The predicate language allows the user to define simple predicates (Boolean-valued functions) that Dune can evaluate. Here is a semiformal specification of the predicate language:
pred ::= (and
The exact meaning of
:standard and the nature of
on the context. For example, in the case of the dirs, an
element corresponds to file glob patterns. Another example is the user
action (with-accepted-exit-codes …), where an
element corresponds to a literal integer.