tclforces: measure distances in NAMD 2.6b2 ?

From: Sebastian Stolzenberg (
Date: Sat Jul 24 2010 - 21:46:51 CDT

Dear All,

I am bound to use NAMD version 2.6b2.

For a tclforcescript, could anybody kindly tell me
how I can measure a distance between two atoms?

Unfortunately, the functions:
as described in the VMD tutorial don't work, though they work in
different NAMD versions.
FATAL ERROR: Setting parameter veclength2 from script failed!

[expr sqrt (2)]
seems to work, yet I am afraid using [expr sqrt( sum(...)) may slow
things down.

Are there alternative functions I can use?

Thank You so much,


these are the commands I use in the tclforcescript:
set dist [veclength2 $distvec]
#set dist [vecdist $distvec [vecsub $distvec $distvec ]]

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