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## C++ Question

**From**: |
Quentin H. Spencer |

**Subject**: |
C++ Question |

**Date**: |
Mon, 31 Mar 2003 11:58:50 -0700 |

**User-agent**: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3) Gecko/20030314 |

Hello all,

`I have been writing some functions in C that use the octave ComplexSVD
``class, and I'm having trouble understanding some strange behavior.
``Initially I wrote the function with the following syntax:
`
ComplexSVD svd;
svd = ComplexSVD( matrix , SVD::std);
ComplexMatrix U = svd.left_singular_matrix();

`Later I changed the syntax to the following (which mirrors the syntax
``used in svd.cc).
`
ComplexSVD svd( matrix , SVD::std);
ComplexMatrix U = svd.left_singular_matrix();

`When using the first syntax, the function would usually return properly
``the first time, but subsequent runnings of my C++ function (and
``sometimes even octave's builtin svd function) often resulted in the
``following:
`
error: ComplexSVD: U not computed because type == SVD::sigma_only

`This is usally followed by a segmentation fault. There could be some
``technicality about C++ that I don't understand here, but I don't see the
``different between these two implementations. Can anyone enlighten me?
`
Quentin Spencer
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**C++ Question**,
*Quentin H. Spencer* **<=**