1#2{% from me
csname TextOrMathspaceendcsname
{#1}{#2}}
Since the internal TextOrMath<space> macro is protected, what is the point of preceding it with noexpand inside the edef? Is it because the author feared that protected might be deficient?..
I made a test like this (ran with pdfTeX):
% From latex.ltx (or p. 153 of source2e.pdf)
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
ifmmode expandafter@secondoftwo
else expandafter@firstoftwo fi}
edefTextOrMath#1#2{%
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
% My simpler way of doing the same (?)
edefaltTextOrMath#1#2{%
csname TextOrMathspaceendcsname
{#1}{#2}}
showTextOrMath % TextOrMath=macro:#1#2->TextOrMath {#1}{#2}.
showaltTextOrMath % altTextOrMath=ditto
ifxTextOrMathaltTextOrMath
identical
else
different
fi
vfill
eject
bye
This test prints 'identical' and seems to indicate that my definition is equivalent to the one in latex.ltx (but slightly simpler). Did I miss something?
Thanks!
macros expansion definition protected-macro
asked Apr 2 at 18:56
frougonfrougon
756611
add a comment |
In latexrelease 2015/01/01, there are two implementations of TextOrMath: one for regular
TeX, the other one for eTeX-like engines (more precisely: those which support protected). My question concerns the latter:
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
(...) } % no problem here
edefTextOrMath#1#2{% from latex.ltx
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
I think I understand well these definitions, however I can't figure out why the edef isn't simply written this way:
edefTextOrMath#1#2{% from me
csname TextOrMathspaceendcsname
{#1}{#2}}
Since the internal TextOrMath<space> macro is protected, what is the point of preceding it with noexpand inside the edef? Is it because the author feared that protected might be deficient?..
I made a test like this (ran with pdfTeX):
% From latex.ltx (or p. 153 of source2e.pdf)
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
ifmmode expandafter@secondoftwo
else expandafter@firstoftwo fi}
edefTextOrMath#1#2{%
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
% My simpler way of doing the same (?)
edefaltTextOrMath#1#2{%
csname TextOrMathspaceendcsname
{#1}{#2}}
showTextOrMath % TextOrMath=macro:#1#2->TextOrMath {#1}{#2}.
showaltTextOrMath % altTextOrMath=ditto
ifxTextOrMathaltTextOrMath
identical
else
different
fi
vfill
eject
bye
This test prints 'identical' and seems to indicate that my definition is equivalent to the one in latex.ltx (but slightly simpler). Did I miss something?
Thanks!
macros expansion definition protected-macro
asked Apr 2 at 18:56
frougonfrougon
756611
thanks I suppose we could change that:-)
– David Carlisle
Apr 2 at 20:24
Many thanks for your insight into this, I was really puzzled!
– frougon
Apr 2 at 20:26
add a comment |
In latexrelease 2015/01/01, there are two implementations of TextOrMath: one for regular
TeX, the other one for eTeX-like engines (more precisely: those which support protected). My question concerns the latter:
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
(...) } % no problem here
edefTextOrMath#1#2{% from latex.ltx
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
I think I understand well these definitions, however I can't figure out why the edef isn't simply written this way:
edefTextOrMath#1#2{% from me
csname TextOrMathspaceendcsname
{#1}{#2}}
Since the internal TextOrMath<space> macro is protected, what is the point of preceding it with noexpand inside the edef? Is it because the author feared that protected might be deficient?..
I made a test like this (ran with pdfTeX):
% From latex.ltx (or p. 153 of source2e.pdf)
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
ifmmode expandafter@secondoftwo
else expandafter@firstoftwo fi}
edefTextOrMath#1#2{%
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
% My simpler way of doing the same (?)
edefaltTextOrMath#1#2{%
csname TextOrMathspaceendcsname
{#1}{#2}}
showTextOrMath % TextOrMath=macro:#1#2->TextOrMath {#1}{#2}.
showaltTextOrMath % altTextOrMath=ditto
ifxTextOrMathaltTextOrMath
identical
else
different
fi
vfill
eject
bye
This test prints 'identical' and seems to indicate that my definition is equivalent to the one in latex.ltx (but slightly simpler). Did I miss something?
Thanks!
macros expansion definition protected-macro
asked Apr 2 at 18:56
frougonfrougon
756611
In latexrelease 2015/01/01, there are two implementations of TextOrMath: one for regular
TeX, the other one for eTeX-like engines (more precisely: those which support protected). My question concerns the latter:
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
(...) } % no problem here
edefTextOrMath#1#2{% from latex.ltx
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
I think I understand well these definitions, however I can't figure out why the edef isn't simply written this way:
edefTextOrMath#1#2{% from me
csname TextOrMathspaceendcsname
{#1}{#2}}
Since the internal TextOrMath<space> macro is protected, what is the point of preceding it with noexpand inside the edef? Is it because the author feared that protected might be deficient?..
I made a test like this (ran with pdfTeX):
% From latex.ltx (or p. 153 of source2e.pdf)
protectedexpandafterdefcsname TextOrMathspaceendcsname{%
ifmmode expandafter@secondoftwo
else expandafter@firstoftwo fi}
edefTextOrMath#1#2{%
expandafternoexpandcsname TextOrMathspaceendcsname
{#1}{#2}}
% My simpler way of doing the same (?)
edefaltTextOrMath#1#2{%
csname TextOrMathspaceendcsname
{#1}{#2}}
showTextOrMath % TextOrMath=macro:#1#2->TextOrMath {#1}{#2}.
showaltTextOrMath % altTextOrMath=ditto
ifxTextOrMathaltTextOrMath
identical
else
different
fi
vfill
eject
bye
This test prints 'identical' and seems to indicate that my definition is equivalent to the one in latex.ltx (but slightly simpler). Did I miss something?
Thanks!
macros expansion definition protected-macro
macros expansion definition protected-macro
asked Apr 2 at 18:56
frougonfrougon
756611
asked Apr 2 at 18:56
frougonfrougon
756611
asked Apr 2 at 18:56
frougonfrougon
756611
asked Apr 2 at 18:56
frougonfrougon
756611
asked Apr 2 at 18:56
frougonfrougon
756611
756611
thanks I suppose we could change that:-)
– David Carlisle
Apr 2 at 20:24
Many thanks for your insight into this, I was really puzzled!
– frougon
Apr 2 at 20:26
add a comment |
thanks I suppose we could change that:-)
– David Carlisle
Apr 2 at 20:24
Many thanks for your insight into this, I was really puzzled!
– frougon
Apr 2 at 20:26
thanks I suppose we could change that:-)
– David Carlisle
Apr 2 at 20:24
thanks I suppose we could change that:-)
– David Carlisle
Apr 2 at 20:24
Many thanks for your insight into this, I was really puzzled!
– frougon
Apr 2 at 20:26
Many thanks for your insight into this, I was really puzzled!
– frougon
Apr 2 at 20:26
add a comment |
1 Answer
1
active
oldest
votes
No you didn't miss anything, just old habits die hard as we gradually add these modern post 1992 features into the sources....
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
add a comment |
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1 Answer
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1 Answer
1
active
oldest
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active
oldest
votes
No you didn't miss anything, just old habits die hard as we gradually add these modern post 1992 features into the sources....
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
add a comment |
No you didn't miss anything, just old habits die hard as we gradually add these modern post 1992 features into the sources....
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
add a comment |
No you didn't miss anything, just old habits die hard as we gradually add these modern post 1992 features into the sources....
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
No you didn't miss anything, just old habits die hard as we gradually add these modern post 1992 features into the sources....
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
answered Apr 2 at 20:14
David CarlisleDavid Carlisle
497k4111441892
497k4111441892
add a comment |
add a comment |
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thanks I suppose we could change that:-)
– David Carlisle
Apr 2 at 20:24
Many thanks for your insight into this, I was really puzzled!
– frougon
Apr 2 at 20:26