[kupfer] calculator: Improve help, include help() itself and _ (last result)

[Ulrik Sverdrup <usverdrup src gnome org>]

commit 9deec6709ac3c3e7618ba2f0445199bb5a584fc6
Author: Ulrik Sverdrup <ulrik sverdrup gmail com>
Date:   Sat Feb 6 00:55:57 2010 +0100

    calculator: Improve help, include help() itself and _ (last result)

 kupfer/plugin/calculator.py |   43 +++++++++++++++++++++++++++++--------------
 1 files changed, 29 insertions(+), 14 deletions(-)
---
diff --git a/kupfer/plugin/calculator.py b/kupfer/plugin/calculator.py
index 5a6e7b4..eac506a 100644
--- a/kupfer/plugin/calculator.py
+++ b/kupfer/plugin/calculator.py
@@ -17,26 +17,37 @@ class IgnoreResultException (Exception):
 	pass
 
 class KupferSurprise (float):
+	"""kupfer
+
+	cleverness to the inf**inf
+	"""
 	def __call__(self, *args):
 		from kupfer import utils, version
 		utils.show_url(version.WEBSITE)
 		raise IgnoreResultException
 
+class DummyResult (object):
+	def __unicode__(self):
+		return u"<Result of last expression>"
+
 class Help (object):
+	"""help()
+
+	Show help about the calculator
+	"""
 	def __call__(self):
 		import textwrap
 
 		from kupfer import uiutils
 
-		environment = dict(math.__dict__)
-		environment.update(cmath.__dict__)
+		environment = make_environment(last_result=DummyResult())
 		docstrings = []
 		for attr in sorted(environment):
-			if attr.startswith("_"):
+			if attr != "_" and attr.startswith("_"):
 				continue
 			val = environment[attr]
 			if not callable(val):
-				docstrings.append("%s = %s" % (attr, val))
+				docstrings.append(u"%s = %s" % (attr, val))
 				continue
 			try:
 				docstrings.append(val.__doc__)
@@ -61,6 +72,19 @@ class Help (object):
 	def __complex__(self):
 		return self()
 
+def make_environment(last_result=None):
+	"Return a namespace for the calculator's expressions to be executed in."
+	environment = dict(vars(math))
+	environment.update(vars(cmath))
+	# define some constants missing
+	if last_result is not None:
+		environment["_"] = last_result
+	environment["help"] = Help()
+	environment["kupfer"] = KupferSurprise("inf")
+	# make the builtins inaccessible
+	environment["__builtins__"] = {}
+	return environment
+
 def format_result(res):
 	cres = complex(res)
 	parts = []
@@ -86,16 +110,7 @@ class Calculate (Action):
 		brackets_missing = expr.count("(") - expr.count(")")
 		if brackets_missing > 0:
 			expr += ")"*brackets_missing
-
-		environment = dict(math.__dict__)
-		environment.update(cmath.__dict__)
-		# define some constants missing
-		if self.last_result is not None:
-			environment["_"] = self.last_result
-		environment["help"] = Help()
-		environment["kupfer"] = KupferSurprise("inf")
-		# make the builtins inaccessible
-		environment["__builtins__"] = {}
+		environment = make_environment(self.last_result)
 
 		pretty.print_debug(__name__, "Evaluating", repr(expr))
 		try: