R help - Jan 2007 - has anyone implemented LARS with the "positive lasso"?

Hi,
I am interested in a modification to LARS that allows for positive-only
constraints in the variables (with details about how to implement this as
described in section 3.4 of the Efron et al (2003) LARS paper).

Before I dive into the "lars" package code myself, I was wondering if
anyone
knew of a version where this is available, or if another package that I have
not found can do this?

Thanks very much for any pointers.

-David

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