1 files changed, 174 insertions(+), 0 deletions(-)

A prototype.rb

@@ 0,0 1,174 @@
+# prototype implementation of Forth
+
+def is_num?(x)
+    x !~ /\D/
+end
+
+def feval(str)
+    stack = []
+    ops = {
+        'T' => -> {stack.push(true)},
+        'F' => -> {stack.push(false)},
+        'dup' => -> {
+            x = stack.pop
+            stack.push(x)
+            stack.push(x)
+        },
+        'drop' => -> {
+            stack.pop
+        },
+        'over' => -> {
+            n2, n1 = stack.pop, stack.pop
+            stack.push(n1)
+            stack.push(n2)
+            stack.push(n1)
+        },
+        'swap' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(b)
+            stack.push(a)
+        },
+        'rot' => -> {
+            c, b, a = stack.pop, stack.pop, stack.pop
+            stack.push(b)
+            stack.push(c)
+            stack.push(a)
+        },
+        'and' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(b && a)
+        },
+        'or' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(b || a)
+        },
+        'xor' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(b ^ a)
+        },
+        'invert' => -> {
+            stack.push(!stack.pop)
+        },
+        '+' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(a + b)
+        },
+        '*' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(a * b)
+        },
+        '/' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(a / b)
+        },
+        '<' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(a < b)
+        },
+        '>' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(a > b)
+        },
+        '=' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(a == b)
+        },
+        'mod' => -> {
+            b, a = stack.pop, stack.pop
+            stack.push(a % b)
+        },
+        '2*' => -> {stack.push(stack.pop * 2)},
+        '2/' => -> {stack.push(stack.pop / 2)},
+        '0=' => -> {stack.push(stack.pop == 0)},
+        'print' => -> {print stack.pop}
+    }
+    str.split(' ').each do |x|
+        if is_num? x
+            stack.push x.to_i
+        else
+            ops[x].call
+        end
+    end
+    stack
+end
+
+require "test/unit"
+
+class TestEval < Test::Unit::TestCase
+    def test_plus
+        stack = feval('1 5 +')
+        assert_equal(6, stack[0])
+    end
+
+    def test_plus_2
+        stack = feval('3 1 5 + +')
+        assert_equal(9, stack[0])
+    end
+
+    def test_print
+        $stdout = StringIO.new
+        feval('3 1 5 + + print')
+        assert_equal($stdout.string, '9')
+    end
+
+    def test_div
+        stack = feval('6 2 /')
+        assert_equal(3, stack[0])
+    end
+
+    def test_mod
+        stack = feval('6 2 mod')
+        assert_equal(0, stack[0])
+    end
+
+    def test_2times
+        stack = feval('6 2*')
+        assert_equal(12, stack[0])
+    end
+
+    def test_cmp
+        stack = feval('1 0=')
+        assert_equal(false, stack[0])
+        stack = feval('0 0=')
+        assert_equal(true, stack[0])
+        stack = feval('2 1 >')
+        assert_equal(true, stack[0])
+        stack = feval('1 2 <')
+        assert_equal(true, stack[0])
+        stack = feval('1 2 >')
+        assert_equal(false, stack[0])
+        stack = feval('2 1 <')
+        assert_equal(false, stack[0])
+        stack = feval('2 1 =')
+        assert_equal(false, stack[0])
+        stack = feval('1 1 =')
+        assert_equal(true, stack[0])
+        stack = feval('T T and')
+        assert_equal(true, stack[0])
+        stack = feval('T F and')
+        assert_equal(false, stack[0])
+        stack = feval('T F or')
+        assert_equal(true, stack[0])
+        stack = feval('F F or')
+        assert_equal(false, stack[0])
+        stack = feval('T F xor')
+        assert_equal(true, stack[0])
+        stack = feval('T T xor')
+        assert_equal(false, stack[0])
+        stack = feval('T invert T and')
+        assert_equal(false, stack[0])
+    end
+
+    def test_juggling # order is right to left
+        stack = feval('1 2 dup')
+        assert_equal([1, 2, 2], stack)
+        stack = feval('1 2 swap')
+        assert_equal([2, 1], stack)
+        stack = feval('1 2 over')
+        assert_equal([1, 2, 1], stack)
+        stack = feval('1 2 3 rot')
+        assert_equal([2, 3, 1], stack)
+    end
+end
+
+