3.14.2 Streams
A stream is a kind of sequence that supports
functional iteration via stream-first and
stream-rest. The stream-cons form constructs a lazy
stream, but plain lists can be used as stream, and functions such as
in-range and in-naturals also create streams.
Returns
#t if
v can be used as a
stream,
#f otherwise.
Returns #f if s has no elements, #f
otherwise.
Returns the value(s) of the first element in s.
Returns a stream that is equivalent to s without its first
element.
Produces a lazy stream for which
stream-first forces the
evaluation of
first-expr to produce the first element of
the stream, and
stream-rest forces the evaluation of
rest-expr to produce a stream for the rest of the returned
stream.
The first element of the stream as produced by first-expr
must be a single value. The rest-expr must produce a stream
when it is evaluated, otherwise the exn:fail:contract? exception is raised.
Returns a sequence that is equivalent to s.
An
in-stream application can provide better performance for streams iteration when it appears directly in a
for clause.
A stream with no elements.
Returns a list whose elements are the elements of s, each
of which must be a single value. If s is infinite, this
function does not terminate.
Returns the number of elements of s. If s is
infinite, this function does not terminate.
In the case of lazy streams, this function forces evaluation only of
the sub-streams, and not the stream’s elements.
Returns the ith element of s (which may be
multiple values).
Returns a stream equivalent to s, except that the first
i elements are omitted.
In case extracting elements from s involves a side effect,
they will not be extracted until the first element is extracted from
the resulting stream.
Returns a stream that contains all elements of each stream in the
order they appear in the original streams. The new stream is
constructed lazily, while the last given stream is used in the tail
of the result.
Returns a stream that contains f applied to each element of
s. The new stream is constructed lazily.
Returns #t if f returns a true result on every
element of s. If s is infinite and f
never returns a false result, this function does not terminate.
Returns #t if f returns a true result on some
element of s. If s is infinite and f
never returns a true result, this function does not terminate.
Applies f to each element of s. If s is
infinite, this function does not terminate.
Folds f over each element of s with i as
the initial accumulator. If s is infinite, this function
does not terminate.
Returns the number of elements in s for which f
returns a true result. If s is infinite, this function
does not terminate.
Returns a stream whose elements are the elements of s for
which f returns a true result. Although the new stream is
constructed lazily, if s has an infinite number of elements
where f returns a false result in between two elements
where f returns a true result, then operations on this
stream will not terminate during the infinite sub-stream.
Returns a stream whose elements are the elements of s, but
with e between each pair of elements in s. The
new stream is constructed lazily.
To supply method implementations, the #:methods keyword
should be used in a structure type definition. The following three
methods should be implemented:
A deprecated structure type property used to define custom
extensions to the stream API. Use
gen:stream instead.
Accepts a vector of three procedures taking the same arguments as
the methods in
gen:stream.