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(require 'array) or (require 'srfi-63)
Returns #t if the obj is an array, and #f if not.
Note: Arrays are not disjoint from other Scheme types.
Vectors and possibly strings also satisfy array?.
A disjoint array predicate can be written:
(define (strict-array? obj) (and (array? obj) (not (string? obj)) (not (vector? obj))))
Returns #t if obj1 and obj2 have the same rank and dimensions and the
corresponding elements of obj1 and obj2 are equal?.
equal? recursively compares the contents of pairs, vectors, strings, and
arrays, applying eqv? on other objects such as numbers
and symbols. A rule of thumb is that objects are generally equal? if
they print the same. equal? may fail to terminate if its arguments are
circular data structures.
(equal? 'a 'a) ⇒ #t
(equal? '(a) '(a)) ⇒ #t
(equal? '(a (b) c)
'(a (b) c)) ⇒ #t
(equal? "abc" "abc") ⇒ #t
(equal? 2 2) ⇒ #t
(equal? (make-vector 5 'a)
(make-vector 5 'a)) ⇒ #t
(equal? (make-array (A:fixN32b 4) 5 3)
(make-array (A:fixN32b 4) 5 3)) ⇒ #t
(equal? (make-array '#(foo) 3 3)
(make-array '#(foo) 3 3)) ⇒ #t
(equal? (lambda (x) x)
(lambda (y) y)) ⇒ unspecified
Returns the number of dimensions of obj. If obj is not an array, 0 is returned.
Returns a list of dimensions.
(array-dimensions (make-array '#() 3 5)) ⇒ (3 5)
Creates and returns an array of type prototype with dimensions k1, … and filled with elements from prototype. prototype must be an array, vector, or string. The implementation-dependent type of the returned array will be the same as the type of prototype; except if that would be a vector or string with rank not equal to one, in which case some variety of array will be returned.
If the prototype has no elements, then the initial contents of the returned array are unspecified. Otherwise, the returned array will be filled with the element at the origin of prototype.
create-array is an alias for make-array.
make-shared-array can be used to create shared subarrays of other
arrays. The mapper is a function that translates coordinates in
the new array into coordinates in the old array. A mapper must be
linear, and its range must stay within the bounds of the old array, but
it can be otherwise arbitrary. A simple example:
(define fred (make-array '#(#f) 8 8))
(define freds-diagonal
(make-shared-array fred (lambda (i) (list i i)) 8))
(array-set! freds-diagonal 'foo 3)
(array-ref fred 3 3)
⇒ FOO
(define freds-center
(make-shared-array fred (lambda (i j) (list (+ 3 i) (+ 3 j)))
2 2))
(array-ref freds-center 0 0)
⇒ FOO
list must be a rank-nested list consisting of all the elements, in row-major order, of the array to be created.
list->array returns an array of rank rank and type proto consisting of all the
elements, in row-major order, of list. When rank is 0, list is the lone
array element; not necessarily a list.
(list->array 2 '#() '((1 2) (3 4)))
⇒ #2A((1 2) (3 4))
(list->array 0 '#() 3)
⇒ #0A 3
Returns a rank-nested list consisting of all the elements, in
row-major order, of array. In the case of a rank-0 array, array->list returns
the single element.
(array->list #2A((ho ho ho) (ho oh oh)))
⇒ ((ho ho ho) (ho oh oh))
(array->list #0A ho)
⇒ ho
vect must be a vector of length equal to the product of exact nonnegative integers dim1, ….
vector->array returns an array of type proto consisting of all the elements, in
row-major order, of vect. In the case of a rank-0 array, vect has a
single element.
(vector->array #(1 2 3 4) #() 2 2)
⇒ #2A((1 2) (3 4))
(vector->array '#(3) '#())
⇒ #0A 3
Returns a new vector consisting of all the elements of array in row-major order.
(array->vector #2A ((1 2)( 3 4)))
⇒ #(1 2 3 4)
(array->vector #0A ho)
⇒ #(ho)
Returns #t if its arguments would be acceptable to
array-ref.
Returns the (k1, …) element of array.
Stores obj in the (k1, …) element of array. The value returned
by array-set! is unspecified.
These functions return a prototypical uniform-array enclosing the optional argument (which must be of the correct type). If the uniform-array type is supported by the implementation, then it is returned; defaulting to the next larger precision type; resorting finally to vector.
Returns an inexact 128.bit flonum complex uniform-array prototype.
Returns an inexact 64.bit flonum complex uniform-array prototype.
Returns an inexact 32.bit flonum complex uniform-array prototype.
Returns an inexact 16.bit flonum complex uniform-array prototype.
Returns an inexact 128.bit flonum real uniform-array prototype.
Returns an inexact 64.bit flonum real uniform-array prototype.
Returns an inexact 32.bit flonum real uniform-array prototype.
Returns an inexact 16.bit flonum real uniform-array prototype.
Returns an exact 128.bit decimal flonum rational uniform-array prototype.
Returns an exact 64.bit decimal flonum rational uniform-array prototype.
Returns an exact 32.bit decimal flonum rational uniform-array prototype.
Returns an exact binary fixnum uniform-array prototype with at least 64 bits of precision.
Returns an exact binary fixnum uniform-array prototype with at least 32 bits of precision.
Returns an exact binary fixnum uniform-array prototype with at least 16 bits of precision.
Returns an exact binary fixnum uniform-array prototype with at least 8 bits of precision.
Returns an exact non-negative binary fixnum uniform-array prototype with at least 64 bits of precision.
Returns an exact non-negative binary fixnum uniform-array prototype with at least 32 bits of precision.
Returns an exact non-negative binary fixnum uniform-array prototype with at least 16 bits of precision.
Returns an exact non-negative binary fixnum uniform-array prototype with at least 8 bits of precision.
Next: Array Mapping, Previous: Arrays, Up: Data Structures [Contents][Index]
(require 'subarray)
selects a subset of an array. For 0 <= j < n, selectj is either an integer, a list of two integers within the range for the jth index, or #f.
When selectj is a list of two integers, then the jth index is restricted to that subrange in the returned array.
When selectj is #f, then the full range of the jth index is accessible in the returned array. An elided argument is equivalent to #f.
When selectj is an integer, then the rank of the returned array is less than array, and only elements whose jth index equals selectj are shared.
> (define ra '#2A((a b c) (d e f))) #<unspecified> > (subarray ra 0 #f) #1A(a b c) > (subarray ra 1 #f) #1A(d e f) > (subarray ra #f 1) #1A(b e) > (subarray ra '(0 1) #f) #2A((a b c) (d e f)) > (subarray ra #f '(0 1)) #2A((a b) (d e)) > (subarray ra #f '(1 2)) #2A((b c) (e f)) > (subarray ra #f '(2 1)) #2A((c b) (f e))
Arrays can be reflected (reversed) using subarray:
> (subarray '#1A(a b c d e) '(4 0)) #1A(e d c b a)
Returns a subarray sharing contents with array except for slices removed from either side of each dimension. Each of the trims is an exact integer indicating how much to trim. A positive s trims the data from the lower end and reduces the upper bound of the result; a negative s trims from the upper end and increases the lower bound.
For example:
(array-trim '#(0 1 2 3 4) 1) ⇒ #1A(1 2 3 4) (array-trim '#(0 1 2 3 4) -1) ⇒ #1A(0 1 2 3) (require 'array-for-each) (define (centered-difference ra) (array-map ra - (array-trim ra 1) (array-trim ra -1))) (centered-difference '#(0 1 3 5 9 22)) ⇒ #(1 2 2 4 13)
Next: Array Interpolation, Previous: Subarrays, Up: Data Structures [Contents][Index]
(require 'array-for-each)
array1, … must have the same number of dimensions as array0 and have a range for each index which includes the range for the corresponding index in array0. proc is applied to each tuple of elements of array1 … and the result is stored as the corresponding element in array0. The value returned is unspecified. The order of application is unspecified.
array2, … must have the same number of dimensions as array1 and have a range for each index which includes the range for the corresponding index in array1. proc is applied to each tuple of elements of array1, array2, … and the result is stored as the corresponding element in a new array of type prototype. The new array is returned. The order of application is unspecified.
proc is applied to each tuple of elements of array0 … in row-major order. The value returned is unspecified.
Returns an array of lists of indexes for array such that, if li is a list of indexes for which array is defined, (equal? li (apply array-ref (array-indexes array) li)).
applies proc to the indices of each element of array in turn. The value returned and the order of application are unspecified.
One can implement array-index-map! as
(define (array-index-map! ra fun) (array-index-for-each ra (lambda is (apply array-set! ra (apply fun is) is))))
applies proc to the indices of each element of array in turn, storing the result in the corresponding element. The value returned and the order of application are unspecified.
One can implement array-indexes as
(define (array-indexes array)
(let ((ra (apply make-array '#() (array-dimensions array))))
(array-index-map! ra (lambda x x))
ra))
Another example:
(define (apl:index-generator n)
(let ((v (make-vector n 1)))
(array-index-map! v (lambda (i) i))
v))
Copies every element from vector or array source to the corresponding element of destination. destination must have the same rank as source, and be at least as large in each dimension. The order of copying is unspecified.
Next: Association Lists, Previous: Array Mapping, Up: Data Structures [Contents][Index]
(require 'array-interpolate)
ra must be an array of rank j containing numbers. interpolate-array-ref returns a
value interpolated from the nearest j-dimensional cube of elements
of ra.
(interpolate-array-ref '#2A:fixZ32b((1 2 3) (4 5 6)) 1 0.1)
==> 4.1
(interpolate-array-ref '#2A:fixZ32b((1 2 3) (4 5 6)) 0.5 0.25)
==> 2.75
ra1 and ra2 must be numeric arrays of equal rank. resample-array! sets ra1 to
values interpolated from ra2 such that the values of elements at the
corners of ra1 and ra2 are equal.
(define ra (make-array (A:fixZ32b) 2 2)) (resample-array! ra '#2A:fixZ32b((1 2 3) (4 5 6))) ra ==> #2A:fixZ32b((1 3) (4 6)) (define ra (make-array (A:floR64b) 3 2)) (resample-array! ra '#2A:fixZ32b((1 2 3) (4 5 6))) ra ==> #2A:floR64b((1.0 3.0) (2.5 4.5) (4.0 6.0))
Next: Byte, Previous: Array Interpolation, Up: Data Structures [Contents][Index]
(require 'alist)
Alist functions provide utilities for treating a list of key-value pairs as an associative database. These functions take an equality predicate, pred, as an argument. This predicate should be repeatable, symmetric, and transitive.
Alist functions can be used with a secondary index method such as hash tables for improved performance.
Returns an association function (like assq, assv, or
assoc) corresponding to pred. The returned function
returns a key-value pair whose key is pred-equal to its first
argument or #f if no key in the alist is pred-equal to the
first argument.
Returns a procedure of 2 arguments, alist and key, which
returns the value associated with key in alist or #f if
key does not appear in alist.
Returns a procedure of 3 arguments, alist, key, and value, which returns an alist with key and value associated. Any previous value associated with key will be lost. This returned procedure may or may not have side effects on its alist argument. An example of correct usage is:
(define put (alist-associator string-ci=?)) (define alist '()) (set! alist (put alist "Foo" 9))
Returns a procedure of 2 arguments, alist and key, which returns an alist with an association whose key is key removed. This returned procedure may or may not have side effects on its alist argument. An example of correct usage is:
(define rem (alist-remover string-ci=?)) (set! alist (rem alist "foo"))
Returns a new association list formed by mapping proc over the keys and values of alist. proc must be a function of 2 arguments which returns the new value part.
Applies proc to each pair of keys and values of alist. proc must be a function of 2 arguments. The returned value is unspecified.
Next: Byte/Number Conversions, Previous: Association Lists, Up: Data Structures [Contents][Index]
(require 'byte)
Some algorithms are expressed in terms of arrays of small integers. Using Scheme strings to implement these arrays is not portable vis-a-vis the correspondence between integers and characters and non-ascii character sets. These functions abstract the notion of a byte.
k must be a valid index of bytes. byte-ref returns byte k of bytes using
zero-origin indexing.
k must be a valid index of bytes, and byte must be a small
nonnegative integer. byte-set! stores byte in element k of bytes and
returns an unspecified value.
make-bytes returns a newly allocated byte-array of length k. If byte is
given, then all elements of the byte-array are initialized to byte,
otherwise the contents of the byte-array are unspecified.
bytes-length returns length of byte-array bytes.
Returns a newly allocated byte-array composed of the small nonnegative arguments.
list->bytes returns a newly allocated byte-array formed from the small
nonnegative integers in the list bytes.
bytes->list returns a newly allocated list of the bytes that make up the
given byte-array.
Bytes->list and list->bytes are inverses so far as
equal? is concerned.
Returns a new string formed from applying integer->char to
each byte in bytes->string. Note that this may signal an error for bytes
having values between 128 and 255.
Returns a new byte-array formed from applying char->integer
to each character in string->bytes. Note that this may signal an error if an
integer is larger than 255.
Returns a newly allocated copy of the given bytes.
bytes must be a bytes, and start and end must be exact integers satisfying
subbytes returns a newly allocated bytes formed from the bytes of
bytes beginning with index start (inclusive) and ending with index
end (exclusive).
Reverses the order of byte-array bytes.
Returns a newly allocated bytes-array consisting of the elements of bytes in reverse order.
Input and output of bytes should be with ports opened in binary
mode (see Input/Output). Calling open-file with ’rb or
’wb modes argument will return a binary port if the Scheme
implementation supports it.
Writes the byte byte (not an external representation of the byte) to
the given port and returns an unspecified value. The port argument may
be omitted, in which case it defaults to the value returned by
current-output-port.
Returns the next byte available from the input port, updating the port
to point to the following byte. If no more bytes are available, an
end-of-file object is returned. port may be omitted, in which case it
defaults to the value returned by current-input-port.
When reading and writing binary numbers with read-bytes and
write-bytes, the sign of the length argument determines the
endianness (order) of bytes. Positive treats them as big-endian,
the first byte input or output is highest order. Negative treats
them as little-endian, the first byte input or output is the lowest
order.
Once read in, SLIB treats byte sequences as big-endian. The multi-byte sequences produced and used by number conversion routines see Byte/Number Conversions are always big-endian.
read-bytes returns a newly allocated bytes-array filled with
(abs n) bytes read from port. If n is positive, then
the first byte read is stored at index 0; otherwise the last byte
read is stored at index 0. Note that the length of the returned
byte-array will be less than (abs n) if port reaches
end-of-file.
port may be omitted, in which case it defaults to the value returned
by current-input-port.
write-bytes writes (abs n) bytes to output-port port. If n is
positive, then the first byte written is index 0 of bytes; otherwise
the last byte written is index 0 of bytes. write-bytes returns an unspecified
value.
port may be omitted, in which case it defaults to the value returned
by current-output-port.
subbytes-read! and subbytes-write provide
lower-level procedures for reading and writing blocks of bytes. The
relative size of start and end determines the order of
writing.
Fills bts with up to (abs (- start end)) bytes
read from port. The first byte read is stored at index bts.
subbytes-read! returns the number of bytes read.
port may be omitted, in which case it defaults to the value returned
by current-input-port.
subbytes-write writes (abs (- start end)) bytes to
output-port port. The first byte written is index start of bts. subbytes-write
returns the number of bytes written.
port may be omitted, in which case it defaults to the value returned
by current-output-port.
Next: MAT-File Format, Previous: Byte, Up: Data Structures [Contents][Index]
(require 'byte-number)
The multi-byte sequences produced and used by numeric conversion
routines are always big-endian. Endianness can be changed during
reading and writing bytes using read-bytes and
write-bytes See read-bytes.
The sign of the length argument to bytes/integer conversion procedures determines the signedness of the number.
Converts the first (abs n) bytes of big-endian bytes array
to an integer. If n is negative then the integer coded by the
bytes are treated as two’s-complement (can be negative).
(bytes->integer (bytes 0 0 0 15) -4) ⇒ 15 (bytes->integer (bytes 0 0 0 15) 4) ⇒ 15 (bytes->integer (bytes 255 255 255 255) -4) ⇒ -1 (bytes->integer (bytes 255 255 255 255) 4) ⇒ 4294967295 (bytes->integer (bytes 128 0 0 0) -4) ⇒ -2147483648 (bytes->integer (bytes 128 0 0 0) 4) ⇒ 2147483648
Converts the integer n to a byte-array of (abs n)
bytes. If n and len are both negative, then the bytes in the
returned array are coded two’s-complement.
(bytes->list (integer->bytes 15 -4)) ⇒ (0 0 0 15) (bytes->list (integer->bytes 15 4)) ⇒ (0 0 0 15) (bytes->list (integer->bytes -1 -4)) ⇒ (255 255 255 255) (bytes->list (integer->bytes 4294967295 4)) ⇒ (255 255 255 255) (bytes->list (integer->bytes -2147483648 -4)) ⇒ (128 0 0 0) (bytes->list (integer->bytes 2147483648 4)) ⇒ (128 0 0 0)
bytes must be a 4-element byte-array. bytes->ieee-float calculates and returns the
value of bytes interpreted as a big-endian IEEE 4-byte (32-bit) number.
(bytes->ieee-float (bytes 0 0 0 0)) ⇒ 0.0 (bytes->ieee-float (bytes #x80 0 0 0)) ⇒ -0.0 (bytes->ieee-float (bytes #x40 0 0 0)) ⇒ 2.0 (bytes->ieee-float (bytes #x40 #xd0 0 0)) ⇒ 6.5 (bytes->ieee-float (bytes #xc0 #xd0 0 0)) ⇒ -6.5 (bytes->ieee-float (bytes 0 #x80 0 0)) ⇒ 11.754943508222875e-39 (bytes->ieee-float (bytes 0 #x40 0 0)) ⇒ 5.877471754111437e-39 (bytes->ieee-float (bytes 0 0 0 1)) ⇒ 1.401298464324817e-45 (bytes->ieee-float (bytes #xff #x80 0 0)) ⇒ -inf.0 (bytes->ieee-float (bytes #x7f #x80 0 0)) ⇒ +inf.0 (bytes->ieee-float (bytes #x7f #x80 0 1)) ⇒ 0/0 (bytes->ieee-float (bytes #x7f #xc0 0 0)) ⇒ 0/0
bytes must be a 8-element byte-array. bytes->ieee-double calculates and returns the
value of bytes interpreted as a big-endian IEEE 8-byte (64-bit) number.
(bytes->ieee-double (bytes 0 0 0 0 0 0 0 0)) ⇒ 0.0 (bytes->ieee-double (bytes #x80 0 0 0 0 0 0 0)) ⇒ -0.0 (bytes->ieee-double (bytes #x40 0 0 0 0 0 0 0)) ⇒ 2.0 (bytes->ieee-double (bytes #x40 #x1A 0 0 0 0 0 0)) ⇒ 6.5 (bytes->ieee-double (bytes #xC0 #x1A 0 0 0 0 0 0)) ⇒ -6.5 (bytes->ieee-double (bytes 0 8 0 0 0 0 0 0)) ⇒ 11.125369292536006e-309 (bytes->ieee-double (bytes 0 4 0 0 0 0 0 0)) ⇒ 5.562684646268003e-309 (bytes->ieee-double (bytes 0 0 0 0 0 0 0 1)) ⇒ 4.0e-324 (bytes->ieee-double (list->bytes '(127 239 255 255 255 255 255 255))) 179.76931348623157e306 (bytes->ieee-double (bytes #xFF #xF0 0 0 0 0 0 0)) ⇒ -inf.0 (bytes->ieee-double (bytes #x7F #xF0 0 0 0 0 0 0)) ⇒ +inf.0 (bytes->ieee-double (bytes #x7F #xF8 0 0 0 0 0 0)) ⇒ 0/0
Returns a 4-element byte-array encoding the IEEE single-precision floating-point of x.
(bytes->list (ieee-float->bytes 0.0)) ⇒ (0 0 0 0) (bytes->list (ieee-float->bytes -0.0)) ⇒ (128 0 0 0) (bytes->list (ieee-float->bytes 2.0)) ⇒ (64 0 0 0) (bytes->list (ieee-float->bytes 6.5)) ⇒ (64 208 0 0) (bytes->list (ieee-float->bytes -6.5)) ⇒ (192 208 0 0) (bytes->list (ieee-float->bytes 11.754943508222875e-39)) ⇒ ( 0 128 0 0) (bytes->list (ieee-float->bytes 5.877471754111438e-39)) ⇒ ( 0 64 0 0) (bytes->list (ieee-float->bytes 1.401298464324817e-45)) ⇒ ( 0 0 0 1) (bytes->list (ieee-float->bytes -inf.0)) ⇒ (255 128 0 0) (bytes->list (ieee-float->bytes +inf.0)) ⇒ (127 128 0 0) (bytes->list (ieee-float->bytes 0/0)) ⇒ (127 192 0 0)
Returns a 8-element byte-array encoding the IEEE double-precision floating-point of x.
(bytes->list (ieee-double->bytes 0.0)) ⇒ (0 0 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes -0.0)) ⇒ (128 0 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes 2.0)) ⇒ (64 0 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes 6.5)) ⇒ (64 26 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes -6.5)) ⇒ (192 26 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes 11.125369292536006e-309))
⇒ ( 0 8 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes 5.562684646268003e-309))
⇒ ( 0 4 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes 4.0e-324))
⇒ ( 0 0 0 0 0 0 0 1)
(bytes->list (ieee-double->bytes -inf.0)) ⇒ (255 240 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes +inf.0)) ⇒ (127 240 0 0 0 0 0 0)
(bytes->list (ieee-double->bytes 0/0)) ⇒ (127 248 0 0 0 0 0 0)
The string<? ordering of big-endian byte-array
representations of fixed and IEEE floating-point numbers agrees with
the numerical ordering only when those numbers are non-negative.
Straighforward modification of these formats can extend the byte-collating order to work for their entire ranges. This agreement enables the full range of numbers as keys in indexed-sequential-access-method databases.
Modifies sign bit of byte-vector so that string<? ordering of
two’s-complement byte-vectors matches numerical order. integer-byte-collate! returns
byte-vector and is its own functional inverse.
Returns copy of byte-vector with sign bit modified so that string<?
ordering of two’s-complement byte-vectors matches numerical order.
integer-byte-collate is its own functional inverse.
Modifies byte-vector so that string<? ordering of IEEE floating-point
byte-vectors matches numerical order. ieee-byte-collate! returns byte-vector.
Given byte-vector modified by ieee-byte-collate!, reverses the byte-vector
modifications.
Returns copy of byte-vector encoded so that string<? ordering of IEEE
floating-point byte-vectors matches numerical order.
Given byte-vector returned by ieee-byte-collate, reverses the byte-vector
modifications.
Next: Portable Image Files, Previous: Byte/Number Conversions, Up: Data Structures [Contents][Index]
(require 'matfile)
http://www.mathworks.com/access/helpdesk/help/pdf_doc/matlab/matfile_format.pdf
This package reads MAT-File Format version 4 (MATLAB) binary data files. MAT-files written from big-endian or little-endian computers having IEEE format numbers are currently supported. Support for files written from VAX or Cray machines could also be added.
The numeric and text matrix types handled; support for sparse matrices awaits a sample file.
filename should be a string naming an existing file containing a
MATLAB Version 4 MAT-File. The matfile:read procedure reads matrices from the
file and returns a list of the results; a list of the name string and
array for each matrix.
filename should be a string naming an existing file containing a
MATLAB Version 4 MAT-File. The matfile:load procedure reads matrices from the
file and defines the string-ci->symbol for each matrix to its
corresponding array. matfile:load returns a list of the symbols defined.
Next: Collections, Previous: MAT-File Format, Up: Data Structures [Contents][Index]
(require 'pnm)
The string path must name a portable bitmap graphics file.
pnm:type-dimensions returns a list of 4 items:
The current set of file-type symbols is:
Reads the portable bitmap graphics file named by path into array. array must be the correct size and type for path. array is returned.
pnm:image-file->array creates and returns an array with the
portable bitmap graphics file named by path read into it.
Writes the contents of array to a type image file named path. The file will have pixel values between 0 and maxval, which must be compatible with type. For ‘pbm’ files, maxval must be ‘1’. comments are included in the file header.
Next: Dynamic Data Type, Previous: Portable Image Files, Up: Data Structures [Contents][Index]
(require 'collect)
Routines for managing collections. Collections are aggregate data structures supporting iteration over their elements, similar to the Dylan(TM) language, but with a different interface. They have elements indexed by corresponding keys, although the keys may be implicit (as with lists).
New types of collections may be defined as YASOS objects (see Yasos). They must support the following operations:
(collection? self) (always returns #t);
(size self) returns the number of elements in the collection;
(print self port) is a specialized print operation
for the collection which prints a suitable representation on the given
port or returns it as a string if port is #t;
(gen-elts self) returns a thunk which on successive
invocations yields elements of self in order or gives an error if
it is invoked more than (size self) times;
(gen-keys self) is like gen-elts, but yields the
collection’s keys in order.
They might support specialized for-each-key and
for-each-elt operations.
A predicate, true initially of lists, vectors and strings. New sorts of
collections must answer #t to collection?.
proc is a procedure taking as many arguments as there are
collections (at least one). The collections are iterated
over in their natural order and proc is applied to the elements
yielded by each iteration in turn. The order in which the arguments are
supplied corresponds to te order in which the collections appear.
do-elts is used when only side-effects of proc are of
interest and its return value is unspecified. map-elts returns a
collection (actually a vector) of the results of the applications of
proc.
Example:
(map-elts + (list 1 2 3) (vector 1 2 3)) ⇒ #(2 4 6)
These are analogous to map-elts and do-elts, but each
iteration is over the collections’ keys rather than their
elements.
Example:
(map-keys + (list 1 2 3) (vector 1 2 3)) ⇒ #(0 2 4)
These are like do-keys and do-elts but only for a single
collection; they are potentially more efficient.
A generalization of the list-based reduce-init
(see Lists as sequences) to collections.
Examples:
(reduce + 0 (vector 1 2 3)) ⇒ 6 (reduce union '() '((a b c) (b c d) (d a))) ⇒ (c b d a).
Reduce called with two arguments will work as does the
procedure of the same name from See Common List Functions.
A generalization of the list-based some
(see Lists as sequences) to collections.
Example:
(any? odd? (list 2 3 4 5)) ⇒ #t
A generalization of the list-based every
(see Lists as sequences) to collections.
Example:
(every? collection? '((1 2) #(1 2))) ⇒ #t
Returns #t iff there are no elements in collection.
(empty? collection) ≡ (zero? (size collection))
Returns the number of elements in collection.
See Setters for a definition of setter. N.B.
(setter list-ref) doesn’t work properly for element 0 of a
list.
Here is a sample collection: simple-table which is also a
table.
(define-predicate TABLE?)
(define-operation (LOOKUP table key failure-object))
(define-operation (ASSOCIATE! table key value)) ;; returns key
(define-operation (REMOVE! table key)) ;; returns value
(define (MAKE-SIMPLE-TABLE)
(let ( (table (list)) )
(object
;; table behaviors
((TABLE? self) #t)
((SIZE self) (size table))
((PRINT self port) (format port "#<SIMPLE-TABLE>"))
((LOOKUP self key failure-object)
(cond
((assq key table) => cdr)
(else failure-object)
))
((ASSOCIATE! self key value)
(cond
((assq key table)
=> (lambda (bucket) (set-cdr! bucket value) key))
(else
(set! table (cons (cons key value) table))
key)
))
((REMOVE! self key);; returns old value
(cond
((null? table) (slib:error "TABLE:REMOVE! Key not found: " key))
((eq? key (caar table))
(let ( (value (cdar table)) )
(set! table (cdr table))
value)
)
(else
(let loop ( (last table) (this (cdr table)) )
(cond
((null? this)
(slib:error "TABLE:REMOVE! Key not found: " key))
((eq? key (caar this))
(let ( (value (cdar this)) )
(set-cdr! last (cdr this))
value)
)
(else
(loop (cdr last) (cdr this)))
) ) )
))
;; collection behaviors
((COLLECTION? self) #t)
((GEN-KEYS self) (collect:list-gen-elts (map car table)))
((GEN-ELTS self) (collect:list-gen-elts (map cdr table)))
((FOR-EACH-KEY self proc)
(for-each (lambda (bucket) (proc (car bucket))) table)
)
((FOR-EACH-ELT self proc)
(for-each (lambda (bucket) (proc (cdr bucket))) table)
) ) ) )
Next: Hash Tables, Previous: Collections, Up: Data Structures [Contents][Index]
(require 'dynamic)
Create and returns a new dynamic whose global value is obj.
Returns true if and only if obj is a dynamic. No object
satisfying dynamic? satisfies any of the other standard type
predicates.
Return the value of the given dynamic in the current dynamic environment.
Change the value of the given dynamic to obj in the current dynamic environment. The returned value is unspecified.
Invoke and return the value of the given thunk in a new, nested dynamic environment in which the given dynamic has been bound to a new location whose initial contents are the value obj. This dynamic environment has precisely the same extent as the invocation of the thunk and is thus captured by continuations created within that invocation and re-established by those continuations when they are invoked.
The dynamic-bind macro is not implemented.
Next: Macroless Object System, Previous: Dynamic Data Type, Up: Data Structures [Contents][Index]
(require 'hash-table)
Returns a hash function (like hashq, hashv, or
hash) corresponding to the equality predicate pred.
pred should be eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or
string-ci=?.
A hash table is a vector of association lists.
Returns a vector of k empty (association) lists.
Hash table functions provide utilities for an associative database.
These functions take an equality predicate, pred, as an argument.
pred should be eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or
string-ci=?.
Returns a hash association function of 2 arguments, key and
hashtab, corresponding to pred. The returned function
returns a key-value pair whose key is pred-equal to its first
argument or #f if no key in hashtab is pred-equal to
the first argument.
Returns a procedure of 2 arguments, hashtab and key, which
returns the value associated with key in hashtab or
#f if key does not appear in hashtab.
Returns a procedure of 3 arguments, hashtab, key, and value, which modifies hashtab so that key and value associated. Any previous value associated with key will be lost.
Returns a procedure of 2 arguments, hashtab and key, which modifies hashtab so that the association whose key is key is removed.
Returns a new hash table formed by mapping proc over the keys and values of hash-table. proc must be a function of 2 arguments which returns the new value part.
Applies proc to each pair of keys and values of hash-table. proc must be a function of 2 arguments. The returned value is unspecified.
hash-rehasher accepts a hash table predicate and returns a function of two
arguments hashtab and new-k which is specialized for
that predicate.
This function is used for nondestrutively resizing a hash table. hashtab should be an existing hash-table using pred, new-k is the size of a new hash table to be returned. The new hash table will have all of the associations of the old hash table.
Next: Priority Queues, Previous: Hash Tables, Up: Data Structures [Contents][Index]
(require 'object)
This is the Macroless Object System written by Wade Humeniuk (whumeniu@datap.ca). Conceptual Tributes: Yasos, MacScheme’s %object, CLOS, Lack of R4RS macros.
An object is an ordered association-list (by eq?) of methods
(procedures). Methods can be added (make-method!), deleted
(unmake-method!) and retrieved (get-method). Objects may
inherit methods from other objects. The object binds to the environment
it was created in, allowing closures to be used to hide private
procedures and data.
A generic-method associates (in terms of eq?) object’s method.
This allows scheme function style to be used for objects. The calling
scheme for using a generic method is (generic-method object param1
param2 ...).
A method is a procedure that exists in the object. To use a method get-method must be called to look-up the method. Generic methods implement the get-method functionality. Methods may be added to an object associated with any scheme obj in terms of eq?
A generic method that returns a boolean value for any scheme obj.
A object’s method asscociated with a generic-predicate. Returns
#t.
Returns an object. Current object implementation is a tagged vector.
ancestors are optional and must be objects in terms of object?.
ancestors methods are included in the object. Multiple
ancestors might associate the same generic-method with a method.
In this case the method of the ancestor first appearing in the
list is the one returned by get-method.
Returns boolean value whether obj was created by make-object.
Returns a procedure which be associated with an object’s methods. If exception-procedure is specified then it is used to process non-objects.
Returns a boolean procedure for any scheme object.
Associates method to the generic-method in the object. The
method overrides any previous association with the
generic-method within the object. Using unmake-method!
will restore the object’s previous association with the
generic-method. method must be a procedure.
Makes a predicate method associated with the generic-predicate.
Removes an object’s association with a generic-method .
Returns the object’s method associated (if any) with the generic-method. If no associated method exists an error is flagged.
(require 'object)
(define instantiate (make-generic-method))
(define (make-instance-object . ancestors)
(define self (apply make-object
(map (lambda (obj) (instantiate obj)) ancestors)))
(make-method! self instantiate (lambda (self) self))
self)
(define who (make-generic-method))
(define imigrate! (make-generic-method))
(define emigrate! (make-generic-method))
(define describe (make-generic-method))
(define name (make-generic-method))
(define address (make-generic-method))
(define members (make-generic-method))
(define society
(let ()
(define self (make-instance-object))
(define population '())
(make-method! self imigrate!
(lambda (new-person)
(if (not (eq? new-person self))
(set! population (cons new-person population)))))
(make-method! self emigrate!
(lambda (person)
(if (not (eq? person self))
(set! population
(comlist:remove-if (lambda (member)
(eq? member person))
population)))))
(make-method! self describe
(lambda (self)
(map (lambda (person) (describe person)) population)))
(make-method! self who
(lambda (self) (map (lambda (person) (name person))
population)))
(make-method! self members (lambda (self) population))
self))
(define (make-person %name %address)
(define self (make-instance-object society))
(make-method! self name (lambda (self) %name))
(make-method! self address (lambda (self) %address))
(make-method! self who (lambda (self) (name self)))
(make-method! self instantiate
(lambda (self)
(make-person (string-append (name self) "-son-of")
%address)))
(make-method! self describe
(lambda (self) (list (name self) (address self))))
(imigrate! self)
self)
Inheritance:
<inverter>::(<number> <description>)
Generic-methods
<inverter>::value ⇒ <number>::value
<inverter>::set-value! ⇒ <number>::set-value!
<inverter>::describe ⇒ <description>::describe
<inverter>::help
<inverter>::invert
<inverter>::inverter?
Inheritance
<number>::()
Slots
<number>::<x>
Generic Methods
<number>::value
<number>::set-value!
(require 'object)
(define value (make-generic-method (lambda (val) val)))
(define set-value! (make-generic-method))
(define invert (make-generic-method
(lambda (val)
(if (number? val)
(/ 1 val)
(error "Method not supported:" val)))))
(define noop (make-generic-method))
(define inverter? (make-generic-predicate))
(define describe (make-generic-method))
(define help (make-generic-method))
(define (make-number x)
(define self (make-object))
(make-method! self value (lambda (this) x))
(make-method! self set-value!
(lambda (this new-value) (set! x new-value)))
self)
(define (make-description str)
(define self (make-object))
(make-method! self describe (lambda (this) str))
(make-method! self help (lambda (this) "Help not available"))
self)
(define (make-inverter)
(let* ((self (make-object
(make-number 1)
(make-description "A number which can be inverted")))
(<value> (get-method self value)))
(make-method! self invert (lambda (self) (/ 1 (<value> self))))
(make-predicate! self inverter?)
(unmake-method! self help)
(make-method! self help
(lambda (self)
(display "Inverter Methods:") (newline)
(display " (value inverter) ==> n") (newline)))
self))
;;;; Try it out
(define invert! (make-generic-method))
(define x (make-inverter))
(make-method! x invert! (lambda (x) (set-value! x (/ 1 (value x)))))
(value x) ⇒ 1
(set-value! x 33) ⇒ undefined
(invert! x) ⇒ undefined
(value x) ⇒ 1/33
(unmake-method! x invert!) ⇒ undefined
(invert! x) error→ ERROR: Method not supported: x
Next: Queues, Previous: Macroless Object System, Up: Data Structures [Contents][Index]
(require 'priority-queue)
This algorithm for priority queues is due to Introduction to Algorithms by T. Cormen, C. Leiserson, R. Rivest. 1989 MIT Press.
Returns a binary heap suitable which can be used for priority queue operations.
Returns the number of elements in heap.
Inserts item into heap. item can be inserted multiple times. The value returned is unspecified.
Returns the item which is larger than all others according to the
pred<? argument to make-heap. If there are no items in
heap, an error is signaled.
Next: Records, Previous: Priority Queues, Up: Data Structures [Contents][Index]
(require 'queue)
A queue is a list where elements can be added to both the front and rear, and removed from the front (i.e., they are what are often called dequeues). A queue may also be used like a stack.
Returns a new, empty queue.
Returns #t if obj is a queue.
Returns #t if the queue q is empty.
Adds datum to the front of queue q.
Adds datum to the rear of queue q.
Both of these procedures remove and return the datum at the front of
the queue. queue-pop! is used to suggest that the queue is
being used like a stack.
All of the following functions raise an error if the queue q is empty.
Removes and returns (the list) of all contents of queue q.
Returns the datum at the front of the queue q.
Returns the datum at the rear of the queue q.
Previous: Queues, Up: Data Structures [Contents][Index]
(require 'record)
The Record package provides a facility for user to define their own record data types.
Returns a record-type descriptor, a value representing a new data type disjoint from all others. The type-name argument must be a string, but is only used for debugging purposes (such as the printed representation of a record of the new type). The field-names argument is a list of symbols naming the fields of a record of the new type. It is an error if the list contains any duplicates. It is unspecified how record-type descriptors are represented.
Returns a procedure for constructing new members of the type represented
by rtd. The returned procedure accepts exactly as many arguments
as there are symbols in the given list, field-names; these are
used, in order, as the initial values of those fields in a new record,
which is returned by the constructor procedure. The values of any
fields not named in that list are unspecified. The field-names
argument defaults to the list of field names in the call to
make-record-type that created the type represented by rtd;
if the field-names argument is provided, it is an error if it
contains any duplicates or any symbols not in the default list.
Returns a procedure for testing membership in the type represented by rtd. The returned procedure accepts exactly one argument and returns a true value if the argument is a member of the indicated record type; it returns a false value otherwise.
Returns a procedure for reading the value of a particular field of a
member of the type represented by rtd. The returned procedure
accepts exactly one argument which must be a record of the appropriate
type; it returns the current value of the field named by the symbol
field-name in that record. The symbol field-name must be a
member of the list of field-names in the call to make-record-type
that created the type represented by rtd.
Returns a procedure for writing the value of a particular field of a
member of the type represented by rtd. The returned procedure
accepts exactly two arguments: first, a record of the appropriate type,
and second, an arbitrary Scheme value; it modifies the field named by
the symbol field-name in that record to contain the given value.
The returned value of the modifier procedure is unspecified. The symbol
field-name must be a member of the list of field-names in the call
to make-record-type that created the type represented by
rtd.
In May of 1996, as a product of discussion on the rrrs-authors
mailing list, I rewrote record.scm to portably implement type
disjointness for record data types.
As long as an implementation’s procedures are opaque and the
record code is loaded before other programs, this will give
disjoint record types which are unforgeable and incorruptible by R4RS
procedures.
As a consequence, the procedures record?,
record-type-descriptor, record-type-name.and
record-type-field-names are no longer supported.
Next: Sorting and Searching, Previous: Other Packages, Up: Other Packages [Contents][Index]