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Satisfying a One-Argument Test

When using one of the functions in Figure 17--3, the elements E of a sequence S are filtered not on the basis of the presence or absence of an object O under a two argument predicate, as with the functions described in section Satisfying a Two-Argument Test, but rather on the basis of a one argument predicate.

assoc-if member-if rassoc-if assoc-if-not member-if-not rassoc-if-not count-if nsubst-if remove-if count-if-not nsubst-if-not remove-if-not delete-if nsubstitute-if subst-if delete-if-not nsubstitute-if-not subst-if-not find-if position-if substitute-if find-if-not position-if-not substitute-if-not

Figure 17--3: Operators that have One-Argument Tests to be Satisfied

The element E_i might not be considered directly. If a :key argument is provided, it is a designator for a function of one argument to be called with each E_i as an argument, and yielding an object Z_i to be used for comparison. (If there is no :key argument, Z_i is E_i.)

Functions defined in this specification and having a name that ends in "-if" accept a first argument that is a designator for a function of one argument, Z_i. An E_i is said to satisfy the test if this :test function returns a generalized boolean representing true.

Functions defined in this specification and having a name that ends in "-if-not" accept a first argument that is a designator for a function of one argument, Z_i. An E_i is said to satisfy the test if this :test function returns a generalized boolean representing false.


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