public Procedure(Cell parms, Cell body, Env env)
{
this.parms = parms.list.Select(x => x.symbol).ToList();
this.body = body;
this.env = env;
}
//
// Eval
//
static public Cell Eval(Cell x)
{
return(Eval(x, GlobalEnv));
}
static public Cell Eval(Cell x, Env env)
{
if (x.Type == Cell.CellType.Undefined)
{
throw new Exception("Undefined cell type");
}
// Symbol
if (x.Type == Cell.CellType.Symbol)
{
return(env[x.symbol]);
}
// Number
else if (x.Type != Cell.CellType.List)
{
return(x);
}
// List
if (x.list[0].symbol == "begin")
{
Cell res = null;
foreach (var exp in x.list.Skip(1))
{
res = Eval(exp, env);
}
return(res);
}
else if (x.list[0].symbol == "quote")
{
return(x.list[1]);
}
else if (x.list[0].symbol == "if")
{
var test = x.list[1];
var conseq = x.list[2];
var alt = x.list[3];
var exp = (Eval(test, env).boolval) == true ? conseq : alt;
return(Eval(exp, env));
}
else if (x.list[0].symbol == "define")
{
var variable = x.list[1];
var exp = x.list[2];
env[variable.symbol] = Eval(exp, env);
return(null);
}
else if (x.list[0].symbol == "set!")
{
env[x.list[1].symbol] = Eval(x.list[2], env);
return(null);
}
else if (x.list[0].symbol == "lambda")
{
return(new Cell()
{
proc = new Procedure(x.list[1], x.list[2], env), Type = Cell.CellType.Procedure
});
}
else
{
var proc = Eval(x.list[0], env);
var args = x.list.Skip(1).Select(n => Eval(n, env)).ToList();
if (proc.Type == Cell.CellType.Procedure)
{
// Lambda call
return(proc.proc.Call(args));
}
else
{
// Function call
return((Cell)proc.func.DynamicInvoke(args));
}
}
}
//
// Initialize an environment with some standard functions
//
static Program()
{
GlobalEnv["+"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
number = x[0].number + x[1].number,
Type = Cell.CellType.Number
}),
Type = Cell.CellType.Function
};
GlobalEnv["-"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
number = x[0].number - x[1].number,
Type = Cell.CellType.Number
}),
Type = Cell.CellType.Function
};
GlobalEnv["*"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
number = x[0].number * x[1].number,
Type = Cell.CellType.Number
}),
Type = Cell.CellType.Function
};
GlobalEnv["/"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
number = x[0].number / x[1].number,
Type = Cell.CellType.Number
}),
Type = Cell.CellType.Function
};
GlobalEnv["="] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
boolval = x[0].number == x[1].number,
Type = Cell.CellType.Bool
}),
Type = Cell.CellType.Function
};
GlobalEnv["<"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
boolval = x[0].number < x[1].number,
Type = Cell.CellType.Bool
}),
Type = Cell.CellType.Function
};
GlobalEnv[">"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
boolval = x[0].number > x[1].number,
Type = Cell.CellType.Bool
}),
Type = Cell.CellType.Function
};
GlobalEnv["<="] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
boolval = x[0].number <= x[1].number,
Type = Cell.CellType.Bool
}),
Type = Cell.CellType.Function
};
GlobalEnv[">="] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
boolval = x[0].number >= x[1].number,
Type = Cell.CellType.Bool
}),
Type = Cell.CellType.Function
};
GlobalEnv["car"] = new Cell()
{
func = new Func <List <Cell>, Cell>(x => x[0].list.First()),
Type = Cell.CellType.Function
};
GlobalEnv["cdr"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
list = x[0].list.Skip(1).ToList(),
Type = Cell.CellType.List
}),
Type = Cell.CellType.Function
};
GlobalEnv["cons"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x =>
{
Cell res = new Cell()
{
Type = Cell.CellType.List
};
res.list.Add(x[0]);
res.list.AddRange(x[1].list);
return(res);
}),
Type = Cell.CellType.Function
};
GlobalEnv["append"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x =>
{
Cell res = new Cell()
{
Type = Cell.CellType.List
};
res.list.AddRange(x[0].list);
res.list.AddRange(x[1].list);
return(res);
}),
Type = Cell.CellType.Function
};
GlobalEnv["length"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
number = x[0].list.Count,
Type = Cell.CellType.Number
}),
Type = Cell.CellType.Function
};
GlobalEnv["null?"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
boolval = x[0].list.Count == 0,
Type = Cell.CellType.Bool
}),
Type = Cell.CellType.Function
};
GlobalEnv["list"] = new Cell()
{
func = new Func <List <Cell>, Cell>(
x => new Cell()
{
list = x,
Type = Cell.CellType.List
}),
Type = Cell.CellType.Function
};
}
