//one arg: body static cellpoint eval_lambda_body(void) { stack_push(&vars_stack, args_ref(1)); args_push(stack_top(&vars_stack)); reg = last_exp(); while (is_false(reg)){ args_push(stack_top(&vars_stack)); reg = first_exp(); //eval the exp which isn't the last one with tail_context is a_false args_push(a_false); args_push(reg); reg = eval(); //renew the remain exps args_push(stack_pop(&vars_stack)); reg = rest_exps(); stack_push(&vars_stack, reg); args_push(stack_top(&vars_stack)); reg = last_exp(); } //get the last expression args_push(stack_pop(&vars_stack)); reg = first_exp(); //eval the last expression with the tail_context is a_true args_push(a_true); args_push(reg); reg = eval(); args_pop(1); return reg; }
//two args: exps & tail_context static cellpoint eval_sequence(void) { stack_push(&vars_stack, args_ref(1)); args_push(stack_top(&vars_stack)); reg = last_exp(); while (is_false(reg)){ args_push(stack_top(&vars_stack)); reg = first_exp(); //eval the exp which isn't the last one with tail_context is a_false args_push(a_false); args_push(reg); reg = eval(); //renew the remain exps args_push(stack_pop(&vars_stack)); reg = rest_exps(); stack_push(&vars_stack, reg); args_push(stack_top(&vars_stack)); reg = last_exp(); } //get the last expression args_push(stack_pop(&vars_stack)); reg = first_exp(); //eval the last expression with the second argument (tail_context) args_push(args_ref(2)); args_push(reg); reg = eval(); args_pop(2); return reg; }
object *eval(object *exp, object *env) { object *procedure; object *arguments; object *result; bool tailcall = false; do { if (is_self_evaluating(exp)) return exp; if (is_variable(exp)) return lookup_variable_value(exp, env); if (is_quoted(exp)) return text_of_quotation(exp); if (is_assignment(exp)) return eval_assignment(exp, env); if (is_definition(exp)) return eval_definition(exp, env); if (is_if(exp)) { exp = is_true(eval(if_predicate(exp), env)) ? if_consequent(exp) : if_alternative(exp); tailcall = true; continue; } if (is_lambda(exp)) return make_compound_proc(lambda_parameters(exp), lambda_body(exp), env); if (is_begin(exp)) { exp = begin_actions(exp); while (!is_last_exp(exp)) { eval(first_exp(exp), env); exp = rest_exps(exp); } exp = first_exp(exp); tailcall = true; continue; } if (is_cond(exp)) { exp = cond_to_if(exp); tailcall = true; continue; } if (is_let(exp)) { exp = let_to_application(exp); tailcall = true; continue; } if (is_and(exp)) { exp = and_tests(exp); if (is_empty(exp)) return make_boolean(true); while (!is_last_exp(exp)) { result = eval(first_exp(exp), env); if (is_false(result)) return result; exp = rest_exps(exp); } exp = first_exp(exp); tailcall = true; continue; } if (is_or(exp)) { exp = or_tests(exp); if (is_empty(exp)) { return make_boolean(false); } while (!is_last_exp(exp)) { result = eval(first_exp(exp), env); if (is_true(result)) return result; exp = rest_exps(exp); } exp = first_exp(exp); tailcall = true; continue; } if (is_application(exp)) { procedure = eval(operator(exp), env); arguments = list_of_values(operands(exp), env); if (is_primitive_proc(procedure) && procedure->data.primitive_proc.fn == eval_proc) { exp = eval_expression(arguments); env = eval_environment(arguments); tailcall = true; continue; } if (is_primitive_proc(procedure) && procedure->data.primitive_proc.fn == apply_proc) { procedure = apply_operator(arguments); arguments = apply_operands(arguments); } if (is_primitive_proc(procedure)) return (procedure->data.primitive_proc.fn)(arguments); if (is_compound_proc(procedure)) { env = extend_environment(procedure->data.compound_proc.parameters, arguments, procedure->data.compound_proc.env); exp = make_begin(procedure->data.compound_proc.body); tailcall = true; continue; } return make_error(342, "unknown procedure type"); } // is_application() } while (tailcall); fprintf(stderr, "cannot eval unknown expression type\n"); exit(EXIT_FAILURE); }
static pSlipObject slip_eval(pSlip gd, pSlipObject exp, pSlipEnvironment env) { pSlipObject proc; pSlipObject args; tailcall: if (is_self_evaluating(exp) == S_TRUE) { return exp; } else if (is_variable(exp) == S_TRUE) { return lookup_variable_value(gd, exp, env); } else if (is_quoted(gd, exp) == S_TRUE) { return text_of_quotation(exp); } else if (is_assignment(gd, exp) == S_TRUE) { return eval_assignment(gd, exp, env); } else if (is_definition(gd, exp) == S_TRUE) { return eval_definition(gd, exp, env); } else if (is_if(gd, exp) == S_TRUE) { exp = is_true(gd, slip_eval(gd, if_predicate(exp), env)) == S_TRUE ? if_consequent(exp) : if_alternative(gd, exp); goto tailcall; } else if (is_lambda(gd, exp) == S_TRUE) { return s_NewCompoundProc(gd, lambda_parameters(exp), lambda_body(exp), env); } else if (is_begin(gd, exp) == S_TRUE) { exp = begin_actions(exp); while (!is_last_exp(gd, exp)) { slip_eval(gd, first_exp(exp), env); exp = rest_exps(exp); } exp = first_exp(exp); goto tailcall; } else if (is_cond(gd, exp) == S_TRUE) { exp = cond_to_if(gd, exp); goto tailcall; } else if (is_let(gd, exp) == S_TRUE) { exp = let_to_application(gd, exp); goto tailcall; } else if (is_application(exp) == S_TRUE) { proc = slip_eval(gd, slip_operator(exp), env); if (proc == NULL) return gd->singleton_False; if (proc->type == eType_PRIMITIVE_PROC || proc->type == eType_COMPOUND_PROC) { args = list_of_values(gd, operands(exp), env); if (args == NULL) return gd->singleton_False; if (sIsObject_PrimitiveProc(proc) == S_TRUE) { return proc->data.prim_proc.func(gd, args); } else if (sIsObject_CompoundProc(proc) == S_TRUE) { env = setup_environment(gd, proc->data.comp_proc.env, proc->data.comp_proc.params, args); exp = make_begin(gd, proc->data.comp_proc.code); goto tailcall; } else { throw_error(gd, "unknown procedure type\n"); return gd->singleton_False; } } else return proc; } else { throw_error(gd, "cannot eval unknown expression type\n"); return NULL; } throw_error(gd, "what??\n"); return NULL; }