63 lines
1.6 KiB
C++
63 lines
1.6 KiB
C++
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/*
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Copyright (c) 2013 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include <iostream>
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#include <utility>
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#include "util/test.h"
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#include "util/numerics/mpz.h"
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#include "util/pair.h"
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#include "util/lazy_list.h"
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using namespace lean;
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lazy_list<int> seq(int s) {
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return lazy_list<int>(s, [=]() { return seq(s + 1); });
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}
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lazy_list<int> from(int begin, int step, int end) {
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if (begin > end)
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return lazy_list<int>();
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else
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return lazy_list<int>(begin, [=]() { return from(begin + step, step, end); });
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}
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lazy_list<mpz> fact_list_core(mpz i, mpz n) {
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return lazy_list<mpz>(n, [=]() { return fact_list_core(i+1, n*(i+1)); });
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}
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lazy_list<mpz> fact_list() {
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return fact_list_core(mpz(1), mpz(1));
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}
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template<typename T>
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lazy_list<T> first(unsigned sz, lazy_list<T> l) {
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if (sz == 0 || !l) {
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return lazy_list<T>();
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} else {
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return lazy_list<T>(head(l), [=]() { return first(sz - 1, tail(l)); });
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}
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}
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template<typename T1, typename T2>
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lazy_list<std::pair<T1, T2>> zip(lazy_list<T1> const & l1, lazy_list<T2> const & l2) {
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if (l1 && l2) {
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return lazy_list<std::pair<T1, T2>>(mk_pair(head(l1), head(l2)), [=]() { return zip(tail(l1), tail(l2)); });
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} else {
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return lazy_list<std::pair<T1, T2>>();
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}
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}
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int main() {
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lazy_list<int> l(-10, from(10, 20, 100));
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l = cons(-20, l);
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for (auto c : l) {
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std::cout << c << "\n";
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}
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for (auto c : first(30, zip(seq(1), fact_list()))) {
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std::cout << c.first << " " << c.second << "\n";
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}
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return 0;
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}
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