Add a "quiet" mode.

This brings the Python Joy interpreter into better congruence with the
Nim interpreter for ease of automated testing.

README

@@ -64,6 +64,12 @@ To start a crude REPL:
 
     python -m joy
 
+There is a "quiet" mode for e.g. using joy from a shell script:
+
+    python -m joy -q
+
+This supresses the initial banner output and the prompt text.
+
 
 §.3 Documentation
 

joy/__main__.py

@@ -17,13 +17,19 @@
 #    You should have received a copy of the GNU General Public License
 #    along with Thun.  If not see <http://www.gnu.org/licenses/>.
 #
+import sys
 from .library import initialize, inscribe
-from .joy import repl
+from .joy import repl, interp
 from .utils.pretty_print import trace
 
 
 inscribe(trace)
-print('''\
+
+if '-q' in sys.argv:
+	j = interp
+else:
+	j = repl
+	print('''\
 Thun - Copyright © 2017 Simon Forman
 This program comes with ABSOLUTELY NO WARRANTY; for details type "warranty".
 This is free software, and you are welcome to redistribute it
@@ -31,4 +37,4 @@ under certain conditions; type "sharing" for details.
 Type "words" to see a list of all words, and "[<name>] help" to print the
 docs for a word.
 ''')
-stack = repl(dictionary=initialize())
+stack = j(dictionary=initialize())

joy/joy.py

@@ -107,3 +107,25 @@ def repl(stack=(), dictionary=None):
 		print_exc()
 	print()
 	return stack
+
+
+def interp(stack=(), dictionary=None):
+	'''
+	Simple REPL with no extra output, suitable for use in scripts.
+	'''
+	if dictionary is None:
+		dictionary = {}
+	try:
+		while True:
+			try:
+				text = input()
+			except (EOFError, KeyboardInterrupt):
+				break
+			try:
+				stack, _, dictionary = run(text, stack, dictionary)
+			except:
+				print_exc()
+			print(stack_to_string(stack))
+	except:
+		print_exc()
+	return stack