I have made this type mistake so many times:


as opposed to the intended but still correct syntax


And, the mistake doesn't jump out at me--especially when there are more than several lines of code. Syntax coloring would help me identify the mistake quickly.

Is it possible to make a custom syntax coloring for "=", "==", and "==="?

  • 1
    $\begingroup$ SyntaxInformation[Which] seems to indicate that equal signs of odd-index arguments should be colored. But they're not. The setting "ColorEqualSigns" -> OddQ is not documented and seems not to work. A bug? Ask WRI. $\endgroup$
    – Michael E2
    Commented May 25, 2023 at 16:13
  • 1
    $\begingroup$ Possible duplicate?: mathematica.stackexchange.com/questions/59755/… -- It certainly implies that you're out of luck. Unless there's a hack around the bug. $\endgroup$
    – Michael E2
    Commented May 25, 2023 at 16:22
  • 1
    $\begingroup$ According to this answer, "ColorEqualSigns" -> System`Odd should color = at odd-index arguments, but it colors only the first argument. (So it's a known bug since 2017.) $\endgroup$
    – Michael E2
    Commented May 25, 2023 at 16:26
  • $\begingroup$ Thanks @MichaelE2. Useful to know that this is potentially interesting enough that somebody wanted it in 2017. Fingers crossed for a future release. $\endgroup$ Commented May 25, 2023 at 18:35
  • 1
    $\begingroup$ If more people ask for it to be fixed, that will make it seem more valuable to WRI to fix it. $\endgroup$
    – Michael E2
    Commented May 25, 2023 at 18:38

1 Answer 1


1. Syntax Coloring (partially working)

Under menu Edit > Preferences > Appearance > Syntax Coloring > Errors and Warnings, turn on Possible unwanted assignments. This will make = in Solve red.

enter image description here

However, as explained by @Itai Seggev, this doesn't work for Which due to a bug. It can be fixed, but it will unfortunately work only for the first argument (which is apparently also a known but not yet fixed bug):

SyntaxInformation[Which] = SyntaxInformation[Which] /.
  ("ColorEqualSigns" -> _) -> ("ColorEqualSigns" -> System`Odd);

enter image description here

2. Operator Rendering

For versions 12.3.1+, you can use OperatorRenderings to set more distinct characters for Set, Equal and SameQ. There is a whole variety of interesting Unicode symbols that resemble =, such as = ﹦ ⩶ ≝ ⌯ ⩸. You can probably find your own combination of symbols which will help you in easier differentiation between them.

opR = AbsoluteCurrentValue[$FrontEndSession, {StyleHints, "OperatorRenderings"}];
opR["="] = "≜";
opR["=="] = "≡";
opR["==="] = "≣";
CurrentValue[$FrontEndSession, {StyleHints, "OperatorRenderings"}] = opR;

Animation of typing

  • 2
    $\begingroup$ Thanks. Not just solve, but also this: Which[a = b, a, True, b] The Solve example wasn't a good example of what I wanted--I'll edit Would you mind deleting your answer so the question gets attention? $\endgroup$ Commented May 25, 2023 at 15:30
  • $\begingroup$ I have edited the answer so that it more clearly shows its flaws. However, I believe it still does partially answer your question. Obviously, you have every right to downvote it or/and not accept it :) (Or give a bounty to the question for more attention ...) $\endgroup$
    – Domen
    Commented May 25, 2023 at 21:25
  • $\begingroup$ Excellent! Accepted as answered. Thanks. $\endgroup$ Commented May 26, 2023 at 13:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.