Why the various definitions of the thin space ,?












3















Knuths definition of , is mskipthinmuskip.



LaTeX changes this definition to



DeclareRobustCommand{,}{%
relaxifmmodemskipthinmuskipelsethinspacefi
}
defthinspace{kern .16667em }


amsmath.sty says it's



DeclareRobustCommand{tmspace}[3]{%
ifmmodemskip#1#2elsekern#1#3firelax}
renewcommand{,}{tmspace+thinmuskip{.1667em}}


I might understand LaTeX's point to make a command usable also in text mode. But what's the point of the redefinition by amsmath?










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    3















    Knuths definition of , is mskipthinmuskip.



    LaTeX changes this definition to



    DeclareRobustCommand{,}{%
    relaxifmmodemskipthinmuskipelsethinspacefi
    }
    defthinspace{kern .16667em }


    amsmath.sty says it's



    DeclareRobustCommand{tmspace}[3]{%
    ifmmodemskip#1#2elsekern#1#3firelax}
    renewcommand{,}{tmspace+thinmuskip{.1667em}}


    I might understand LaTeX's point to make a command usable also in text mode. But what's the point of the redefinition by amsmath?










    share|improve this question



























      3












      3








      3


      1






      Knuths definition of , is mskipthinmuskip.



      LaTeX changes this definition to



      DeclareRobustCommand{,}{%
      relaxifmmodemskipthinmuskipelsethinspacefi
      }
      defthinspace{kern .16667em }


      amsmath.sty says it's



      DeclareRobustCommand{tmspace}[3]{%
      ifmmodemskip#1#2elsekern#1#3firelax}
      renewcommand{,}{tmspace+thinmuskip{.1667em}}


      I might understand LaTeX's point to make a command usable also in text mode. But what's the point of the redefinition by amsmath?










      share|improve this question
















      Knuths definition of , is mskipthinmuskip.



      LaTeX changes this definition to



      DeclareRobustCommand{,}{%
      relaxifmmodemskipthinmuskipelsethinspacefi
      }
      defthinspace{kern .16667em }


      amsmath.sty says it's



      DeclareRobustCommand{tmspace}[3]{%
      ifmmodemskip#1#2elsekern#1#3firelax}
      renewcommand{,}{tmspace+thinmuskip{.1667em}}


      I might understand LaTeX's point to make a command usable also in text mode. But what's the point of the redefinition by amsmath?







      spacing amsmath






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      edited 5 hours ago









      Sebastiano

      11.1k42164




      11.1k42164










      asked 5 hours ago









      user49915user49915

      617121




      617121






















          1 Answer
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          4














          You should look at the full picture:



           152   │ ifxleavevmode@ifvmode@undefined
          153 │ DeclareRobustCommand{tmspace}[3]{%
          154 │ ifmmodemskip#1#2elsekern#1#3firelax}
          155 │ else
          156 │ DeclareRobustCommand{tmspace}[3]{%
          157 │ ifmmodemskip#1#2elseleavevmode@ifvmodekern#1#3firelax}
          158 │ fi
          159 │ renewcommand{,}{tmspace+thinmuskip{.1667em}}
          160 │ letthinspace,
          161 │ renewcommand{!}{tmspace-thinmuskip{.1667em}}
          162 │ letnegthinspace!
          163 │ renewcommand{:}{tmspace+medmuskip{.2222em}}
          164 │ letmedspace:
          165 │ newcommand{negmedspace}{tmspace-medmuskip{.2222em}}
          166 │ renewcommand{;}{tmspace+thickmuskip{.2777em}}
          167 │ letthickspace;
          168 │ newcommand{negthickspace}{tmspace-thickmuskip{.2777em}}


          The two definitions of tmspace are due to recent decisions to make such commands start paragraph mode anyway. With a recent LaTeX kernel the second one will be used.



          Contrast this with the code in the LaTeX kernel:



          1619   │ DeclareRobustCommand{,}{%
          1620 │ relaxifmmodemskipthinmuskipelsethinspacefi
          1621 │ }

          1630 │ defthinspace{leavevmode@ifvmodekern .16667em }
          1631 │ defnegthinspace{leavevmode@ifvmodekern-.16667em }

          4543 │ def>{mskipmedmuskip}
          4544 │ def;{mskipthickmuskip}
          4545 │ def!{mskip-thinmuskip}

          4547 │ let:=>


          The approach of amsmath is much more rational and cleaner. They also provide text mode equivalent of all macros, whereas ! cannot be used in text mode if amsmath is not loaded, and similarly for the others. The final result will be essentially the same. However, a , command will be translated into tmspace+thinmuskip{.1667em} when written in an auxiliary file, instead of ,. Not really a big deal.






          share|improve this answer























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            4














            You should look at the full picture:



             152   │ ifxleavevmode@ifvmode@undefined
            153 │ DeclareRobustCommand{tmspace}[3]{%
            154 │ ifmmodemskip#1#2elsekern#1#3firelax}
            155 │ else
            156 │ DeclareRobustCommand{tmspace}[3]{%
            157 │ ifmmodemskip#1#2elseleavevmode@ifvmodekern#1#3firelax}
            158 │ fi
            159 │ renewcommand{,}{tmspace+thinmuskip{.1667em}}
            160 │ letthinspace,
            161 │ renewcommand{!}{tmspace-thinmuskip{.1667em}}
            162 │ letnegthinspace!
            163 │ renewcommand{:}{tmspace+medmuskip{.2222em}}
            164 │ letmedspace:
            165 │ newcommand{negmedspace}{tmspace-medmuskip{.2222em}}
            166 │ renewcommand{;}{tmspace+thickmuskip{.2777em}}
            167 │ letthickspace;
            168 │ newcommand{negthickspace}{tmspace-thickmuskip{.2777em}}


            The two definitions of tmspace are due to recent decisions to make such commands start paragraph mode anyway. With a recent LaTeX kernel the second one will be used.



            Contrast this with the code in the LaTeX kernel:



            1619   │ DeclareRobustCommand{,}{%
            1620 │ relaxifmmodemskipthinmuskipelsethinspacefi
            1621 │ }

            1630 │ defthinspace{leavevmode@ifvmodekern .16667em }
            1631 │ defnegthinspace{leavevmode@ifvmodekern-.16667em }

            4543 │ def>{mskipmedmuskip}
            4544 │ def;{mskipthickmuskip}
            4545 │ def!{mskip-thinmuskip}

            4547 │ let:=>


            The approach of amsmath is much more rational and cleaner. They also provide text mode equivalent of all macros, whereas ! cannot be used in text mode if amsmath is not loaded, and similarly for the others. The final result will be essentially the same. However, a , command will be translated into tmspace+thinmuskip{.1667em} when written in an auxiliary file, instead of ,. Not really a big deal.






            share|improve this answer




























              4














              You should look at the full picture:



               152   │ ifxleavevmode@ifvmode@undefined
              153 │ DeclareRobustCommand{tmspace}[3]{%
              154 │ ifmmodemskip#1#2elsekern#1#3firelax}
              155 │ else
              156 │ DeclareRobustCommand{tmspace}[3]{%
              157 │ ifmmodemskip#1#2elseleavevmode@ifvmodekern#1#3firelax}
              158 │ fi
              159 │ renewcommand{,}{tmspace+thinmuskip{.1667em}}
              160 │ letthinspace,
              161 │ renewcommand{!}{tmspace-thinmuskip{.1667em}}
              162 │ letnegthinspace!
              163 │ renewcommand{:}{tmspace+medmuskip{.2222em}}
              164 │ letmedspace:
              165 │ newcommand{negmedspace}{tmspace-medmuskip{.2222em}}
              166 │ renewcommand{;}{tmspace+thickmuskip{.2777em}}
              167 │ letthickspace;
              168 │ newcommand{negthickspace}{tmspace-thickmuskip{.2777em}}


              The two definitions of tmspace are due to recent decisions to make such commands start paragraph mode anyway. With a recent LaTeX kernel the second one will be used.



              Contrast this with the code in the LaTeX kernel:



              1619   │ DeclareRobustCommand{,}{%
              1620 │ relaxifmmodemskipthinmuskipelsethinspacefi
              1621 │ }

              1630 │ defthinspace{leavevmode@ifvmodekern .16667em }
              1631 │ defnegthinspace{leavevmode@ifvmodekern-.16667em }

              4543 │ def>{mskipmedmuskip}
              4544 │ def;{mskipthickmuskip}
              4545 │ def!{mskip-thinmuskip}

              4547 │ let:=>


              The approach of amsmath is much more rational and cleaner. They also provide text mode equivalent of all macros, whereas ! cannot be used in text mode if amsmath is not loaded, and similarly for the others. The final result will be essentially the same. However, a , command will be translated into tmspace+thinmuskip{.1667em} when written in an auxiliary file, instead of ,. Not really a big deal.






              share|improve this answer


























                4












                4








                4







                You should look at the full picture:



                 152   │ ifxleavevmode@ifvmode@undefined
                153 │ DeclareRobustCommand{tmspace}[3]{%
                154 │ ifmmodemskip#1#2elsekern#1#3firelax}
                155 │ else
                156 │ DeclareRobustCommand{tmspace}[3]{%
                157 │ ifmmodemskip#1#2elseleavevmode@ifvmodekern#1#3firelax}
                158 │ fi
                159 │ renewcommand{,}{tmspace+thinmuskip{.1667em}}
                160 │ letthinspace,
                161 │ renewcommand{!}{tmspace-thinmuskip{.1667em}}
                162 │ letnegthinspace!
                163 │ renewcommand{:}{tmspace+medmuskip{.2222em}}
                164 │ letmedspace:
                165 │ newcommand{negmedspace}{tmspace-medmuskip{.2222em}}
                166 │ renewcommand{;}{tmspace+thickmuskip{.2777em}}
                167 │ letthickspace;
                168 │ newcommand{negthickspace}{tmspace-thickmuskip{.2777em}}


                The two definitions of tmspace are due to recent decisions to make such commands start paragraph mode anyway. With a recent LaTeX kernel the second one will be used.



                Contrast this with the code in the LaTeX kernel:



                1619   │ DeclareRobustCommand{,}{%
                1620 │ relaxifmmodemskipthinmuskipelsethinspacefi
                1621 │ }

                1630 │ defthinspace{leavevmode@ifvmodekern .16667em }
                1631 │ defnegthinspace{leavevmode@ifvmodekern-.16667em }

                4543 │ def>{mskipmedmuskip}
                4544 │ def;{mskipthickmuskip}
                4545 │ def!{mskip-thinmuskip}

                4547 │ let:=>


                The approach of amsmath is much more rational and cleaner. They also provide text mode equivalent of all macros, whereas ! cannot be used in text mode if amsmath is not loaded, and similarly for the others. The final result will be essentially the same. However, a , command will be translated into tmspace+thinmuskip{.1667em} when written in an auxiliary file, instead of ,. Not really a big deal.






                share|improve this answer













                You should look at the full picture:



                 152   │ ifxleavevmode@ifvmode@undefined
                153 │ DeclareRobustCommand{tmspace}[3]{%
                154 │ ifmmodemskip#1#2elsekern#1#3firelax}
                155 │ else
                156 │ DeclareRobustCommand{tmspace}[3]{%
                157 │ ifmmodemskip#1#2elseleavevmode@ifvmodekern#1#3firelax}
                158 │ fi
                159 │ renewcommand{,}{tmspace+thinmuskip{.1667em}}
                160 │ letthinspace,
                161 │ renewcommand{!}{tmspace-thinmuskip{.1667em}}
                162 │ letnegthinspace!
                163 │ renewcommand{:}{tmspace+medmuskip{.2222em}}
                164 │ letmedspace:
                165 │ newcommand{negmedspace}{tmspace-medmuskip{.2222em}}
                166 │ renewcommand{;}{tmspace+thickmuskip{.2777em}}
                167 │ letthickspace;
                168 │ newcommand{negthickspace}{tmspace-thickmuskip{.2777em}}


                The two definitions of tmspace are due to recent decisions to make such commands start paragraph mode anyway. With a recent LaTeX kernel the second one will be used.



                Contrast this with the code in the LaTeX kernel:



                1619   │ DeclareRobustCommand{,}{%
                1620 │ relaxifmmodemskipthinmuskipelsethinspacefi
                1621 │ }

                1630 │ defthinspace{leavevmode@ifvmodekern .16667em }
                1631 │ defnegthinspace{leavevmode@ifvmodekern-.16667em }

                4543 │ def>{mskipmedmuskip}
                4544 │ def;{mskipthickmuskip}
                4545 │ def!{mskip-thinmuskip}

                4547 │ let:=>


                The approach of amsmath is much more rational and cleaner. They also provide text mode equivalent of all macros, whereas ! cannot be used in text mode if amsmath is not loaded, and similarly for the others. The final result will be essentially the same. However, a , command will be translated into tmspace+thinmuskip{.1667em} when written in an auxiliary file, instead of ,. Not really a big deal.







                share|improve this answer












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                answered 5 hours ago









                egregegreg

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