• ← ParentForm

$PrintForms

$PrintForms

contains the current list of general-purpose “Forms” formatters.

It is updated automatically when new forms are defined via setting Format in the the left-hand-side of a delayed assignment.

• • $PrintForms

Suppose now that we want to add a new format MyForm. Initially, it does not belong to $PrintForms:

• • MemberQ[$PrintForms, MyForm]

Now, let's define a format rule:

• • Format[F[x_], MyForm] := "F<<" <> ToString[x] <> ">>"

Now, the new format belongs to the $PrintForms list

• • MemberQ[$PrintForms, MyForm]