Merge pull request #20 from wildmaples/fibonacci-element-2

Implement `FibonacciElement` and `StaticsTest`

bin/vm-translator

@@ -2,16 +2,20 @@
 
 require_relative '../lib/vm_translator'
 
+vm_translator = VMTranslator.new(STDOUT)
+
 if File.file?(ARGV[0])
   input_file = File.open(ARGV[0])
-  puts VMTranslator.new.translate(input_file)
+  vm_translator.translate(input_file)
 elsif File.directory?(ARGV[0])
   vm_files = Dir[ARGV[0] + "/*.vm"]
-  vm_translator = VMTranslator.new
+  vm_translator.bootstrap
   vm_files.each do |f|
     input_file = File.open(f)
-    puts vm_translator.translate(input_file)
+    vm_translator.translate(input_file)
   end
 else
   raise ArgumentError.new("Make sure your input is a folder or .vm file")
 end
+
+vm_translator.close

examples/FibonacciElement/Main.vm

@@ -0,0 +1,30 @@
+// 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/08/FunctionCalls/FibonacciElement/Main.vm
+
+// Computes the n'th element of the Fibonacci series, recursively.
+// n is given in argument[0].  Called by the Sys.init function 
+// (part of the Sys.vm file), which also pushes the argument[0] 
+// parameter before this code starts running.
+
+function Main.fibonacci 0
+push argument 0
+push constant 2
+lt                     // checks if n<2
+if-goto IF_TRUE
+goto IF_FALSE
+label IF_TRUE          // if n<2, return n
+push argument 0        
+return
+label IF_FALSE         // if n>=2, returns fib(n-2)+fib(n-1)
+push argument 0
+push constant 2
+sub
+call Main.fibonacci 1  // computes fib(n-2)
+push argument 0
+push constant 1
+sub
+call Main.fibonacci 1  // computes fib(n-1)
+add                    // returns fib(n-1) + fib(n-2)
+return

examples/FibonacciElement/Sys.vm

@@ -0,0 +1,15 @@
+// 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/08/FunctionCalls/FibonacciElement/Sys.vm
+
+// Pushes a constant, say n, onto the stack, and calls the Main.fibonacii
+// function, which computes the n'th element of the Fibonacci series.
+// Note that by convention, the Sys.init function is called "automatically" 
+// by the bootstrap code.
+
+function Sys.init 0
+push constant 4
+call Main.fibonacci 1   // computes the 4'th fibonacci element
+label WHILE
+goto WHILE              // loops infinitely

examples/StaticsTest/Class1.vm

@@ -0,0 +1,20 @@
+// 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/08/FunctionCalls/StaticsTest/Class1.vm
+
+// Stores two supplied arguments in static[0] and static[1].
+function Class1.set 0
+push argument 0
+pop static 0
+push argument 1
+pop static 1
+push constant 0
+return
+
+// Returns static[0] - static[1].
+function Class1.get 0
+push static 0
+push static 1
+sub
+return

examples/StaticsTest/Class2.vm

@@ -0,0 +1,20 @@
+// 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/08/FunctionCalls/StaticsTest/Class2.vm
+
+// Stores two supplied arguments in static[0] and static[1].
+function Class2.set 0
+push argument 0
+pop static 0
+push argument 1
+pop static 1
+push constant 0
+return
+
+// Returns static[0] - static[1].
+function Class2.get 0
+push static 0
+push static 1
+sub
+return

examples/StaticsTest/Sys.vm

@@ -0,0 +1,20 @@
+// 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/08/FunctionCalls/StaticsTest/Sys.vm
+
+// Tests that different functions, stored in two different 
+// class files, manipulate the static segment correctly. 
+function Sys.init 0
+push constant 6
+push constant 8
+call Class1.set 2
+pop temp 0 // Dumps the return value
+push constant 23
+push constant 15
+call Class2.set 2
+pop temp 0 // Dumps the return value
+call Class1.get 0
+call Class2.get 0
+label WHILE
+goto WHILE

lib/code_writer.rb

@@ -146,7 +146,7 @@ def write_call(function_name, num_args)
     EOF
     write_push_D_register
 
-    ["LCL", "ARG", "THIS", "THAT"].each do |label|
+    %w[LCL ARG THIS THAT].each do |label|
       @out.puts <<~EOF
         @#{label}
         D=M
@@ -170,7 +170,11 @@ def write_call(function_name, num_args)
       M=D
     EOF
 
-    write_goto(function_name)
+    @out.puts <<~EOF
+      @#{function_name}
+      0;JMP
+    EOF
+
     write_label("return-address#{@label_counter}")
     @label_counter += 1
   end

lib/vm_translator.rb

@@ -3,13 +3,18 @@
 require 'stringio'
 
 class VMTranslator
-  def initialize
-    # TODO: Add bootstrap code
+  def initialize(out)
+    @out = out
+    @code_writer = CodeWriter.new(out)
   end
 
+  def bootstrap
+    code_writer.write_init
+  end
+
+  attr_reader :out, :code_writer
+
   def translate(input_file)
-    out = StringIO.new
-    code_writer = CodeWriter.new(out)
     parser = Parser.new(input_file)
     file_name = File.basename(input_file.path, ".vm")
 
@@ -37,8 +42,9 @@ def translate(input_file)
         warn("Unknown command type passed into VMTranslator")
       end
     end
+  end
 
+  def close
     code_writer.close
-    out.string
   end
 end