From eb27595cd5dae3b7eb61247c3e2569f226d55cc2 Mon Sep 17 00:00:00 2001
From: Andrew Keeton <andrewrkeeton@gmail.com>
Date: Thu, 6 Nov 2014 20:00:09 -0500
Subject: [PATCH 1/3] Add branch_if_positive_test().

---
 src/machine.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/machine.rs b/src/machine.rs
index 5372e3d..54df5a4 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -956,3 +956,16 @@ fn branch_if_minus_test() {
         assert_eq!(machine.registers.program_counter, Address(0xABCD));
     }
 }
+
+#[test]
+fn branch_if_positive_test() {
+    let mut machine = Machine::new();
+
+    machine.registers.status.insert(PS_NEGATIVE);
+    machine.branch_if_positive(Address(0xABCD));
+    assert_eq!(machine.registers.program_counter, Address(0));
+
+    machine.registers.status.remove(PS_NEGATIVE);
+    machine.branch_if_positive(Address(0xABCD));
+    assert_eq!(machine.registers.program_counter, Address(0xABCD));
+}

From f3160e1bcc7fd8a431c01e7de367b359077c6a67 Mon Sep 17 00:00:00 2001
From: Andrew Keeton <andrewrkeeton@gmail.com>
Date: Thu, 6 Nov 2014 20:02:40 -0500
Subject: [PATCH 2/3] Add branch_if_positive().

---
 src/machine.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/machine.rs b/src/machine.rs
index 54df5a4..210c46c 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -583,6 +583,12 @@ impl Machine {
         }
     }
 
+    fn branch_if_positive(&mut self, addr: Address) {
+        if !self.registers.status.contains(PS_NEGATIVE) {
+            self.registers.program_counter = addr;
+        }
+    }
+
     fn push_on_stack(&mut self, val: u8) {
         let addr = self.registers.stack_pointer.to_address();
         self.memory.set_byte(addr, val);

From 83d303f878c6701bea7ccd29a24701607d767a2c Mon Sep 17 00:00:00 2001
From: Andrew Keeton <andrewrkeeton@gmail.com>
Date: Thu, 6 Nov 2014 20:04:03 -0500
Subject: [PATCH 3/3] Add BPL to execute_instruction().

---
 src/machine.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/machine.rs b/src/machine.rs
index 210c46c..1980cf0 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -157,6 +157,12 @@ impl Machine {
                 self.branch_if_minus(addr);
             }
 
+            (instruction::BPL, instruction::UseRelative(rel)) => {
+                let addr = self.registers.program_counter
+                         + AddressDiff(rel as i32);
+                self.branch_if_positive(addr);
+            }
+
             (instruction::CLC, instruction::UseImplied) => {
                 self.registers.status.and(!PS_CARRY);
             }