From d6bb9bd762d690897702e209fedc777c18419a36 Mon Sep 17 00:00:00 2001
From: Benjamin Ramhorst <bramhorst27@gmail.com>
Date: Wed, 10 Jun 2020 20:10:34 +0100
Subject: [PATCH] Added infrastructure for Fibonacci's number

---
 testing/fibonacci.cpp             | 23 ++++++++++++++
 testing/fibonacci.txt             | 44 ++++++++++++++++++++++++++
 testing/fibonacci_alternative.cpp | 51 +++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+)
 create mode 100644 testing/fibonacci.cpp
 create mode 100644 testing/fibonacci.txt
 create mode 100644 testing/fibonacci_alternative.cpp

diff --git a/testing/fibonacci.cpp b/testing/fibonacci.cpp
new file mode 100644
index 0000000..670cdba
--- /dev/null
+++ b/testing/fibonacci.cpp
@@ -0,0 +1,23 @@
+#include <iostream>
+using namespace std;
+
+/*
+  Takes one input via stdin, the integer n
+*/
+
+int fib(const int n){
+  int y;
+  if (n <= 1) {
+    y = 1;
+  }else {
+    y = fib(n-1);
+    y = y + fib(n-2);
+  }
+  return y;
+}
+
+int main(){
+  int n;
+  cin >> n;
+  cout << fib(n) << endl;
+}
diff --git a/testing/fibonacci.txt b/testing/fibonacci.txt
new file mode 100644
index 0000000..8867dda
--- /dev/null
+++ b/testing/fibonacci.txt
@@ -0,0 +1,44 @@
+Comments:
+  R1 holds y, as described in the source code
+  R2 holds a, as described in the source code
+  R3 holds b, as described in the source code
+  R4 holds n, as described in the source code
+  R5 holds the output (sum), as described in the source code
+  R6 holds the number 0xB (for jumping to the end of the program)
+  R7 holds the number 0x6 (for jumping back)
+
+(0x0) LDA R1 ##MEMORY_LOCATION_OF_s##                  (loads the seed, s, into R1, which then becomes y as in the source code)
+(0x1) LDA R2 ##MEMORY_LOCATION_OF_a##                  (loads a into R2)
+(0x2) LDA R3 ##MEMORY_LOCATION_OF_b##                  (loads b into R3)
+(0x3) LDA R4 ##MEMORY_LOCATION_OF_n##                  (loads n into R4)
+(0x4) LDA R6 ##MEMORY_LOCATION_CONTAINING_0xA##        (loads 0xB, memory location of program end to R6)
+(0x5) LDA R7 ##MEMORY_LOCATION_CONTAINING_0x6##        (loads 0x6, memory location for jumping back)
+(0x6) JC4 R6 R4                                        (if R4, in this case, n, is equal to 0, then jump to end, STP)
+(0x7) MLA R1 R2 R3                                     (multiply and add, same as in the source code y=y*a+b)
+(0x8) ADD R5 R5 R1                                     (adds y to the sum, so that sum+=y, as in the source code)
+(0x9) SBO R4 R4                                        (decrease R4, i.e. n by one, so no infinite loops occur)
+(0xA) JMP R7                                           (jumps back to check whether n>0 and if so, repeats again)
+(0xB) STP
+
+
+Example that can be used with the instruction generator program:
+LDA R1 0
+LDA R2 1
+LDA R3 2
+LDA R4 3
+LDA R6 4
+LDA R7 5
+JC4 R6 R4
+MLA R1 R2 R3
+ADD R5 R5 R1
+SBO R4 R4
+JMP R7 R6
+STP
+
+Requires setting the following data memory location:
+Set location '0' to value of s;
+Set location '1' to value of a;
+Set location '2' to value of b;
+Set location '3' to value of n;
+Set location '4' to value of 0xB;
+Set location '5' to value of 0x6;
diff --git a/testing/fibonacci_alternative.cpp b/testing/fibonacci_alternative.cpp
new file mode 100644
index 0000000..3c26971
--- /dev/null
+++ b/testing/fibonacci_alternative.cpp
@@ -0,0 +1,51 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int fib(int n){
+  int temp = n; //temporary variable, set equal to n
+  stack <int> s;
+  //if n is non-negative, decrease until reaches zero to fill up stack
+  while(temp>1){
+    s.push(0); //n is not 0 or 1, hence push 0 onto stack, come back later
+    temp--; //prevents an infinite loop
+  }
+  s.push(1);
+  s.push(1);
+
+  //go back, increase temp until equal to n
+  while(temp<n){
+    /*
+      Retrieve the top two elements
+    */
+    int smaller = s.top();
+    s.pop();
+    int larger = s.top();
+    s.pop();
+
+    /*
+      this removes the current element, which is 0, but add it back later, once calculated
+    */
+    s.pop();
+    /*
+      Calculate the next element and add it and then to the top of the stack add the larger of thee previous two values
+    */
+    int current = smaller+larger;
+    s.push(current);
+    s.push(larger);
+    temp++; //prevents an infinite loop
+  }
+  /*
+    the top element is 'bigger', which would be used to calculate next Fibonacci number but this is no longer required,
+    so remove and return top element;
+  */
+  s.pop();
+  return s.top();
+}
+
+
+int main(){
+  int n;
+  cin >> n;
+  cout << fib(n) << endl;
+}