### `++sand`

Soft-cast by odor

Soft-cast validity by odor.

Accepts
-------

`a` is a `++span` (`@ta`).

`b` is an atom.

Produces
--------

A `(unit @)`.

Source
------

    ++  sand                                                ::  atom sanity
      |=  a/@ta
      |=  b/@  ^-  (unit @)
      ?.(((sane a) b) ~ [~ b])
    ::

Examples
--------

    /~zod/try=> `(unit @ta)`((sand %ta) 'sym-som')
    [~ ~.sym-som]
    /~zod/try=> `(unit @ta)`((sand %ta) 'err!')
    ~



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