tests and roots for simple reader

swolchok · swolchok · commit b1d354d4072b · 2010-01-05T00:47:04.000-05:00
diff --git a/roots.py b/roots.py
@@ -0,0 +1,54 @@
+'''Roots of Lisp primitives in Python.
+Let's see how far we can get embedding an Arc-like Lisp in Python.
+'''
+
+# We can't use tuples here because we need mutable cons cells.
+# Objects are big and slow.
+cons = lambda x, y: [x,y]
+car = lambda x: x[0]
+cdr = lambda x: x[1]
+
+nil = None
+# Atom is a problem: we're going to expose Python 2-tuples in our Lisp
+# eventually, and those are probably atoms. Let's just get it working
+# and then we'll worry about the distinction; the associated car/cdr
+# implementations are bad too.
+atom = lambda x: not (isinstance(x, tuple) and len(x) == 2)
+
+# Readable types:
+# - lists
+# - strings
+# - numbers as in Python
+# - symbols
+
+def _topylist(L):
+  acc = []
+  while L is not None:
+    acc.append(car(L))
+    L = cdr(L)
+  return acc
+
+def _toarclist(L):
+  res = nil
+  for x in reversed(L):
+    res = cons(x, res)
+  return res
+
+def last(x):
+  while cdr(x) is not nil:
+    x = cdr(x)
+  return x
+
+def nconc(x, y):
+  if x is nil:
+    return y
+  else:
+    # XXX: representation dependent.
+    last(x)[1] = y
+    return x
+
+def nconc1(x, y):
+  return nconc(x, list(y))
+
+def list(*args):
+  return _toarclist(args)
diff --git a/test_sexpr.py b/test_sexpr.py
@@ -0,0 +1,35 @@
+import unittest
+
+from roots import list
+import sexpr
+
+def interned(L):
+  return [intern(x) for x in L]
+
+class TestSexpr(unittest.TestCase):
+  def testsymbol(self):
+    self.assert_(sexpr.str2sexpr('a')[0] is intern('a'))
+
+  def teststring(self):
+    self.assertEqual(sexpr.str2sexpr('"1"')[0], '1')
+
+  def testnum(self):
+    self.assertEqual(sexpr.str2sexpr('1')[0], 1)
+
+  def testfloat(self):
+    self.assertEqual(sexpr.str2sexpr('0.5')[0], 0.5)
+
+  def testescape(self):
+    self.assertEqual(sexpr.str2sexpr('\\"string\\"')[0], '"string"')
+
+  def testemptylist(self):
+    self.assertEqual(sexpr.str2sexpr('()')[0], list())
+
+  def testshortlist(self):
+    self.assertEqual(sexpr.str2sexpr('(1)')[0], list(1))
+
+  def testlist(self):
+    self.assertEqual(sexpr.str2sexpr('(a b c)')[0], list('a', 'b', 'c'))
+
+if __name__ == '__main__':
+  unittest.main()
