The Little Schemer would be a good resource. Some here may disagree, though. It uses a Socratic dialogue style that rubs some people the wrong way. But here is

The Little Schemer would be a good resource. Some here may disagree, though. It uses a Socratic dialogue style that rubs some people the wrong way. But here is Norvig's Python eval for a Lisp: def eval(x, env=global_env): "Evaluate an expression in an environment." if isinstance(x, Symbol): # variable reference return env.find(x)[x] elif not isinstance(x, List):# constant return x op, *args = x if op == 'quote': # quotation return args[0] elif op == 'if': # conditional (test, conseq, alt) = args exp = (conseq if eval(test, env) else alt) return eval(exp, env) elif op == 'define': # definition (symbol, exp) = args env[symbol] = eval(exp, env) elif op == 'set!': # assignment (symbol, exp) = args env.find(symbol)[symbol] = eval(exp, env) elif op == 'lambda': # procedure (parms, body) = args return Procedure(parms, body, env) else: # procedure call proc = eval(op, env) vals = [eval(arg, env) for arg in args] return proc(*vals) https://norvig.com/lispy.html https://norvig.com/lispy.html (most of the way down that page)