return nil (empty list) if there's nothing else to return

2 files changed, 20 insertions, 13 deletions

diff --git a/std.py b/std.py
index 7d69345..9496a95 100644
--- a/std.py
+++ b/std.py
@@ -16,12 +16,11 @@ def _get_debug():
 def std_exit(status=None):
     out = 0 if status is None else status.value
     sys.exit(out)
-    return NebBool(True)  # this should never be reached
+    return NebNil()
 
 def std_print(arg):
     print(arg.value)
-    #return []  # TODO this should return empty list
-    return NebBool(True)
+    return NebNil()
 
 def std_print_all(arg):
     for idx, item in enumerate(arg.items):
@@ -31,17 +30,17 @@ def std_print_all(arg):
             raise exception("print-all needs all strings!")
     for x in arg.items:
         std_print(x)
-    return NebBool(True)
+    return NebNil()
     
 def std_debug_on():
     global DEBUG
     DEBUG = True
-    return NebBool(True)
+    return NebNil()
 
 def std_debug_off():
     global DEBUG
     DEBUG = False
-    return NebBool(True)
+    return NebNil()
 
 # math
 def std_add(arg, rest):
@@ -109,7 +108,8 @@ def std_if(cond, t_branch, f_branch=None):
             return evaluate_expression(f_branch)
         else:
             return f_branch
-    return NebBool(True)
+    #return NebBool(True)
+    return NebNil()
 
 # type validation
 def std_is_string(arg):
@@ -242,19 +242,19 @@ def evaluate_expression(expr):
     raise Exception(f"'{expr.symbol.name}' called with unknown signature: '{expr.in_sig()}'")
 
 def build_std():
-    print_string = FuncImpl(NebFunction("print", [NebString], NebString), std_print)
+    print_string = FuncImpl(NebFunction("print", [NebString], NebNil), std_print)
     STD["print"] = [print_string]
 
-    print_all = FuncImpl(NebFunction("print-all", [NebList], NebBool), std_print_all)
+    print_all = FuncImpl(NebFunction("print-all", [NebList], NebNil), std_print_all)
     STD["print-all"] = [print_all]
 
-    exit_ = FuncImpl(NebFunction("exit", [], NebBool), std_exit)
-    exit_int = FuncImpl(NebFunction("exit", [NebInt], NebBool), std_exit)
+    exit_ = FuncImpl(NebFunction("exit", [], NebNil), std_exit)
+    exit_int = FuncImpl(NebFunction("exit", [NebInt], NebNil), std_exit)
     STD["exit"] = [exit_, exit_int]
 
-    debug_on = FuncImpl(NebFunction("debug-on", [], NebBool), std_debug_on)
+    debug_on = FuncImpl(NebFunction("debug-on", [], NebNil), std_debug_on)
     STD["debug-on"] = [debug_on]
-    debug_off = FuncImpl(NebFunction("debug-off", [], NebBool), std_debug_off)
+    debug_off = FuncImpl(NebFunction("debug-off", [], NebNil), std_debug_off)
     STD["debug-off"] = [debug_off]
 
     # arithmetic
diff --git a/tokens.py b/tokens.py
index 1f1fe1b..6e4ba86 100644
--- a/tokens.py
+++ b/tokens.py
@@ -140,3 +140,10 @@ class NebList(NebAny):
             out += f"{item} "
         return f"{out}]"
 
+class NebNil(NebList):
+    def __init__(self):
+        super().__init__([])
+
+    def __str__(self):
+        return "()"
+