# Creating custom notation

How does one generate custom symbols? For example, the physicist notation for the rotation is "nabla cross function". In this case however, Mathematica complains that the [esc]del[esc] symbol evaluates to the unary operator Del[], which of course cannot take a cross ([esc]*[esc]) after it, since a bracket is expected.

Although a correctly looking output is generated by

Prefix[f[a], "\[Del]\[Times]"]


the result cannot simply be assigned to an operation (Prefix[...] := ...) you can type in using the nicely readable [esc] commands I mentioned above. Is there some way of doing this, i.e. invoking completely custom functionality to (combinations of) existing symbols?

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Well, there's the Notation package... –  Ｊ. Ｍ. Jan 18 '12 at 1:12
Retagged from "Formatting and layout" tags to "Notation". I think this better describes this. –  Mike Bantegui Jan 18 '12 at 2:05
In case you may be interested in, there are three undocumented symbol \[Laplace] \[Divergence] \[Curl] may be useful. –  Silvia Jan 18 '12 at 23:27
@Silvia Although those aren't necessarily related to the question, they might prove pretty useful, thanks! –  David Jan 18 '12 at 23:33
You should use \[Cross] (ESC cross ESC) rather than \[Times], since it's conceptually a cross product, not scalar multiplication. –  Mechanical snail Nov 15 '12 at 21:29

Notation[ParsedBoxWrapper[$$\[Del] \(\[Cross] a_$$\)] \ \[DoubleLongLeftRightArrow] ParsedBoxWrapper[$$f[a_]$$]] does the trick, actually. –  Ｊ. Ｍ. Jan 18 '12 at 1:18