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feat(util/lazy_list_fn): handle the 'is_nil' case more efficiently

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Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commit is contained in:
Leonardo de Moura 2014-07-03 11:29:04 -07:00
parent c9cfb844f1
commit db0ef64c04
1 changed files with 79 additions and 57 deletions
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24
src/util/lazy_list_fn.h
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@ -30,7 +30,7 @@ void for_each(lazy_list<T> l, F && f) {
*/
template<typename T>
lazy_list<T> take(unsigned sz, lazy_list<T> const & l) {
if (sz == 0) {
if (sz == 0 || l.is_nil()) {
return lazy_list<T>();
} else {
return mk_lazy_list<T>([=]() {
@ -62,6 +62,11 @@ lazy_list<T> to_lazy(list<T> l) {
*/
template<typename T>
lazy_list<T> append(lazy_list<T> const & l1, lazy_list<T> const & l2, char const * cname = "lazy list") {
if (l1.is_nil())
return l2;
else if (l2.is_nil())
return l1;
else
return mk_lazy_list<T>([=]() {
auto p = l1.pull();
if (!p) {
@ -78,6 +83,9 @@ lazy_list<T> append(lazy_list<T> const & l1, lazy_list<T> const & l2, char const
*/
template<typename T>
lazy_list<T> orelse(lazy_list<T> const & l1, lazy_list<T> const & l2, char const * cname = "lazy list") {
if (l1.is_nil())
return l2;
else
return mk_lazy_list<T>([=]() {
auto p = l1.pull();
if (!p) {
@ -95,6 +103,11 @@ lazy_list<T> orelse(lazy_list<T> const & l1, lazy_list<T> const & l2, char const
*/
template<typename T>
lazy_list<T> interleave(lazy_list<T> const & l1, lazy_list<T> const & l2, char const * cname = "lazy list") {
if (l1.is_nil())
return l2;
else if (l2.is_nil())
return l1;
else
return mk_lazy_list<T>([=]() {
auto p = l1.pull();
if (!p) {
@ -111,6 +124,9 @@ lazy_list<T> interleave(lazy_list<T> const & l1, lazy_list<T> const & l2, char c
*/
template<typename T, typename F>
lazy_list<T> map(lazy_list<T> const & l, F && f, char const * cname = "lazy list") {
if (l.is_nil())
return l;
else
return mk_lazy_list<T>([=]() {
auto p = l.pull();
if (!p) {
@ -127,6 +143,9 @@ lazy_list<T> map(lazy_list<T> const & l, F && f, char const * cname = "lazy list
*/
template<typename To, typename From, typename F>
lazy_list<To> map2(lazy_list<From> const & l, F && f, char const * cname = "lazy list") {
if (l.is_nil())
return lazy_list<To>();
else
return mk_lazy_list<To>([=]() {
typename lazy_list<From>::maybe_pair p = l.pull();
if (!p) {
@ -147,6 +166,9 @@ lazy_list<To> map2(lazy_list<From> const & l, F && f, char const * cname = "lazy
*/
template<typename T, typename P>
lazy_list<T> filter(lazy_list<T> const & l, P && pred, char const * cname = "lazy list") {
if (l.is_nil())
return l;
else
return mk_lazy_list<T>([=]() {
auto p = l.pull();
if (!p) {