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Add a lazyt class for delaying computations #5090

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Merged
merged 2 commits into from
Sep 9, 2019
Merged

Add a lazyt class for delaying computations #5090

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cd07c79
Introduce lazy class
romainbrenguier Sep 5, 2019
8dbbca1
Add unit test for the lazyt class
romainbrenguier Sep 5, 2019
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1 change: 1 addition & 0 deletions unit/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,7 @@ SRC += analyses/ai/ai.cpp \
util/irep_sharing.cpp \
util/json_array.cpp \
util/json_object.cpp \
util/lazy.cpp \
util/memory_info.cpp \
util/message.cpp \
util/optional.cpp \
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29 changes: 29 additions & 0 deletions unit/util/lazy.cpp
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@@ -0,0 +1,29 @@
/*******************************************************************\

Module: Unit tests for lazy

Author: Romain Brenguier, [email protected]

\*******************************************************************/

#include <testing-utils/use_catch.h>
#include <util/lazy.h>

SCENARIO("lazy test", "[core][util][lazy]")
{
std::size_t call_counter = 0;
auto length_with_counter = [&call_counter](const std::string &s) {
++call_counter;
return s.length();
};
auto lazy_length =
lazyt<int>::from_fun([&]() { return length_with_counter("foo"); });
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@LAJW LAJW Sep 6, 2019 •
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😊 https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/lazy-expressions
And now you could even infer return type by doing:

template<T> auto lazy(T func) -> lazyt<decltype(func())> { ... }

Also, () in zero-argument lambdas is optional.

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I'm adding it in a follow-up PR: #5101


REQUIRE(call_counter == 0);
auto result = lazy_length.force();
REQUIRE(call_counter == 1);
REQUIRE(result == 3);
result = lazy_length.force();
REQUIRE(call_counter == 1);
REQUIRE(result == 3);
}