Re: [TCL] Strange behavior, or so I think, for package require

Andrew Falanga wrote:
> Why does that first call to package require seem to "include" virtually
> all possible packages in the auto_path variable?

First, note that [package names] does *not* return all packages
that are "present" in the interp. It returns names of all packages
that Tcl knows how to make present in the interp.

Try [package unknown] in your interpreter. It will return
tclPkgUnknown. That indicates it is the [tclPkgUnknown] command
that is registered to find installed packages. This is the default.

Why does [tclPkgUnknown] go find all packages when it goes looking
for just one? Because that's how it was written. The design intent
is lost to history, best I can tell, but this has been the default
behavior of Tcl as long as the [package] command has existed, so
I'm surprised that you are surprised by it.

If you wish, you can use [package unknown] to register a different
package finding command that operates more to your liking, but
you may run into compatibility issues with packages that assume
the default finder when performing their install.

-- 
| Don Porter          Mathematical and Computational Sciences Division |
| donald.porter@nist.gov             Information Technology Laboratory |
| http://math.nist.gov/~DPorter/                                  NIST |
|______________________________________________________________________|