Using the C++ Math Library

Representing Input Arguments As a Cell Array

In MATLAB you can substitute a cell array for a comma-separated list of MATLAB variables when you pass input arguments to a function. MATLAB treats the contents of each cell as a separate input argument. To trigger this functionality, you specify multiple values by indexing into the cell array with, for example, the colon index or a vector index.

For example, the MATLAB expression

T{1:5}

when passed as an input argument is equivalent to a comma-separated list of the contents of the first five cells of T. Simply passing the cell array T produces an error.

The MATLAB C++ Math Library also supports the expansion of the contents of a cell array into separate input arguments for library functions. For functions that implement MATLAB varargin functions, you use mwArray::cell to obtain an array reference that returns multiple values.

For example, given the varargin function

void varargin_func(mwArray a, mwArray b,
                   const mwVarargin &varargin
                   const mwArray v1=mwArray::DIN, ...,
                  .
                  .
                  .
                   const mwArray &v32=mwArray::DIN);

you can make the following call:

varargin_func(A, B, C.cell(colon(1,5)));

A and B, existing mwArrays, are passed as explicit arguments. C is a cell array that contains at least five cells. The embedded call to cell() uses the index {1:5} to return multiple values: the first five cells of C. The MATLAB C++ Math Library passes these as individual arguments to varargin_func().

Location of the Indexed Cell Array in the Argument List

• Pass the return from the cell array indexing operation as one of the variable-length arguments in the input argument list. That reference identifies multiple arrays.
• Do not pass the return from a cell array indexing operation as an explicit argument.

For example, you cannot make this call to the example varargin function.

varargin_func(C.cell(1,5), A, B);

Given the definition of varargin_func(), the first argument position is reserved for an explicit, single argument. The MATLAB C++ Math Library does not handle multiple values in an explicit position.

• You can pass other array arguments or other cell array indexing expressions before or after a cell array indexing expression, all in a varargin argument position.

See Indexing into Cell Arrays in Chapter 4 to learn more about indexing into cell arrays.

Example Program: Passing Functions As Arguments (ex3.cpp)

Using the Mathematical Operators