Whether the function is higher-order: it takes a function argument, may return one, or calls one of its own formals as a function. function(x) x alone is not higher-order.
function(x) x
FunctionSemantics.isHigherOrder
Whether the function is higher-order: it takes a function argument, may return one, or calls one of its own formals as a function.
function(x) xalone is not higher-order.