Maybe we could figure out how to suppress the messages from quad_qag.
Consider
(%i6) f(x) := first(quad_qag(-t^2,t,0,x,6))$
(%i7) plot2d('(f(x)),[x,0,1])$
Compiling gazonk0.lsp.
; (DEFUN COMPILER::CMP-ANON ...) is being compiled.
;; Warning: The variable CONDITIONS::TEMP is not used.
End of Pass 1.
End of Pass 2.
...(yeech! repeated for every computed dot on graph)
Barton