Address PR review comments

examples/scripts/trace_example.py

@@ -27,13 +27,14 @@
 """
 Initialize tracing. JIT must be disabled for correct tracing.
 
-The call tracing mechanism prints the name, arguments, and return
-values of functions/methods as they are called. Module and class
-names are printed in light red, function and method names in dark
-red, arguments and return values in light blue, and the names of
-registered variables in light yellow. When a method defined in a
-class is called for an object of a derived class type, the class
-of that object is printed in light magenta, in square brackets.
+The call tracing mechanism prints the name, arguments, and return values
+of functions/methods as they are called. Module and class names are
+printed in light red, function and method names in dark red, arguments
+and return values in light blue, and the names of registered variables
+in light yellow. When a method defined in a class is called for an object
+of a derived class type, the class of that object is printed in light
+magenta, in square brackets. Function names and return values are
+distinguished by initial ">>" and "<<" characters respectively.
 """
 jax.config.update("jax_disable_jit", True)
 trace_scico_calls()
@@ -79,7 +80,7 @@ class is called for an object of a derived class type, the class
 g_list = [lmbda * functional.L1Norm(), functional.NonNegativeIndicator()]
 C_list = [linop.Identity((n)), linop.Identity((n))]
 rho_list = [1.0, 1.0]
-maxiter = 10  # number of ADMM iterations
+maxiter = 1  # number of ADMM iterations (set to small value to simplify trace output)
 
 register_variable(f, "f")
 register_variable(g_list[0], "g_list[0]")

scico/trace.py

@@ -24,7 +24,10 @@
 
 When a method defined in a class is called for an object of a derived
 class type, the class of that object is displayed in light magenta, in
-square brackets.
+square brackets. Function names and return values are distinguished by
+initial ``>>`` and ``<<`` characters respectively.
+
+A usage example is provided in the script :code:`trace_example.py`.
 """
 
 
@@ -232,7 +235,7 @@ def wrapper(*args, **kwargs):
         # print representation of return value
         if ret is not None and call_trace.show_return_value:
             print(
-                f"{clr_main}>> {' ' * 2 * call_trace.trace_level}{clr_retv}"
+                f"{clr_main}<< {' ' * 2 * call_trace.trace_level}{clr_retv}"
                 f"{_trace_arg_repr(ret)}{clr_reset}",
                 file=sys.stderr,
             )