The FromMathContainer command extracts the contents of a MathContainer component and returns an unsimplified inert-form expression.

By extracting to an inert form you can avoid the automatic simplification and evaluation that is normally done on mathematical expressions.  For example, extracting "1+1" using DocumentTools:-Do or DocumentTools:-GetProperty will give you the answer 2, because Maple automatically simplifies expressions containing the addition of integer constants.  Using this command, the same "1+1" will give %+(1,1), where the terms are all present in a form that can be easily manipulated in a predictable way.  

For more details about the nature of inert form, see InertForm:-Parse.  For information on automatic simplification, refer to the Maple Expressions chapter of the Maple Programming Guide.

This function is part of the InertForm package, so it can be used in the short form FromMathContainer(..) only after executing the command with(InertForm). However, it can always be accessed through the long form of the command by using InertForm[FromMathContainer](..).

$\mathrm{Grading}:-\mathrm{Quiz}\left(''Simplify\; the\; following\; expression:''\,1\,\mathrm{`\%*`}\left(8\,\mathrm{`\%/`}\left(\mathrm{\%sqrt}\left(4\right)\,\mathrm{`\%^`}\left(4\,2\right)\right)\right)\,\mathrm{inertform}=\mathrm{true}\right)$

$\mathrm{InertForm}:-\mathrm{FromMathContainer}\left(''MCGeneric''\right)$

Error, (in InertForm:-FromMathContainer) Attempted to retrieve property of unknown component MCGeneric.

The InertForm[FromMathContainer] command was introduced in Maple 18.

For more information on Maple 18 changes, see Updates in Maple 18.