Perhaps this will help you understand why your question is idiotic:
EDIT:
So your answer is *no*, since according to your used definition of a function, ordered pairs of the form (x,y) are involved, such that x or y are always place holders of something (as done by René Descartes).
By being limited to such definition of a function, which claims that a function is some ordered pair of Cartesian product (as done by René Descartes), there is no wonder that a case like (x,) seems to be idiotic.
But you see jsfisher, in this
philosophical forum we do not deal only with the current agreements among mathematicians about mathematical subjects, but we also deal with the ability to expand given mathematical subjects beyond thier current understanding and use (where in this case the discussed subject is the definition of a function), where the expansion is done from within (by mutation) when new insights of the discussed mathematical subjects are involved.
All along this
philosophical thread you claim that definitions are not subjects for changing, and this claim is not a mathematical claim, but it is a philosophical claim.
It seems that you do not understand that your claims, in this case, are philosophical claims.
Let us use some analogy, in order to address better the above.
According to the Geocentric model the Earth is positioned in the center of orbits, where these orbits have shapes of perfect circles.
According to the current Heliocentric model, the sun is positioned in a given center of several elliptic orbits around it.
According to jsfisher's philosophy, concepts like
center or
orbit need new definitions, because these concepts are already "well-defined" by the Geocentric model.
But as you see, physicists use concepts like
center or
orbit in both models without giving them new definitions, but they give them new interpretations, which enable to conclude that the Geocentric model is wrong (end this conclusion is possible in the first place exactly because no new definitions to concepts like
center or
orbit, are given in the current Heliocentric model.)
The demand of "pure" mathematicians to provide new definition to any change, establish mathematical environment of isolated context-dependent-only "worlds", which easily enable to miss new insights about possible discussed subjects, and in this case, a function without any output at all (it returns nothing).