Cfrgtkky

I want to create a math operator that is an integral with a square (square) stack onto it such that the integral is still formated the way that the operator int is. How do I do this?

documentclass{article}

usepackage{esint}

begin{document}



[ sqintlimits_0^1 x,mathrm dxneintlimits_0^1 x,mathrm dx ]           

[ scriptstylesqint_0^1 x,mathrm dxneint_0^1 x,mathrm dx ]     

[ scriptscriptstylesqint_0^1 x,mathrm dxneint_0^1 x,mathrm dx ]    



[ sqiintlimits_0^1 x,mathrm dxneiintlimits_0^1 x,mathrm dx ]     

[ scriptstylesqiint_0^1 x,mathrm dxneiint_0^1 x,mathrm dx ]    

[ scriptscriptstylesqiint_0^1 x,mathrm dxneiint_0^1 x,mathrm dx]

end{document}

Adapting Heiko Oberdiek's code in https://tex.stackexchange.com/a/171445/4427 is almost straightforward

documentclass[a5paper]{article}



usepackage{graphicx}



usepackage{amsmath}

usepackage{amssymb}





makeatletter

letDOTSIrelax % amsmath support for dots

newcommand*{sqint}{%

  DOTSI

  mathop{%

    mathpalette@LetterOnInt{square}%

  }%

  mkern-thinmuskip % thin space is inserted between two mathop

  int

}

newcommand*{@LetterOnInt}[2]{%

  sbox0{$#1intm@th$}%

  sbox2{$%

    ifx#1displaystyle

      textstyle

    else

      scriptscriptstyle

    fi

    #2%

  m@th$}%

  dimen@=.4dimexprht0+dp0relax

  ifdimdimexprht2+dp2relax>dimen@

    sbox2{resizebox*{!}{dimen@}{unhcopy2}}%

  fi

  dimen@=wd0 %

  ifdimwd2>dimen@

    dimen@=wd2 %

  fi

  rlap{hbox to dimen@{hfil

    $#1vcenter{copy2}m@th$%

  hfil}}%

  ifdimdimen@>wd0 %

    kern.5dimexprdimen@-wd0relax

  fi

}

makeatother



begin{document}



Take the regulated function $f$, we want to compare the Riemann integral,

$int_a^b f$

to the regulated integral $sqint_a^b f$ by taking

sequences of step

functions.



We will prove that

[

  sqint_a^b f = int_a^b f

]



[

  displaystyle      int_a^b f dots sqint_a^b f qquad

  textstyle         int_a^b f dots sqint_a^b f qquad

  scriptstyle       int_a^b f dots sqint_a^b f qquad

  scriptscriptstyle int_a^b f dots sqint_a^b f

]



end{document}

Tweaked for CM font.

documentclass{article}

usepackage{amssymb,graphicx}

newcommandsqint{mathchoice

  {raisebox{.75pt}{$scriptscriptstylesquare$}mkern-17.5mu}

  {raisebox{.75pt}{$scriptscriptstylesquare$}mkern-14mu}

  {scalebox{.8}{$scriptscriptstylesquare$}mkern-13mu}

  {scalebox{.55}{$scriptscriptstylesquare$}mkern-11mu}

  int}

begin{document}

$displaystylesqint_0^1 x,dxneint_0^1 x,dx$smallskip



$sqint_0^1 x,dxneint_0^1 x,dx$smallskip



$scriptstylesqint_0^1 x,dxneint_0^1 x,dx$smallskip



$scriptscriptstylesqint_0^1 x,dxneint_0^1 x,dx$

end{document}