definedfields - return index of list's defined fields
If l is a list tlist mlist k=definedfields(l) returns in k the indices of the defined list fields. This function is useful because indexing undefined fields produces an error.
l=list(1);l(3)=5 k=definedfields(l) t=tlist('x');t(5)=4 definedfields(t) m=mlist(['m','a','b']);m.b='sdfgfgd' definedfields(m)
list , tlist , mlist , insertion , extraction ,