Reorganize code to make it a bit more modular.

sallyforth/sallyforth.py

@@ -1,22 +1,13 @@
 import os
 import sys
+import atexit
 from kernel import Forth
 from lex import tokenize
 import readline
 
 HistoryFile=".sallyforth"
 
-histfile = os.path.join(os.path.expanduser("~"), HistoryFile)
-
-try:
-    readline.read_history_file(histfile)
-except FileNotFoundError:
-    pass
-
-source_dir = os.path.dirname(os.path.abspath(__file__))
-startup_file = f'{source_dir}/startup.sf'
-
-f = Forth()
+hist_file = os.path.join(os.path.expanduser("~"), HistoryFile)
 
 class Completer:
     def __init__(self, f):
@@ -28,16 +19,31 @@ class Completer:
         except IndexError:
             return None
 
+def setup_readline(history_path, f):
     completer = Completer(f)
-
+    try:
+        readline.read_history_file(history_path)
+    except FileNotFoundError:
+        pass
     readline.parse_and_bind("tab: complete")
     readline.set_completer(completer.complete)
+    def save_history():
+        readline.write_history_file(history_path)
+    atexit.register(save_history)
 
+def setup_forth():
+    f = Forth()
     f.defvar("argv", sys.argv[1::])
 
+    source_dir = os.path.dirname(os.path.abspath(__file__))
+    startup_file = f'{source_dir}/startup.sf'
+
     if os.path.exists(startup_file):
         f.execute_file(startup_file)
 
+    return f
+
+def repl(f):
     while True:
         p = f.evaluate_token('*prompt*')
         try:
@@ -57,6 +63,9 @@ while True:
             print("Error:", exc_value)
             print("Error:", exc_traceback)
     
-readline.write_history_file(histfile)
 
+if __name__ == "__main__":
+    f = setup_forth()
+    setup_readline(hist_file, f)
+    repl(f)
     print("Bye!")