I am typing up a set of notes for the Riemann Stieltjes integral. For reasons beyond the scope of the question, I would like to start with defining the Darboux's integral and then formulate Riemann's definition and show that they are equivalent.

During the intermediate steps, provisionally, I would like to define the Riemann integral, the R-integral. To avoid mixing of symbols, I have in mind a symbol like \oint but with a R instead of the circle.

I am not aware of what the TeX code for the symbol would be.

Any help would be appreciated.

1 Answer 1


You may try with the following code:

  {\mkern2.5mu R}
  {\scriptstyle R}
  {\scriptscriptstyle R}
  {\scriptscriptstyle R}
\left|\Rint_a^b f\right|\textstyle\left|\Rint_a^b f\right|_{\left|\Rint_a^b f\right|}

enter image description here

The absolute value is only for demonstration purpose.

The main problem here is to adapt the R to the various formula styles, so we use \mathchoice. With \mathrlap we can build a zero width box that will not contribute to the width of the formula. Since \int is an operator, we put this zero width formula into a \mathop, then \! is used to remove the space that TeX inserts between two consecutive Operator atoms.

Next we define \pushR, that's simply a space in display style, followed by a normal size R. In text and lower styles we simply put a reduced size R. Probably the result will not be nice in \scriptscriptstyle, but it doesn't seem so important.

The same idea can be used for the principal value integral:


enter image description here

  • Unicode-math provides \fint and \intbar to print Principal Value of integral, but these do not scale as \int. Commented Oct 28, 2016 at 5:11

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