fixes for term heads

Author: shashi

src/types.jl

@@ -441,7 +441,7 @@ setargs(t, args) = Term{symtype(t)}(operation(t), args)
 cdrargs(args) = setargs(t, cdr(args))
 
 print_arg(io, x::Union{Complex, Rational}; paren=true) = print(io, "(", x, ")")
-isbinop(f) = istree(f) && Base.isbinaryoperator(nameof(operation(f)))
+isbinop(f) = istree(f) && !istree(operation(f)) && Base.isbinaryoperator(nameof(operation(f)))
 function print_arg(io, x; paren=false)
     if paren && isbinop(x)
         print(io, "(", x, ")")