-------------------------------------------
functs,vars (left-click): to write computed fieldsign
  set fs <$hemi.fs>
  write_fieldsign
  set fm <$hemi.fm>
  write_fsmask
-------------------------------------------

The "W" button on the "fs:" entry line writes out
current fieldsign and fieldsign mask (generated
by function: compute_fieldsign, after reading
eccen and polar data -- see fs-make.tcl) as files
$fs and $fm.

The fieldsign name, $fs, is the current value of
the "fs:" entry at the left.  The tcl interface
auto-generates the fieldsign mask output file by
stripping the .fs suffix and replacing it with
an .fm suffix.
