Here, the usage of the Debugger is explained by showing an example for debugging a program which computes the integer factorial by a recursive definition.
% asir
[0] load("fac")$
[3] debug$
(debug) list factorial
1 def factorial(X) {
2 if ( !X )
3 return 1;
4 else
5 return X * factorial(X - 1);
6 }
7 end$
(debug) stop at 5 <-- setting a break point
(0) stop at "./fac":5
(debug) quit <-- leaving the debug-mode
[4] factorial(6); <-- call for factorial(6)
stopped in factorial at line 5 in file "./fac"
5 return X * factorial(X - 1);
(debug) where <-- display the calling sequence up to
factorial(), line 5 in "./fac" this break point
(debug) print X <-- Display the value of X
X = 6
(debug) step <-- step execution (enters function)
stopped in factorial at line 2 in file "./fac"
2 if ( !X )
(debug) where
factorial(), line 2 in "./fac"
factorial(), line 5 in "./fac"
(debug) print X
X = 5
(debug) delete 0 <-- delete the break point 0
(debug) cont <-- continue execution
720 <-- result = 6!
[5] quit;
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