Import declarations
An import declaration takes the following form:
(import {import-set} ...)
An import declaration provides a way to import identifiers
exported by a library. Each import set names a set of bindings
from a library and possibly specifies local names for the
imported bindings. It takes one of the following forms:
library name
(only {import set} {identifier} ...)
(except {import set} {identifier} ...)
(prefix {import set} {identifier})
(rename {import set} ({identifier1} {identifier2}) ...)
In the first form, all of the identifiers in the named library's export
clauses are imported with the same names (or the exported names if
exported with rename). The additional import set
forms modify this set as follows:
only produces a subset of the given
import set including only the listed identifiers (after any
renaming). It is an error if any of the listed identifiers are
not found in the original set.
except produces a subset of the given
import set, excluding the listed identifiers (after any
renaming). It is an error if any of the listed identifiers are not
found in the original set.
rename modifies the given import set,
replacing each instance of identifier1 with identifier2.
It is an error if any of the listed
identifier1's are
not found in the original set.
prefix automatically renames all identifiers in
the given import set, prefixing each with the specified
identifier.
In a program or library declaration, it is an error to import the same
identifier more than once with different bindings, or to redefine or
mutate an imported binding with a definition
or with set!, or to refer to an identifier before it is imported.
However, a REPL should permit these actions.
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