seq2multislice

Convert a multidimensional subsequence string to a MultiSlice object.

Installation

npm install @stdlib/slice-base-seq2multislice

Usage

var seq2multislice = require( '@stdlib/slice-base-seq2multislice' );

seq2multislice( str, shape, strict )

Converts a multidimensional subsequence string to a MultiSlice object, where shape specifies the maximum allowed slice shape.

var s = seq2multislice( ':5', [ 10 ], false );
// returns <MultiSlice>

var s0 = s.data[ 0 ];
// returns <Slice>

var v = s0.start;
// returns 0

v = s0.stop;
// returns 5

v = s0.step;
// returns 1

A multidimensional subsequence string is a comma-separated list of single-dimension indexing expressions (i.e., integers and/or subsequence strings). For example, the following

2
:
2:
:10
2:10
::-1
10:2:-1
:2:
2:10:
2::2
:10:2
:, :, :
1, 2, 3
0:10, 1:20:2, ::-1
...
:, ..., 2

are all valid multidimensional subsequence strings. The function returns an error object if provided an invalid subsequence string.

var s = seq2multislice( '1:2:3:4', [ 10 ], false );
// returns { 'code': 'ERR_SLICE_INVALID_SUBSEQUENCE' }

When strict is true, the function returns an error object if a subsequence string resolves to a slice exceeding index bounds.

var s = seq2multislice( '10:20', [ 10 ], true );
// returns { 'code': 'ERR_SLICE_OUT_OF_BOUNDS' }

A returned error object may have one of the following error codes:

• ERR_SLICE_INVALID_SUBSEQUENCE: a subsequence string is invalid.
• ERR_SLICE_INVALID_INCREMENT: a subsequence string must have a non-zero increment.
• ERR_SLICE_OUT_OF_BOUNDS: a subsequence string resolves to a slice exceeding index bounds.
• ERR_SLICE_TOO_MANY_DIMENSIONS: a subsequence string has more dimensions than the provided shape.
• ERR_SLICE_INSUFFICIENT_DIMENSIONS: a subsequence string has too few dimensions.
• ERR_SLICE_INVALID_ELLIPSIS: a subsequence string must only contain at most one ellipsis.

Notes

• Providing a single nonnegative integer i as a single-dimension index indexes the same elements as the subsequence i:i+1.
• Providing a single negative integer i as a single-dimension index indexes the same elements as the subsequence n+i:n+i+i, where n is the dimension size.
• While integers index the same elements as equivalent subsequences, providing an integer as a single-dimension index indicates to reduce the number of dimensions by one (e.g., if the provided shape corresponds to an array having rank 2, then rank(A)-1 == rank(A['0,:'])). In contrast, providing a subsequence indicates to retain a respective dimension (e.g., if the provided shape corresponds to an array having rank 2, then rank(A) == rank(A[':,:'])).
• A multidimensional subsequence string can only contain one ellipsis ('...') operator. An ellipsis indicates to apply : to each dimension necessary to index all dimensions (e.g., if A has rank 4, A['1:, ..., 2:5'] == A['1:, :, :, 2:5']).
• Except in the case of providing a single ellipsis, the number of single-dimension indexing expressions must equal the number of dimensions in the input shape.

Examples

var seq2multislice = require( '@stdlib/slice-base-seq2multislice' );

var s = seq2multislice( ':,:,:', [ 10, 10, 10 ], false );
var d = s.data;
// returns [ <Slice>, <Slice>, <Slice> ]

s = seq2multislice( '3,2:10,:', [ 10, 10, 10 ], false );
d = s.data;
// returns [ 3, <Slice>, <Slice> ]

s = seq2multislice( '2,2:,-5', [ 10, 10, 10 ], false );
d = s.data;
// returns [ 2, <Slice>, -5 ]

s = seq2multislice( '::-2,-1,...,:', [ 10, 10, 10, 10, 10, 10 ], false );
d = s.data;
// returns [ <Slice>, -1, <Slice>, <Slice>, <Slice>, <Slice> ]

s = seq2multislice( 'foo,bar', [ 10, 10 ], false );
// returns { 'code': 'ERR_SLICE_INVALID_SUBSEQUENCE' }

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.