Construction of Cell matrices

In Quasar, it is possible to construct cell vectors/matrices, similar to in MATLAB:

A = `1,2,3j,zeros(4,4)´

(Matlab-syntax uses braces as in {1,2,3j,zeros(4,4)}).

Now, I have found that there are two problems with the cell construction syntax:

• The prime (´) cannot be represented with the ANSI character set and requires UTF-8 encoding. In the Redshift code editor, UTF-8 is used by default, however when editing Quasar code with other editors, problems can occur.
• The prime (´) is not present on QUERTY keyboards (in contrast to Belgian AZERTY keyboard). I suspect this is one of the reasons that the cell construction syntax is used rarely.
• Even the documentation system has problems with the prime symbol, that may be the cause that you cannot see it right now. In other words, it is an evil symbol and all evil should be extinct.

To solve these problems, the Quasar parser now also accepts an apostrophe ' (ASCII character 39, or in hex 27h) for closing:

A = `1,2,3j,zeros(4,4)'

Because the apostrophe character exists in ANSI and on QUERTY keyboards, the use of cell matrices constructions is greatly simplified.

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Note: the old-fashioned alternative was to construct cell matrices using the function cell, or vec[vec], vec[mat], vec[cube], … For example:

A = cell(4)
A[0] = 1j
A[1] = 2j
A[2] = 3j
A[3] = 4j

Note that this notation is not very elegant, compared to A='1j,2j,3j,4j'. Also it does not allow the compiler to fully determine the type of A (the compiler will find type(A) == "vec[??]" rather than type(A) == "cvec"). In the following section, we will discuss the type inference in more detail.

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Type inference

Another new feature of the compiler is that it attempts to infer the type from cell matrices. In earlier versions, all cell matrices defined with the above syntax, had type vec[??]. Now, this has changed, as illustrated by the following example:

    a = `[1, 2],[1, 2, 3]'
    print type(a)            % Prints vec[vec[int]]

    b = `(x->2*x), (x->3*x), (x->4*x)'
    print type(b)            % Prints [ [??->??] ]

    c = ` `[1, 2],[1,2]',`[1, 2, 3],[4, 5, 6]' '
    print type(c)            % Prints vec[vec[vec[int]]]

    d = ` [ [2, 1], [1, 2] ], [ [4, 3], [3, 4] ]'
    print type(d)            % Prints vec[mat]

    e = `(x:int->2*x), (x:int->3*x), (x:int->4*x)'
    print type(e)            % Prints vec[ [int->int] ]

This allows cell matrices that are constructed with the above syntax to be used from kernel functions. A simple example:

    d = `eye(4), ones(4,4)'

    parallel_do(size(d[0]), d, 
        __kernel__ (d : vec[mat], pos : ivec2) -> d[0][pos] += d[1][pos])
    print d[0]

The output is:

       [ [2,1,1,1],
         [1,2,1,1],
         [1,1,2,1],
         [1,1,1,2] ]