if you use true? as checking function for list, be attention to: blank list -> '(), would not match it.
> (true? '())
nil
If you often use it, advise you use :
> (define (bool x) (if (nil? x) nil true))
> (for-all bool '(1 2 3 4 () 6))
Quote from: "ssqq"
> (true? '())
nil
`true?` works as advertised.
http://www.newlisp.org/downloads/newlisp_manual.html#truep
I don't see any problem with it, and so I don't consider it "dangerous".