SELECTC - SELECT on constant

[KAPLAN]

This function lies somewhere between SELECTQ and SELECT (which previously
existed but wasn't documented).  With SELECTC, the selection keys are
evaluated when called from interpreted code, just like SELECT.  Unlike
SELECT, the keys are also evaluated at compile-time to form a SELECTQ.

The form of a selection clause is either 
1.  an atom or list of atoms, whose values are treated as the keys.
2.  a list of lists, the elements of which are forms whose values are treated
as the keys.

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