add __getitem__ to Register object, update examples

README.md

@@ -23,15 +23,19 @@ We want to reorganize the SDK so that it has a
 comfortable and intuitive interface for developers. I will learn from
 Ismael, Fran, Jorge, and Paco what architecture makes sense and try to
 implement that architecture. This is meant as a place for us to try ideas
-until we settle on something that makes sense for everyone. Right now, users
-can create instances of *QuantumRegister* and *ClassicalRegister*, and bind
+until we settle on something that makes sense for everyone.
+
+Right now, users can create instances of *QuantumRegister* and *ClassicalRegister*, and bind
 these to *QuantumCircuit*. They can then call methods of these objects to
 apply gates within the circuit. The *extensions* directory extends these
-objects as needed to support new gate sets and algorithms.
+objects as needed to support new gate sets and algorithms. The "cswap" gate in
+the standard extension shows how to build gates that are sequences of other
+unitary gates. The Python file "header.py" shows how we append OPENQASM gate
+definitions as we import extensions.
 
-The *qiskit* directory is a Python
+The *qiskit* directory is the main Python
 module. It contains a *qasm* module for parsing OPENQASM circuits,
-an *unroll* module for unrolling QASM to a circuit object, a *circuit* module
+an *unroll* module to flatten QASM for a target gate basis, a *circuit* module
 for representing, transforming, and computing properties of OPENQASM circuits
 as directed acyclic graphs, and a *localize* module for mapping all-to-all
 circuits to run on machines with fixed couplings.

qiskit/_register.py

@@ -36,3 +36,10 @@ class Register(object):
         """Check that j is a valid index into self."""
         if j < 0 or j >= self.sz:
             raise QISKitException("register index out of range")
+
+    def __getitem__(self, key):
+        """Return tuple (self, key) if key is valid."""
+        if not isinstance(key, int):
+            raise QISKitException("expected integer index into register")
+        self.check_range(key)
+        return (self, key)

rippleadd.py

@@ -39,16 +39,16 @@ a.x(0)  # a = 0...0001
 b.x()   # b = 1...1111
 
 # Add a to b, storing result in b
-majority(p, (cin, 0), (b, 0), (a, 0))
+majority(p, cin[0], b[0], a[0])
 for j in range(n-1):
-    majority(p, (a, j), (b, j+1), (a, j+1))
-p.cx((a, n-1), (cout, 0))
+    majority(p, a[j], b[j+1], a[j+1])
+p.cx(a[n-1], cout[0])
 for j in reversed(range(n-1)):
-    unmajority(p, (a, j), (b, j+1), (a, j+1))
-unmajority(p, (cin, 0), (b, 0), (a, 0))
+    unmajority(p, a[j], b[j+1], a[j+1])
+unmajority(p, cin[0], b[0], a[0])
 for j in range(n):
-    p.measure((b, j), (ans, j))
-p.measure((cout, 0), (ans, n))
+    p.measure(b[j], ans[j])
+p.measure(cout[0], ans[n])
 
 print("QuantumCircuit OPENQASM")
 print("-----------------------")

teleport.py

@@ -17,10 +17,10 @@ q.cx(1, 2)
 q.barrier()
 q.cx(0, 1)
 q.h(0)
-p.measure((q, 0), (c0, 0))
-p.measure((q, 1), (c1, 0))
+p.measure(q[0], c0[0])
+p.measure(q[1], c1[0])
 q.z(2).c_if(c0, 1)
 q.x(2).c_if(c1, 1)
-p.measure((q, 2), (c2, 0))
+p.measure(q[2], c2[0])
 
 print(p.qasm())

testsdkskel.py

@@ -40,9 +40,9 @@ r.reset(0)
 for i in range(n-1):
     q.cx(i, i+1)
 for i in range(n):
-    p.u1(math.pi / (i+1), (q, i))
-    p.h((q, i))
-    p.measure((q, i), (c, i))
+    p.u1(math.pi / (i+1), q[i])
+    p.h(q[i])
+    p.measure(q[i], c[i])
 q.ccx(0, 1, 2)
 print(p.qasm())
 print(pp.qasm())