starred/terminal
1
0
Fork 0
mirror of https://github.com/microsoft/terminal.git synced 2026-09-23 15:34:31 +00:00
Code Issues 19.0k Packages Projects Releases 20 Wiki Activity

til::coalesce<T> should be able to take a function that returns T #20451

New Issue
Open
opened 2026-01-31 07:14:19 +00:00 by claunia · 1 comment
claunia commented 2026-01-31 07:14:19 +00:00
Owner
Copy Link

Originally created by @zadjii-msft on GitHub (Sep 7, 2023).

From a teams chat

example 1

int Foo() {...}
optional<int> whatever { /*...*/ };
...

int a = til::coalese(whatever, Foo)

Foo only gets called if whatever is empty.

example 2

class Foo{
  optional<int> _cached;
  int GetThing();
  int _generate();
}

int Foo::GetThing()
{
    _cached = coalesce(_cached, [&](){ return _generate(); });
    return _cached;
}
int Foo::_generate() { /*...*/ }

Look ma, now it's easy to implement lazy properties. So easy in fact...

example 3 - til::lazy_property<T>

class Foo {
  til::lazy_property<int> Thing { { this, &Foo::_generate } }; // same syntax as winrt event handlers
  int _generate();
}

// ...

Foo foo{};
int x = foo.Thing(); // Calls _generate
int y = foo.Thing(); // Doesn't
foo.Thing.invalidate(); 
int z = foo.Thing(); // calls generate again

(maybe we don't do this one. Seems like it's potentially footgun-y)

This is a truly one of the ideas I had while working on Profile::EvaluatedIcon in #15843

Originally created by @zadjii-msft on GitHub (Sep 7, 2023). From a teams chat ### example 1 ```c++ int Foo() {...} optional<int> whatever { /*...*/ }; ... int a = til::coalese(whatever, Foo) ``` `Foo` only gets called if `whatever` is empty. ### example 2 ```c++ class Foo{ optional<int> _cached; int GetThing(); int _generate(); } int Foo::GetThing() { _cached = coalesce(_cached, [&](){ return _generate(); }); return _cached; } int Foo::_generate() { /*...*/ } ``` Look ma, now it's easy to implement lazy properties. So easy in fact... ### example 3 - `til::lazy_property<T>` ```c++ class Foo { til::lazy_property<int> Thing { { this, &Foo::_generate } }; // same syntax as winrt event handlers int _generate(); } // ... Foo foo{}; int x = foo.Thing(); // Calls _generate int y = foo.Thing(); // Doesn't foo.Thing.invalidate(); int z = foo.Thing(); // calls generate again ``` (maybe we don't do this one. Seems like it's potentially footgun-y) --- This is a truly one of the ideas I had while working on `Profile::EvaluatedIcon` in #15843
claunia added the Help WantedIssue-TaskProduct-MetaArea-CodeHealth labels 2026-01-31 07:14:20 +00:00
claunia commented 2026-01-31 07:14:20 +00:00
Author
Owner
Copy Link

@lhecker commented on GitHub (Sep 7, 2023):

Parts of the coalesce code will become obsolete with C++23 and the 3 monadic functions listed here: https://en.cppreference.com/w/cpp/utility/optional
If we want to do this, I think we should take inspiration from those for the design.

@lhecker commented on GitHub (Sep 7, 2023): Parts of the coalesce code will become obsolete with C++23 and the 3 monadic functions listed here: https://en.cppreference.com/w/cpp/utility/optional If we want to do this, I think we should take inspiration from those for the design.
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
⛺ Reserved
A11yCO
A11yMAS
A11ySev1
A11ySev2
A11ySev3
A11yTTValidated
A11yUsable
A11yVoiceAccess
A11yWCAG
Area-Accessibility
Area-AtlasEngine
Area-AzureShell
Area-Build
Area-Build
Area-Chat
Area-CmdPal
Area-CodeHealth
Area-Commandline
Area-CookedRead
Area-DefApp
Area-Extensibility
Area-Fonts
Area-GroupPolicy
Area-i18n
Area-Input
Area-Interaction
Area-Interop
Area-Localization
Area-Output
Area-Performance
Area-Portable
Area-Quality
Area-Remoting
Area-Rendering
Area-Schema
Area-Server
Area-Settings
Area-SettingsUI
Area-ShellExtension
Area-ShellExtension
Area-ShellExtension
Area-Suggestions
Area-Suggestions
Area-TerminalConnection
Area-TerminalControl
Area-Theming
Area-UserInterface
Area-VT
Area-Windowing
Area-WPFControl
AutoMerge
Blocking-Ingestion
Culprit-Centennial
Culprit-WinUI
Disability-All
Disability-Blind
Disability-LowVision
Disability-Mobility
External-Blocked-WinUI3
Fixed
Gathering-Data
good first issue
HCL-E+D
HCL-WindowsTerminal
Help Wanted
Impact-Compatibility
Impact-Compliance
Impact-Correctness
Impact-Visual
In-PR
InclusionBacklog
InclusionBacklog-Windows TerminalWin32
InclusionCommitted-202206
Issue-Bug
Issue-Docs
Issue-Feature
Issue-Feature
Issue-Question
Issue-Samples
Issue-Scenario
Issue-Task
Needs-Attention
Needs-Author-Feedback
Needs-Bisect
Needs-Discussion
Needs-Repro
Needs-Tag-Fix
Needs-Tag-Fix
Needs-Triage
No-Recent-Activity
Priority-0
Priority-1
Priority-2
Priority-3
Product-Cmd.exe
Product-Colortool
Product-Colortool
Product-Colortool
Product-Conhost
Product-Conpty
Product-Meta
Product-Powershell
Product-Terminal
Product-WSL
pull-request
Mirrored from GitHub Pull Request
 Resolution-Answered
Resolution-By-Design
Resolution-Duplicate
Resolution-External
Resolution-Fix-Available
Resolution-Fix-Committed
Resolution-No-Repro
Resolution-Won't-Fix
Severity-Blocking
Severity-Crash
Severity-DataLoss
spam
this-will-be-a-breaking-change
Tracking-External
WindowsTerminal_Win32
Work-Item
zAskModeBug
zInbox-Bug
No Label Area-CodeHealth Help Wanted Issue-Task Product-Meta
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
claunia
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: starred/terminal#20451
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?