initial commit; we have evaluation!

mem.go

@@ -0,0 +1,42 @@
+package main
+
+import "fmt"
+
+// Memory provides an addressable map of integer cells
+type Memory struct {
+	intern   map[int]int
+	nextFree int
+}
+
+// Read takes a starting address and a count of cells to read after it;
+// (0, 2) reads the first two cells out of memory, for example.
+func (m *Memory) Read(addr int, count int) []int {
+	r := []int{}
+	for i := 0; i < count; i++ {
+		r = append(r, m.intern[addr+i])
+	}
+	return r
+}
+
+// Write inserts the given values into memory, overwriting any existing contents,
+// starting at the provided memory address and incrementing upward.
+func (m *Memory) Write(addr int, values []int) error {
+	if addr < 0 {
+		return fmt.Errorf("addr out of range")
+	}
+	for i := range values {
+		m.intern[addr+i] = values[i]
+	}
+	// we've written past our marker, note that
+	if m.nextFree < addr+len(values) {
+		m.nextFree = addr + len(values)
+	}
+	return nil
+}
+
+// NextFreeAddress provides the furthest "out" address, beyond which is uninitialized memory.
+// Old memory is never "reclaimed", even if the program manually 0s it out.
+// If you want to build your own GC, knock yourself out.
+func (m *Memory) NextFreeAddress() int {
+	return m.nextFree
+}