I am currently trying to make a FormPage that plots a Molecule and I try to add a possibility to input a custom Molecule.

Entering the data for a Molecule makes Mathematica crash.

Code: FormPage["m"->Molecule,MoleculePlot@#m&]

An input that works is e.g. Benzene but things like {"H","H"},{Bond[{1,2}]} made Mathematica crash.

It doesn't crash anymore but I get MoleculePlot: Argument Molecule[{"H","H"},{Bond[{1,2}]}] is not a valid molecule.


1 Answer 1


You have to specify that the input can be a Mathematica expression. However, {"H", "H"}, {Bond[{1, 2}]} is not really a valid expression, and it must be wrapped in another list {{"H", "H"}, {Bond[{1, 2}]}}. Then you can do it as following:

FormPage["m" -> ToExpression, MoleculePlot[Molecule @@ #m] &]


The drawback now is that you have to input "benzene" with the quotemarks. You can solve this by setting m to be a string, then checking if it includes curly braces, and parse it to expression afterwards with ToExpression. And since we are already making a somehow unelegant workaround, let's also manually include the curly brackets.

FormPage["m" -> String,
   Molecule @@ 
    If[StringContainsQ[#m, "{"], 
     ToExpression["{" <> #m <> "}"], {#m}]] &]

FormPage with parsing expression


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