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12.19 data.range - Range

Module: data.range

A range object is an immutable sequence with O(1) indexed access to the elements, and each element may be computed procedurally. For example, a range of intergers between 0 and N can be trivially realized as a range, where i-th element is simply computed by identity. It is a lot more space-efficient than actually generating a sequence containing every number.

It also allows certain operations efficient, such as taking subsequence or appending sequences.

A range object can be used with :range qualifier in the srfi-42 eager comprehension (see Eager comprehensions).

A portable range object interface is defined in srfi-196. We implement the range object as a <sequence>, so that all sequence framework interface can be used on the ranges (see Sequence framework). We also provide some additional procedures that are not in srfi-196.

Classes

Class: <range>

Range object class. Internally we use several subclasses according to the nature of the range, but externally all ranges can be treated as an instance of <range>.

Class: <range-meta>

The metaclass of <range> class.

Constructors

Function: range length indexer

[SRFI-196] {data.range} Creates and returns a range of length length, whose i-th element (0 <= i < length)) is determined by a procedure indexer, which takes i as the sole argument and returns the corresponding element.

Note that indexer must run in O(1) time, and must be referentially transparent. The impelemntation may “expand” the range, that is, computes the element values into a flat vector internally.

(range->list (range 5 (^i (+ i 10))))
 ⇒ (10 11 12 13 14)
Function: numeric-range start end :optional step

[SRFI-196] {data.range} Creates and returns a range of integers starting from start (inclusive) and ending below end (exclusive), increasing with step. The default value of step is 1.

(range->list (numeric-range 2 6))
 ⇒ (2 3 4 5)

(range->list (numeric-range 0 5 2/3))
 ⇒ (0 2/3 4/3 2 8/3 10/3 4 14/3)
Function: iota-range length :optional start step

[SRFI-196] {data.range} Creates and returns a range of integers. Total length of the range is length. The range starts from start (default 0), and increased with step (default 1).

(range->list (iota-range 5))
  ⇒ (0 1 2 3 4)

(range->list (iota-range 7 1 -1/7))
  ⇒ (1 6/7 5/7 4/7 3/7 2/7 1/7)
Function: vector-range vec :optional start end

[SRFI-196+] {data.range} Returns a range over the given vector vec. The vector is kept in the range, so you shouldn’t mutate vec.

The optional start and end arguments limits the range of the vector to be used. They are Gauche’s extension and not in srfi-196.

(range->list (vector-range '#(a b c)))
  ⇒ (a b c)

(range->list (vector-range '#(a b c d e) 1 4))
  ⇒ (b c d)
Function: uvector-range uvec :optional start end

{data.range} Returns a range over the given uniform vector uvec. The uniform vector is kept in the range, so you shouldn’t mutate uvec.

The optional start and end arguments limits the range of the uniorm vector to be used.

Function: string-range str :optional start end

[SRFI-196] {data.range} Returns a range over each character in the given string str. The string is kept in the range, so you shouldn’t mutate str.

The optional start and end arguments limits the range of the vector to be used. They are Gauche’s extension and not in srfi-196.

(range->list (string-range "abc"))
  ⇒ (#\a #\b #\c)

(range->list (string-range "abcde" 1 4))
  ⇒ (#\b #\c #\d)
Function: range-append range …

[SRFI-196] {data.range} Returns a new range that walks over concatenation of the given ranges.

Function: range-reverse range :optional start end

[SRFI-196+] {data.range} Returns a new range that walks over the elements of range, but in reverse order.

The optional start and end arguments limits the range of the vector to be used. They are Gauche’s extension and not in srfi-196.

(range->list (range-reverse (string-range "abc")))
  ⇒ (#\c #\b #\a)

(range->list (range-reverse (string-range "abcdef" 1 4)))
  ⇒ (#\d #\c #\b)

Predicates

Function: range? obj

[SRFI-196] {data.range} Returns true iff obj is a range.

Function: range=? elt= range …

[SRFI-196] {data.range} Returns true iff all ranges have the same length, and any pair of corresponding elements in the given ranges are equal in terms of elt= predicate.

As edge cases, when zero or one range is given, #t is returned.

(range=? eqv? (numeric-range 0 5)
              (iota-range 5)
              (vector-range '#(0 1 2 3 4)))
  ⇒ #t

Accessors

Function: range-length range

[SRFI-196] {data.range} Returns the length of range.

Function: range-ref range i :optional fallback

[SRFI-196+] {data.range} Returns the i-th element of range. The index i must be an exact integer.

If i is negative, or greater than or equal to the length of range, fallback is returned if given, or an error is signaled. The fallback argument is Gauche’s extension and not in srfi-196.

Function: range-first range :optional fallback

[SRFI-196+] {data.range} Returns the first element of range.

If the range is empty, fallback is returned if given, or an error is signaled. The fallback argument is Gauche’s extension and not in srfi-196.

Function: range-last range :optional fallback

[SRFI-196+] {data.range} Returns the last element of range.

If the range is empty, fallback is returned if given, or an error is signaled. The fallback argument is Gauche’s extension and not in srfi-196.

Iteration

Function: range-split-at range k

[SRFI-196] {data.range} Returns two ranges, the first one with elements before k-th elements of range, and the second one with k-th elements and after of range.

Function: subrange range start end

[SRFI-196] {data.range} Returns a new range that contains start-th (inclusive) to end-th (exclusive) elements of range.

Function: range-segment range len

[SRFI-196] {data.range}

Function: range-take range count
Function: range-take-right range count

[SRFI-196] {data.range}

Function: range-drop range count
Function: range-drop-range range count

[SRFI-196] {data.range}

Function: range-count pred range range2 …

[SRFI-196] {data.range}

Function: range-any pred range range2 …

[SRFI-196] {data.range}

Function: range-every pred range range2 …

[SRFI-196] {data.range}

Function: range-map proc range range2 …
Function: range-map->list proc range range2 …
Function: range-map->vector proc range range2 …

[SRFI-196] {data.range}

Function: range-for-each pred range range2 …

[SRFI-196] {data.range}

Function: range-filter-map pred range range2 …
Function: range-filter-map->list pred range range2 …

[SRFI-196] {data.range}

Function: range-filter pred range
Function: range-filter->list pred range
Function: range-remove pred range
Function: range-remove->list pred range

[SRFI-196] {data.range}

Function: range-fold kons knil range range2 …
Function: range-fold-right kons knil range range2 …

[SRFI-196] {data.range}

Searching

Function: range-index pred range range2 …
Function: range-index-right pred range range2 …

[SRFI-196] {data.range}

Function: range-take-while pred range
Function: range-take-while-right pred range

[SRFI-196] {data.range}

Function: range-drop-while pred range
Function: range-drop-while-right pred range

[SRFI-196] {data.range}

Conversion

Function: range->list range

[SRFI-196] {data.range}

Function: range->vector range

[SRFI-196] {data.range}

Function: range->string range

[SRFI-196] {data.range}

Function: vector->range vec :optional start end

[SRFI-196] {data.range}

Function: range->generator range :optional start end

[SRFI-196] {data.range}


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