I am using Mathematica 11.3.0.0, 64 bit.

Here is my code:

Graphics[Thread[Circle[{{-1, 0}, {0, 0}, {1, 0}}, {0.5, 1.0, 0.5}]]]

Here is code as it looks in a notebook:

On mouseover on , {1, 0}:

However, when I evaluate that code I am getting the right output:

Questions

Why, although is , {1, 0} colored in red, does the expression evaluate correctly? Is it a bug? Or maybe I am doing something wrong?

  • Everything is fine. That's just the syntax highlighter. If it makes you feel better, you can use MapThread[Circle, {{{-1, 0}, {0, 0}, {1, 0}}, {0.5, 1.0, 0.5}}] instead. – Henrik Schumacher Sep 23 at 19:41
  • 1
    SyntaxInformation[Circle] gives {"ArgumentsPattern" -> {Optional[{_, _}], _., Optional[{_, _}]}}. That is, the first argument (if it is used) should be a list of two elements. – kglr Sep 23 at 19:41
  • 2
    Please do not use the bug tag unless it is confirmed by support or community. – Kuba Sep 23 at 19:41
SyntaxInformation[Circle] 

{"ArgumentsPattern" -> {Optional[{_, _}], ., Optional[{, _}]}}

That is, the first argument (if it is used) should be a list with two elements. Hence, the excess arguments are colored red by the syntax highlighter.

Is Circle[{{-1, 0}, {0, 0}, {1, 0}}, {0.5, 1.0, 0.5}] a valid input? I hope it is clear it is not.

Will Thread[Circle[{{-1, 0}, {0, 0}, {1, 0}}, {0.5, 1.0, 0.5}]] evaluate to something reasonable? It will but you don't want a front end to evaluate your code behind the hood to determine this. Consider consequences if that was something less trivial.

Related:

Why is this semicolon in red?

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