• ← MemberQ
• → SubsetQ

NotListQ

NotListQ[expr]

returns True if expr is not a list. This function is primarily used in function patterns for specifying type of a parameter.

Consider this definition for taking the deriviate Sin of a function:

• • MyD[Sin[f_],x_?NotListQ] := D[f,x]*Cos[f]

=

We use “MyD” above to distinguish it from the Builtin D. Now let's try it:

• • MyD[Sin[2 x], x]

And compare it with the Builtin deriviative function D:

• • D[Sin[2 x], x]

Note however the pattern only matches if the x parameter is not a list:

• • MyD[{Sin[2], Sin[4]}, {1, 2}]