[clisp-list] debugging help

[David M. <sv...@ya...>]

Sorry for the newbie question, but how would you use the debugger to 
figure out what line of code is calling a structure slot reader with nil?



[39]> (find-best-outcome (fen-pos "r7/8/8/8/8/8/8/R6b w - - 0 1") 3)

*** - SYSTEM::%STRUCTURE-REF: NIL is not a structure of type POS
1. Break [40]> :bt

EVAL frame for form (FIND-BEST-OUTCOME (FEN-POS "r7/8/8/8/8/8/8/R6b w - 
- 0 1") 3)
1. Break [40]>