project08 template files

08/ProgramFlow/FibonacciSeries/FibonacciSeries.vm

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/8/ProgramFlow/FibonacciSeries/FibonacciSeries.vm
+
+// Puts the first n elements of the Fibonacci series in the memory,
+// starting at address addr. n and addr are given in argument[0] and
+// argument[1], which must be initialized by the caller of this code.
+
+	push argument 1         // sets THAT, the base address of the
+	pop pointer 1           // that segment, to argument[1]
+	push constant 0         // sets the series' first and second
+	pop that 0              // elements to 0 and 1, respectively       
+	push constant 1   
+	pop that 1              
+	push argument 0         // sets n, the number of remaining elements
+	push constant 2         // to be computed, to argument[0] minus 2,
+	sub                     // since 2 elements were already computed.
+	pop argument 0          
+
+label LOOP
+	push argument 0
+	if-goto COMPUTE_ELEMENT // if n > 0, goto COMPUTE_ELEMENT
+	goto END                // otherwise, goto END
+
+label COMPUTE_ELEMENT
+    // that[2] = that[0] + that[1]
+	push that 0
+	push that 1
+	add
+	pop that 2
+	// THAT += 1 (updates the base address of that)
+	push pointer 1
+	push constant 1
+	add
+	pop pointer 1 
+	// updates n-- and loops          
+	push argument 0
+	push constant 1
+	sub
+	pop argument 0          
+	goto LOOP
+
+label END