start on State class

Rsconscript

@@ -4,6 +4,7 @@ end
 
 build do
   Environment.new do |env|
+    env["D_IMPORT_PATH"] << "src"
     env.Program("peg-puzzle", glob("src/**/*.d"))
   end
 end

src/main.d

@@ -1,7 +1,9 @@
 import std.stdio;
+import state;
 
 int main(string[] args)
 {
+    State s = new State(3);
     writeln("Peg Puzzle");
     return 0;
 }

src/state.d

@@ -0,0 +1,36 @@
+class State
+{
+    private int m_size;
+    private bool[] m_pegs;
+
+    this(int size)
+    {
+        assert(size >= 3);
+        m_size = size;
+        const int n_pegs = (size * (size + 1)) / 2;
+        m_pegs = new bool[n_pegs];
+        m_pegs[] = true;
+        m_pegs[0] = false;
+    }
+
+    this(State s)
+    {
+        m_size = s.m_size;
+        m_pegs = s.m_pegs.dup;
+    }
+
+    private int peg_index(int row, int col)
+    {
+        return (row * (row + 1)) / 2 + col;
+    }
+
+    bool valid_position(int row, int col)
+    {
+        return (row >= 0) && (row < m_size) && (col >= 0) && (col <= row);
+    }
+
+    bool peg_present(int row, int col)
+    {
+        return m_pegs[peg_index(row, col)];
+    }
+}