type(x,nothing) returns false for any valid Maple expression, except an expression sequence.

Expression sequences return an error, because each element would be interpreted as a separate argument to type.

Note that one use of this type is for a local variable declaration in a procedure, and indicates that the local is to be used as-is (e.g. in an internally constructed polynomial, or as a temporary placeholder), and will not be assigned. This is helpful to avoid mint warnings for variables that are used but not assigned.

$\mathrm{type}\left(5^{\frac{1}{2}}\,\mathrm{nothing}\right)$

$\mathrm{false}$

$\mathrm{type}\left(\frac{\sin \left(3x\right)}{\mathrm{\pi }}\,\mathrm{nothing}\right)$

$\mathrm{false}$

f := proc(n::posint, i::nonnegint) local pol, x::nothing; pol := expand((x+1)^n); return coeff(pol,x,i); end proc: