for k being Nat
for A being QC-alphabet
for V being non empty Subset of (QC-variables A)
for P being QC-pred_symbol of k,A
for l being QC-variable_list of k,A holds
( Vars ((P ! l),V) = variables_in (l,V) & Vars ((P ! l),V) = { (l . i) where i is Nat : ( 1 <= i & i <= len l & l . i in V ) } )