halt and quit

halt captures the rest of the pending expression and stops evaluating,
but the interpreter loop keeps running.

quit ends the interpreter session and quits the Thun program.

implementations/Python/simplejoy.py

@@ -499,8 +499,12 @@ def repl(stack=(), dictionary=None):
                 break
             try:
                 stack, _, dictionary = run(text, stack, dictionary)
+            except SystemExit as e:
+                raise SystemExit from e
             except:
                 print_exc()
+    except SystemExit as e:
+        raise SystemExit from e
     except:
         print_exc()
     print()
@@ -543,9 +547,13 @@ def interp(stack=(), dictionary=None):
                 print(e)
             except NotAListError as e:
                 print(e)
+            except SystemExit as e:
+                raise SystemExit from e
             except:
                 print_exc()
             print(stack_to_string(stack))
+    except SystemExit as e:
+        raise SystemExit from e
     except:
         print_exc()
     return stack
@@ -723,6 +731,22 @@ def loop(stack, expr, dictionary):
     return stack, expr, dictionary
 
 
+@inscribe
+def halt(stack, expr, dictionary):
+    '''
+    Put the pending expression onto the stack and halt.
+    '''
+    return (expr, stack), (), dictionary
+
+
+@inscribe
+def quit(stack, expr, dictionary):
+    '''
+    Stop the interpreter.
+    '''
+    raise SystemExit
+
+
 '''
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 ██╔════╝██╔═══██╗██╔══██╗██╔════╝    ██║    ██║██╔═══██╗██╔══██╗██╔══██╗██╔════╝
@@ -1218,4 +1242,7 @@ if __name__ == '__main__':
     J = interp if '-q' in sys.argv else repl
     dictionary = initialize()
     Def.load_definitions(DEFS.splitlines(), dictionary)
-    stack = J(dictionary=dictionary)
+    try:
+        stack = J(dictionary=dictionary)
+    except SystemExit:
+        pass