Euler and minus sign












8















I'm trying to define a macro to typeset Eulers complex e-power with or without a minus sign in its argument. I would like the macro to automatically detect if its argument starts with a -. I have the following MWE which uses and optional argument:



documentclass[a4paper,12pt,fleqn]{article}

defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
defimunit{mathrm{imaginaryunit}} % ... in upright math
defce{mathrm{e}} % the constant e, upright of course
makeatletter
defepowim{@ifnextchar[{epowimi}{epowimi}} % e to-the-power-of imaginary unit
defepowimi[#1]#2{ce^{#1ifimaginaryunit jrelax,fiimunit#2}} % e to-the-power-of imaginary unit
makeatother

begin{document}

begin{equation}
epowim{alpha}qquad epowim[-]{alpha} qquad ce^{-imunitalpha}
end{equation}

end{document}


So I would like a macro that detects if its argument starts with a -:



epowim{-alpha}


should detect the - and place it before the imaginary unit instead of placing it after the imaginary unit.



So the question is if it can be done and how.










share|improve this question





























    8















    I'm trying to define a macro to typeset Eulers complex e-power with or without a minus sign in its argument. I would like the macro to automatically detect if its argument starts with a -. I have the following MWE which uses and optional argument:



    documentclass[a4paper,12pt,fleqn]{article}

    defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
    defimunit{mathrm{imaginaryunit}} % ... in upright math
    defce{mathrm{e}} % the constant e, upright of course
    makeatletter
    defepowim{@ifnextchar[{epowimi}{epowimi}} % e to-the-power-of imaginary unit
    defepowimi[#1]#2{ce^{#1ifimaginaryunit jrelax,fiimunit#2}} % e to-the-power-of imaginary unit
    makeatother

    begin{document}

    begin{equation}
    epowim{alpha}qquad epowim[-]{alpha} qquad ce^{-imunitalpha}
    end{equation}

    end{document}


    So I would like a macro that detects if its argument starts with a -:



    epowim{-alpha}


    should detect the - and place it before the imaginary unit instead of placing it after the imaginary unit.



    So the question is if it can be done and how.










    share|improve this question



























      8












      8








      8


      0






      I'm trying to define a macro to typeset Eulers complex e-power with or without a minus sign in its argument. I would like the macro to automatically detect if its argument starts with a -. I have the following MWE which uses and optional argument:



      documentclass[a4paper,12pt,fleqn]{article}

      defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
      defimunit{mathrm{imaginaryunit}} % ... in upright math
      defce{mathrm{e}} % the constant e, upright of course
      makeatletter
      defepowim{@ifnextchar[{epowimi}{epowimi}} % e to-the-power-of imaginary unit
      defepowimi[#1]#2{ce^{#1ifimaginaryunit jrelax,fiimunit#2}} % e to-the-power-of imaginary unit
      makeatother

      begin{document}

      begin{equation}
      epowim{alpha}qquad epowim[-]{alpha} qquad ce^{-imunitalpha}
      end{equation}

      end{document}


      So I would like a macro that detects if its argument starts with a -:



      epowim{-alpha}


      should detect the - and place it before the imaginary unit instead of placing it after the imaginary unit.



      So the question is if it can be done and how.










      share|improve this question
















      I'm trying to define a macro to typeset Eulers complex e-power with or without a minus sign in its argument. I would like the macro to automatically detect if its argument starts with a -. I have the following MWE which uses and optional argument:



      documentclass[a4paper,12pt,fleqn]{article}

      defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
      defimunit{mathrm{imaginaryunit}} % ... in upright math
      defce{mathrm{e}} % the constant e, upright of course
      makeatletter
      defepowim{@ifnextchar[{epowimi}{epowimi}} % e to-the-power-of imaginary unit
      defepowimi[#1]#2{ce^{#1ifimaginaryunit jrelax,fiimunit#2}} % e to-the-power-of imaginary unit
      makeatother

      begin{document}

      begin{equation}
      epowim{alpha}qquad epowim[-]{alpha} qquad ce^{-imunitalpha}
      end{equation}

      end{document}


      So I would like a macro that detects if its argument starts with a -:



      epowim{-alpha}


      should detect the - and place it before the imaginary unit instead of placing it after the imaginary unit.



      So the question is if it can be done and how.







      math-mode optional-arguments






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 6 hours ago







      Jesse op den Brouw

















      asked 6 hours ago









      Jesse op den BrouwJesse op den Brouw

      537119




      537119






















          2 Answers
          2






          active

          oldest

          votes


















          7














          Something like this?



          documentclass[a4paper,12pt,fleqn]{article}
          defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
          defimunit{mathrm{imaginaryunit}} % ... in upright math
          defce{mathrm{e}} % the constant e, upright of course
          newcommandepowim[1]{ce^{epowimaux#1relaxendep}}
          defepowimaux#1#2endep{ifx-#1relax-imunitelse%
          if jimaginaryunitrelax,fiimunit#1fi#2}
          begin{document}
          [
          epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
          ]
          [
          epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
          ]
          defimaginaryunit{i}
          [
          epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
          ]
          [
          epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
          ]
          end{document}


          enter image description here






          share|improve this answer





















          • 1





            Exactly what i need. I changed the definition to defepowimaux#1#2endep{ifx-#1relax-imunitelseifimaginaryunit jrelax,fiimunit#1fi#2} to compensate for the fact that the j is too close to the e but not when using i as imaginary unit

            – Jesse op den Brouw
            6 hours ago













          • @JesseopdenBrouw Thanks. And feel free to adapt to your need.

            – Steven B. Segletes
            6 hours ago











          • @JesseopdenBrouw I might only suggest using if jimaginaryunit rather than ifimaginaryunit j. Or better still, expandafterifximaginaryunit j

            – Steven B. Segletes
            6 hours ago











          • I see nothing wrong in ifimaginaryunit j, provided imaginaryunit is either i or j. Oh, and did you try epowim{-}? ;-)

            – egreg
            3 hours ago











          • @egreg I detect no problems with epowim{-}. As to the if test, you are right if the choices are always i or j. But users have a tendency to do strange stuff, like something that expands to i or j, or a different letter or symbol altogether, etc. I was trying to head off crazy stuff.

            – Steven B. Segletes
            2 hours ago



















          3














          Avoid def, your life will be easier.



          Since you seem to know about @ifnextchar:



          documentclass[a4paper,12pt,fleqn]{article}

          % the imaginary unit, j for engineers and i for the rest of the world
          newcommandimaginaryunit{j}
          % in upright type as engineers do; also Euler's constant
          newcommandimunit{mathrm{imaginaryunit}}
          newcommandce{mathrm{e}}

          newcommand{fiximunit}{ifimaginaryunit j,fi}

          makeatletter
          newcommand{epowim}[1]{ce^{epowim@#1}}
          newcommand{epowim@}{@ifnextchar-{epowim@@}{epowim@@{fiximunit}}}
          newcommand{epowim@@}[1]{#1imunit}
          makeatother

          begin{document}

          begin{equation}
          epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
          qquad epowim{} qquad epowim{-}
          end{equation}

          end{document}


          Explanation: @ifnextchar- uses the next argument if - is found, the successive one otherwise, but without removing -. So if - is called the result will be



          epowim@@-alpha


          which passes - as argument to epowim@@. Otherwise epowim@@ is called with fiximunit as argument.



          This would not fail with epowim{} or epowim{-} to typeset ej and e−j respectively.



          A perhaps simpler implementation with xparse:



          documentclass[a4paper,12pt,fleqn]{article}

          usepackage{xparse}

          % the imaginary unit, j for engineers and i for the rest of the world
          newcommandimaginaryunit{j}
          % in upright type as engineers do; also Euler's constant
          newcommandimunit{mathrm{imaginaryunit}}
          newcommandce{mathrm{e}}

          newcommand{fiximunit}{ifimaginaryunit j,fi}

          NewDocumentCommand{epowim}{m}{ce^{powim#1}}
          NewDocumentCommand{powim}{t-}{IfBooleanTF{#1}{-imunit}{fiximunitimunit}}

          begin{document}

          begin{equation}
          epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
          qquad epowim{} qquad epowim{-}
          end{equation}

          end{document}


          enter image description here






          share|improve this answer

























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            2 Answers
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            active

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            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            7














            Something like this?



            documentclass[a4paper,12pt,fleqn]{article}
            defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
            defimunit{mathrm{imaginaryunit}} % ... in upright math
            defce{mathrm{e}} % the constant e, upright of course
            newcommandepowim[1]{ce^{epowimaux#1relaxendep}}
            defepowimaux#1#2endep{ifx-#1relax-imunitelse%
            if jimaginaryunitrelax,fiimunit#1fi#2}
            begin{document}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            defimaginaryunit{i}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            end{document}


            enter image description here






            share|improve this answer





















            • 1





              Exactly what i need. I changed the definition to defepowimaux#1#2endep{ifx-#1relax-imunitelseifimaginaryunit jrelax,fiimunit#1fi#2} to compensate for the fact that the j is too close to the e but not when using i as imaginary unit

              – Jesse op den Brouw
              6 hours ago













            • @JesseopdenBrouw Thanks. And feel free to adapt to your need.

              – Steven B. Segletes
              6 hours ago











            • @JesseopdenBrouw I might only suggest using if jimaginaryunit rather than ifimaginaryunit j. Or better still, expandafterifximaginaryunit j

              – Steven B. Segletes
              6 hours ago











            • I see nothing wrong in ifimaginaryunit j, provided imaginaryunit is either i or j. Oh, and did you try epowim{-}? ;-)

              – egreg
              3 hours ago











            • @egreg I detect no problems with epowim{-}. As to the if test, you are right if the choices are always i or j. But users have a tendency to do strange stuff, like something that expands to i or j, or a different letter or symbol altogether, etc. I was trying to head off crazy stuff.

              – Steven B. Segletes
              2 hours ago
















            7














            Something like this?



            documentclass[a4paper,12pt,fleqn]{article}
            defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
            defimunit{mathrm{imaginaryunit}} % ... in upright math
            defce{mathrm{e}} % the constant e, upright of course
            newcommandepowim[1]{ce^{epowimaux#1relaxendep}}
            defepowimaux#1#2endep{ifx-#1relax-imunitelse%
            if jimaginaryunitrelax,fiimunit#1fi#2}
            begin{document}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            defimaginaryunit{i}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            end{document}


            enter image description here






            share|improve this answer





















            • 1





              Exactly what i need. I changed the definition to defepowimaux#1#2endep{ifx-#1relax-imunitelseifimaginaryunit jrelax,fiimunit#1fi#2} to compensate for the fact that the j is too close to the e but not when using i as imaginary unit

              – Jesse op den Brouw
              6 hours ago













            • @JesseopdenBrouw Thanks. And feel free to adapt to your need.

              – Steven B. Segletes
              6 hours ago











            • @JesseopdenBrouw I might only suggest using if jimaginaryunit rather than ifimaginaryunit j. Or better still, expandafterifximaginaryunit j

              – Steven B. Segletes
              6 hours ago











            • I see nothing wrong in ifimaginaryunit j, provided imaginaryunit is either i or j. Oh, and did you try epowim{-}? ;-)

              – egreg
              3 hours ago











            • @egreg I detect no problems with epowim{-}. As to the if test, you are right if the choices are always i or j. But users have a tendency to do strange stuff, like something that expands to i or j, or a different letter or symbol altogether, etc. I was trying to head off crazy stuff.

              – Steven B. Segletes
              2 hours ago














            7












            7








            7







            Something like this?



            documentclass[a4paper,12pt,fleqn]{article}
            defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
            defimunit{mathrm{imaginaryunit}} % ... in upright math
            defce{mathrm{e}} % the constant e, upright of course
            newcommandepowim[1]{ce^{epowimaux#1relaxendep}}
            defepowimaux#1#2endep{ifx-#1relax-imunitelse%
            if jimaginaryunitrelax,fiimunit#1fi#2}
            begin{document}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            defimaginaryunit{i}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            end{document}


            enter image description here






            share|improve this answer















            Something like this?



            documentclass[a4paper,12pt,fleqn]{article}
            defimaginaryunit{j} % the imaginary unit, i for mathematician and theoretical physicist, j for the rest of the world.
            defimunit{mathrm{imaginaryunit}} % ... in upright math
            defce{mathrm{e}} % the constant e, upright of course
            newcommandepowim[1]{ce^{epowimaux#1relaxendep}}
            defepowimaux#1#2endep{ifx-#1relax-imunitelse%
            if jimaginaryunitrelax,fiimunit#1fi#2}
            begin{document}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            defimaginaryunit{i}
            [
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            ]
            [
            epowim{x+t}quadepowim{-x+t}quadepowim{-}quadepowim{}
            ]
            end{document}


            enter image description here







            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 1 hour ago

























            answered 6 hours ago









            Steven B. SegletesSteven B. Segletes

            156k9201411




            156k9201411








            • 1





              Exactly what i need. I changed the definition to defepowimaux#1#2endep{ifx-#1relax-imunitelseifimaginaryunit jrelax,fiimunit#1fi#2} to compensate for the fact that the j is too close to the e but not when using i as imaginary unit

              – Jesse op den Brouw
              6 hours ago













            • @JesseopdenBrouw Thanks. And feel free to adapt to your need.

              – Steven B. Segletes
              6 hours ago











            • @JesseopdenBrouw I might only suggest using if jimaginaryunit rather than ifimaginaryunit j. Or better still, expandafterifximaginaryunit j

              – Steven B. Segletes
              6 hours ago











            • I see nothing wrong in ifimaginaryunit j, provided imaginaryunit is either i or j. Oh, and did you try epowim{-}? ;-)

              – egreg
              3 hours ago











            • @egreg I detect no problems with epowim{-}. As to the if test, you are right if the choices are always i or j. But users have a tendency to do strange stuff, like something that expands to i or j, or a different letter or symbol altogether, etc. I was trying to head off crazy stuff.

              – Steven B. Segletes
              2 hours ago














            • 1





              Exactly what i need. I changed the definition to defepowimaux#1#2endep{ifx-#1relax-imunitelseifimaginaryunit jrelax,fiimunit#1fi#2} to compensate for the fact that the j is too close to the e but not when using i as imaginary unit

              – Jesse op den Brouw
              6 hours ago













            • @JesseopdenBrouw Thanks. And feel free to adapt to your need.

              – Steven B. Segletes
              6 hours ago











            • @JesseopdenBrouw I might only suggest using if jimaginaryunit rather than ifimaginaryunit j. Or better still, expandafterifximaginaryunit j

              – Steven B. Segletes
              6 hours ago











            • I see nothing wrong in ifimaginaryunit j, provided imaginaryunit is either i or j. Oh, and did you try epowim{-}? ;-)

              – egreg
              3 hours ago











            • @egreg I detect no problems with epowim{-}. As to the if test, you are right if the choices are always i or j. But users have a tendency to do strange stuff, like something that expands to i or j, or a different letter or symbol altogether, etc. I was trying to head off crazy stuff.

              – Steven B. Segletes
              2 hours ago








            1




            1





            Exactly what i need. I changed the definition to defepowimaux#1#2endep{ifx-#1relax-imunitelseifimaginaryunit jrelax,fiimunit#1fi#2} to compensate for the fact that the j is too close to the e but not when using i as imaginary unit

            – Jesse op den Brouw
            6 hours ago







            Exactly what i need. I changed the definition to defepowimaux#1#2endep{ifx-#1relax-imunitelseifimaginaryunit jrelax,fiimunit#1fi#2} to compensate for the fact that the j is too close to the e but not when using i as imaginary unit

            – Jesse op den Brouw
            6 hours ago















            @JesseopdenBrouw Thanks. And feel free to adapt to your need.

            – Steven B. Segletes
            6 hours ago





            @JesseopdenBrouw Thanks. And feel free to adapt to your need.

            – Steven B. Segletes
            6 hours ago













            @JesseopdenBrouw I might only suggest using if jimaginaryunit rather than ifimaginaryunit j. Or better still, expandafterifximaginaryunit j

            – Steven B. Segletes
            6 hours ago





            @JesseopdenBrouw I might only suggest using if jimaginaryunit rather than ifimaginaryunit j. Or better still, expandafterifximaginaryunit j

            – Steven B. Segletes
            6 hours ago













            I see nothing wrong in ifimaginaryunit j, provided imaginaryunit is either i or j. Oh, and did you try epowim{-}? ;-)

            – egreg
            3 hours ago





            I see nothing wrong in ifimaginaryunit j, provided imaginaryunit is either i or j. Oh, and did you try epowim{-}? ;-)

            – egreg
            3 hours ago













            @egreg I detect no problems with epowim{-}. As to the if test, you are right if the choices are always i or j. But users have a tendency to do strange stuff, like something that expands to i or j, or a different letter or symbol altogether, etc. I was trying to head off crazy stuff.

            – Steven B. Segletes
            2 hours ago





            @egreg I detect no problems with epowim{-}. As to the if test, you are right if the choices are always i or j. But users have a tendency to do strange stuff, like something that expands to i or j, or a different letter or symbol altogether, etc. I was trying to head off crazy stuff.

            – Steven B. Segletes
            2 hours ago











            3














            Avoid def, your life will be easier.



            Since you seem to know about @ifnextchar:



            documentclass[a4paper,12pt,fleqn]{article}

            % the imaginary unit, j for engineers and i for the rest of the world
            newcommandimaginaryunit{j}
            % in upright type as engineers do; also Euler's constant
            newcommandimunit{mathrm{imaginaryunit}}
            newcommandce{mathrm{e}}

            newcommand{fiximunit}{ifimaginaryunit j,fi}

            makeatletter
            newcommand{epowim}[1]{ce^{epowim@#1}}
            newcommand{epowim@}{@ifnextchar-{epowim@@}{epowim@@{fiximunit}}}
            newcommand{epowim@@}[1]{#1imunit}
            makeatother

            begin{document}

            begin{equation}
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            qquad epowim{} qquad epowim{-}
            end{equation}

            end{document}


            Explanation: @ifnextchar- uses the next argument if - is found, the successive one otherwise, but without removing -. So if - is called the result will be



            epowim@@-alpha


            which passes - as argument to epowim@@. Otherwise epowim@@ is called with fiximunit as argument.



            This would not fail with epowim{} or epowim{-} to typeset ej and e−j respectively.



            A perhaps simpler implementation with xparse:



            documentclass[a4paper,12pt,fleqn]{article}

            usepackage{xparse}

            % the imaginary unit, j for engineers and i for the rest of the world
            newcommandimaginaryunit{j}
            % in upright type as engineers do; also Euler's constant
            newcommandimunit{mathrm{imaginaryunit}}
            newcommandce{mathrm{e}}

            newcommand{fiximunit}{ifimaginaryunit j,fi}

            NewDocumentCommand{epowim}{m}{ce^{powim#1}}
            NewDocumentCommand{powim}{t-}{IfBooleanTF{#1}{-imunit}{fiximunitimunit}}

            begin{document}

            begin{equation}
            epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
            qquad epowim{} qquad epowim{-}
            end{equation}

            end{document}


            enter image description here






            share|improve this answer






























              3














              Avoid def, your life will be easier.



              Since you seem to know about @ifnextchar:



              documentclass[a4paper,12pt,fleqn]{article}

              % the imaginary unit, j for engineers and i for the rest of the world
              newcommandimaginaryunit{j}
              % in upright type as engineers do; also Euler's constant
              newcommandimunit{mathrm{imaginaryunit}}
              newcommandce{mathrm{e}}

              newcommand{fiximunit}{ifimaginaryunit j,fi}

              makeatletter
              newcommand{epowim}[1]{ce^{epowim@#1}}
              newcommand{epowim@}{@ifnextchar-{epowim@@}{epowim@@{fiximunit}}}
              newcommand{epowim@@}[1]{#1imunit}
              makeatother

              begin{document}

              begin{equation}
              epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
              qquad epowim{} qquad epowim{-}
              end{equation}

              end{document}


              Explanation: @ifnextchar- uses the next argument if - is found, the successive one otherwise, but without removing -. So if - is called the result will be



              epowim@@-alpha


              which passes - as argument to epowim@@. Otherwise epowim@@ is called with fiximunit as argument.



              This would not fail with epowim{} or epowim{-} to typeset ej and e−j respectively.



              A perhaps simpler implementation with xparse:



              documentclass[a4paper,12pt,fleqn]{article}

              usepackage{xparse}

              % the imaginary unit, j for engineers and i for the rest of the world
              newcommandimaginaryunit{j}
              % in upright type as engineers do; also Euler's constant
              newcommandimunit{mathrm{imaginaryunit}}
              newcommandce{mathrm{e}}

              newcommand{fiximunit}{ifimaginaryunit j,fi}

              NewDocumentCommand{epowim}{m}{ce^{powim#1}}
              NewDocumentCommand{powim}{t-}{IfBooleanTF{#1}{-imunit}{fiximunitimunit}}

              begin{document}

              begin{equation}
              epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
              qquad epowim{} qquad epowim{-}
              end{equation}

              end{document}


              enter image description here






              share|improve this answer




























                3












                3








                3







                Avoid def, your life will be easier.



                Since you seem to know about @ifnextchar:



                documentclass[a4paper,12pt,fleqn]{article}

                % the imaginary unit, j for engineers and i for the rest of the world
                newcommandimaginaryunit{j}
                % in upright type as engineers do; also Euler's constant
                newcommandimunit{mathrm{imaginaryunit}}
                newcommandce{mathrm{e}}

                newcommand{fiximunit}{ifimaginaryunit j,fi}

                makeatletter
                newcommand{epowim}[1]{ce^{epowim@#1}}
                newcommand{epowim@}{@ifnextchar-{epowim@@}{epowim@@{fiximunit}}}
                newcommand{epowim@@}[1]{#1imunit}
                makeatother

                begin{document}

                begin{equation}
                epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
                qquad epowim{} qquad epowim{-}
                end{equation}

                end{document}


                Explanation: @ifnextchar- uses the next argument if - is found, the successive one otherwise, but without removing -. So if - is called the result will be



                epowim@@-alpha


                which passes - as argument to epowim@@. Otherwise epowim@@ is called with fiximunit as argument.



                This would not fail with epowim{} or epowim{-} to typeset ej and e−j respectively.



                A perhaps simpler implementation with xparse:



                documentclass[a4paper,12pt,fleqn]{article}

                usepackage{xparse}

                % the imaginary unit, j for engineers and i for the rest of the world
                newcommandimaginaryunit{j}
                % in upright type as engineers do; also Euler's constant
                newcommandimunit{mathrm{imaginaryunit}}
                newcommandce{mathrm{e}}

                newcommand{fiximunit}{ifimaginaryunit j,fi}

                NewDocumentCommand{epowim}{m}{ce^{powim#1}}
                NewDocumentCommand{powim}{t-}{IfBooleanTF{#1}{-imunit}{fiximunitimunit}}

                begin{document}

                begin{equation}
                epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
                qquad epowim{} qquad epowim{-}
                end{equation}

                end{document}


                enter image description here






                share|improve this answer















                Avoid def, your life will be easier.



                Since you seem to know about @ifnextchar:



                documentclass[a4paper,12pt,fleqn]{article}

                % the imaginary unit, j for engineers and i for the rest of the world
                newcommandimaginaryunit{j}
                % in upright type as engineers do; also Euler's constant
                newcommandimunit{mathrm{imaginaryunit}}
                newcommandce{mathrm{e}}

                newcommand{fiximunit}{ifimaginaryunit j,fi}

                makeatletter
                newcommand{epowim}[1]{ce^{epowim@#1}}
                newcommand{epowim@}{@ifnextchar-{epowim@@}{epowim@@{fiximunit}}}
                newcommand{epowim@@}[1]{#1imunit}
                makeatother

                begin{document}

                begin{equation}
                epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
                qquad epowim{} qquad epowim{-}
                end{equation}

                end{document}


                Explanation: @ifnextchar- uses the next argument if - is found, the successive one otherwise, but without removing -. So if - is called the result will be



                epowim@@-alpha


                which passes - as argument to epowim@@. Otherwise epowim@@ is called with fiximunit as argument.



                This would not fail with epowim{} or epowim{-} to typeset ej and e−j respectively.



                A perhaps simpler implementation with xparse:



                documentclass[a4paper,12pt,fleqn]{article}

                usepackage{xparse}

                % the imaginary unit, j for engineers and i for the rest of the world
                newcommandimaginaryunit{j}
                % in upright type as engineers do; also Euler's constant
                newcommandimunit{mathrm{imaginaryunit}}
                newcommandce{mathrm{e}}

                newcommand{fiximunit}{ifimaginaryunit j,fi}

                NewDocumentCommand{epowim}{m}{ce^{powim#1}}
                NewDocumentCommand{powim}{t-}{IfBooleanTF{#1}{-imunit}{fiximunitimunit}}

                begin{document}

                begin{equation}
                epowim{alpha}qquad epowim{-alpha} qquad ce^{-imunitalpha}
                qquad epowim{} qquad epowim{-}
                end{equation}

                end{document}


                enter image description here







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited 3 hours ago

























                answered 4 hours ago









                egregegreg

                721k8719113210




                721k8719113210






























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