If primitives fail, they raise a signal. There is also a primitive for unconditionally raising a signal. Most flavors of K have a primitive called "error trap"

If primitives fail, they raise a signal. There is also a primitive for unconditionally raising a signal. Most flavors of K have a primitive called "error trap" which captures signals emitted by a function application, should they occur: f:{11 22 33 x} .[f;,1;:] 0 22 .[f;,4;:] (1;"index") If a signal is not trapped, K pauses execution and opens the debugger, where a user may interactively inspect the environment, evaluate code, and resume: f 4 index error {11 22 33 x} ^ > x 4 > Overall not that different from try...catch in a garden-variety interpreted language with a REPL.