Matrix Object Interactions

The Matrix class implements the following python object interactions.

Intelligent string representation

Calling str(matrix) returns a string representation of the matrix.

• The element with the longest string representation in a column determines that column’s width.
• All elements are centered in their columns
• No matter how much the matrix and it’s elements change, the string is smartly adjusted to give the best representation.
• Calling print(matrix) simply writes this string representation to STDOUT.

Subscription

Note:

• Both rows and Columns are 1-indexed i.e indexing starts from 1.
• A slice always includes the stop index.

A subscription can be performed on a matrix to get:

1. The element at the given coordinate, if the subscript is a tuple of integers (row, col).
   • e.g matrix[1, 2]
   • Indices less than 1 are not allowed.
2. a new Matrix instance, the intersection of the selected rows and columns (called a “block-slice”), if the subscript is a tuple of slices.
   • e.g matrix[::2, 3:4]
   • the first slice selects rows.
   • the second slice selects columns.
   • any ‘stop’ greater than the number of rows/columns is “forgiven”.
   • Indices or steps less than 1 are not allowed.

These forms of subscription can also be used in an assignment to replace the element or block-slice.

• The value assigned to an element subscription must be a real number.
• While that assigned to a block-slice must be a 2D array (iterable of iterables) of real numbers of the same dimension as the matrix that would normally be returned by the block-slice.

They also support augmented assignments, as supported by the object returned by the form of subscription.

Truth-value Testing

A matrix has a truth values of False is it’s a null matrix, and True otherwise.

• This property can be used in truth-value testing.

Membership test for elements

A matrix can be tested if it contains a certain element.

Iteration over elements

Iterating over a matrix instance yields it’s elements in order starting from the first row.

• iter(matrix) returns a generator-iterator.
• It raises a RuntimeError if the matrix is resized during iteration.
• The generator also has an advanced usage. Itcan be set to any vaild row and column of the matrix from which to continue iteration using its send() method.
  • It accepts two forms of arguments:
    • An integer, continues yielding fom the start of the specified row.
    • a tuple (row, col) of integers; the row and column of the next element to yield.
    • The generator raises a StopIteration and closes if given any other type of argument.
  • The send() method returns the element at the specified position, so the next value yielded will be the next element.
  • The generator raises a StopIteration and closes if any given index is out of range.

Per-element rounding

This can be done in two ways:

• Calling round() on Matrix instances returns a new instance with each element rounded as though it were called on each element directly.
• Instance method round([ndigits]) rounds the matrix In-place.