[lispm]

Error messages and stack traces look pretty ugly.

In Common Lisp:

    CL-USER 51 > (bake (make-instance 'pie :flavor :blackberry) 375 10.25)

    Error: The value 3843.75 of #:|predicate1555| is not a predicate in CONDP.
      1 (continue) Supply a new value of #:|predicate1555|.
      2 (abort) Return to level 0.
      3 Return to top loop level 0.

A clear error message and a way to repair it.

A stack frame:

    Call to BAKE {offset 394}
      PIE               : #<PIE 402000993B>
      TEMP              : 375
      TIME              : 10.25
      DBG::|predicate|  : 3843.75
      DBG::|expression| : #<Function < 411007995C>
      DBG::G            : 3843.75

[coldtea]

Which CL is that?

[lispm]

LispWorks, the one Rich Hickey used for quite some time... ;-)

[coldtea]

Yeah, I feared that. That's the paid-for one, isn't it?