arithmetic operations with \ifthenelse

Question

Is there a way to add arithmetic operations to \ifthenelse statements? Here is a minimal (non)example:

\documentclass{amsart} \usepackage{tikz, ifthen} \begin{document} \begin{tikzpicture} \foreach \a in {-6,...,6} { \foreach \b in {-6,...,6} { \ifthenelse{ (\a + \b) < 4 } { \node at ( (\a, \b ) {(\a, \b)}; } {} } } \end{tikzpicture} \end{document}

It is not working because \ifthenelse does not allow \a+\b.

Bonus question: Is there a way to e.g. define `\c` = `\a` + `\b` in advance so I can use `\c` elsewhere, in `\ifthenelse` and subsequence `\draw` commands?

EDIT:

Actually what I needed is \a + 1.414*\b < 4 AND \a - 1.414*\b > 0. I thought I could handle the rest once I know how to insert arithmetic operations into \ifthenelse, but apparently it's more complicated than that. Apologies for the mixup and thanks for your help.

To set \c to \a + \b, just use \pgfmathtruncatemacro{\c}{\a+\b} (or \pgfmathsetmacro{\c}{\a+\b} if you need floating numbers instead of integers). — Jasper Habicht
– Jasper Habicht, Commented Nov 23 at 18:21
I wrote an answer to your updated question, but realised your edit invalidates existing answers. please don't do this. instead, ask another question and link this one. if you do so, I will re-post my answer there. (I have deleted my answer here.) — cfr
– cfr, Commented Nov 24 at 5:05
@cfr: Apologies about the editing. I just created a new post linking this one. Thanks for your help. — underflow
– underflow, Commented Nov 24 at 6:51

Jasper Habicht · Accepted Answer · 2025-11-24 06:01:05Z

For simple integer comparisons (which you seemed to need based on in your original question), using the relevant expl3 function with \UseName as wrapper is probably the easiest solution for this:

\documentclass{amsart} \usepackage{tikz} \begin{document} \begin{tikzpicture} \foreach \a in {-6,...,6} { \foreach \b in {-6,...,6} { \UseName{int_compare:nNnT}{ \a + \b } < { 4 } { \node at ( (\a, \b ) {(\a, \b)}; } } } \end{tikzpicture} \end{document}

For a more general solution that also allows for floating point numbers, use PGF's math capabilities:

\documentclass{amsart} \usepackage{tikz} \begin{document} \begin{tikzpicture} \foreach \a in {-6,...,6} { \foreach \b in {-6,...,6} { \pgfmathsetmacro{\numc}{ \a + 1.414*\b < 4 && \a - 1.414*\b > 0 } \ifnum\numc=1\relax \node at ( (\a, \b ) {(\a, \b)}; \fi } } \end{tikzpicture} \end{document}

Thanks @Jasper. Actually I need to handle floating points, and I have a boolean operation -- cf end the edited OP. How might I modify your codes to handle these? Apologies for not stating these at the outside (it didn't occur to me that floating & boolean would cause problems). — underflow
– underflow, Commented Nov 23 at 21:53
@underflow See my edit: This is the general way, you would solve such things using PGF's built-in math. — Jasper Habicht
– Jasper Habicht, Commented Nov 24 at 5:50

Werner · Accepted Answer · 2025-11-23 18:20:25Z

Use \inteval (for integer) or \fpeval (for floating point) arithmetic.

\documentclass{article} \usepackage{tikz} \begin{document} \begin{tikzpicture} \foreach \numA in {-6,...,6}{% \foreach \numB in {-6,...,6}{% \ifnum \inteval{\numA + \numB} < 4 \node at ( (\numA, \numB ) {$(\numA, \numB)$}; \fi }% }% \end{tikzpicture} \begin{tikzpicture} \foreach \numA in {-6,...,6}{% \foreach \numB in {-6,...,6}{% \edef\numC{\inteval{\numA + \numB}}% c = a + b \ifnum \numC < 4 \node at ( (\numA, \numB ) {$(\numA, \numB)$}; \fi }% }% \end{tikzpicture} \end{document}

Also, try to avoid single-character macros like \a, \b, \c, as they are often used for other things.

Thanks@Werner. Actually what I needed is (\numA + 1.414*\numB) < 4 AND (\numA - 1.414*\numB)> 0. When I put in the decimals I got errors, and without the decmial \ifnum ignores the \and. What is the correct syntax for handling the decmial PLUS the \and? I have edited my post to reflect this. Thanks! — underflow
– underflow, Commented Nov 23 at 21:44
@underflow: \ifnum\fpeval{(\numA + sqrt(2) * \numB > 4) && (\numA - sqrt(2) * \numB < 0)} = 1 <true> \fi. Look at the xfp documentation for an overview of all the options provided. — Werner
– Werner ♦, Commented Nov 24 at 17:45

Stack Exchange Network

arithmetic operations with \ifthenelse

Bonus question: Is there a way to e.g. define `\c` = `\a` + `\b` in advance so I can use `\c` elsewhere, in `\ifthenelse` and subsequence `\draw` commands?

2 Answers 2

You must log in to answer this question.

Linked

Hot Network Questions

arithmetic operations with \ifthenelse

Bonus question: Is there a way to e.g. define \c = \a + \b in advance so I can use \c elsewhere, in \ifthenelse and subsequence \draw commands?

2 Answers 2

You must log in to answer this question.

Linked

Related

Hot Network Questions

Bonus question: Is there a way to e.g. define `\c` = `\a` + `\b` in advance so I can use `\c` elsewhere, in `\ifthenelse` and subsequence `\draw` commands?