sylv Sylvester equation.

## Syntax

    sylv(A, B, C, flag)

## Arguments

A,B,C

  three real matrices of appropriate dimensions.

flag

  character string (`'c'` or `'d'`)

## Description

`X= sylv(A, B, C, 'c')` computes `X`, solution of the "continuous time" Sylvester equation

    A*X+X*B = C

`X=sylv(A, B, C, 'd')` computes `X`, solution of the modified "discrete time" Sylvester equation

    A*X*B+X = C

`X=-sylv(-A, B, C, 'd')` computes `X`, solution of the real "discrete time" Sylvester equation

    A*X*B-X = C

## Examples

    // Continuous time Sylvester equation:
    A = rand(4, 4); C = rand(4, 3); B = rand(3, 3);
    X = sylv(A, B, C, 'c');
    norm(A*X+X*B-C)

    // Modified Discrete time Sylvester equation:
    X = sylv(A, B, C, 'd');
    norm(A*X*B+X-C)

    // Real Discrete time Sylvester equation:
    X = -sylv(-A, B, C, 'd');
    norm(A*X*B-X-C)

## See also

- lyap