microsoft/Terminal

adjust associative containers to support heterogeneous lookup

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#972 opened on May 24, 2019

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Description

Heterogeneous lookup has been supported since C++14. To quote the linked article,

C++14 allows the lookup to be done via an arbitrary type, so long as the comparison operator can compare that type with the actual key type. This would allow a map from std::string to some value to compare against a const char* or any other type for which an operator< overload is available. It is also useful for indexing composite objects in a std::set by the value of a single member without forcing the user of find to create a dummy object (for example creating an entire struct Person to find a person by name).

Now, it's magic in that you enable it by specifying std::less<> as the third template argument to an associative container; that is:

std::map<std::string, std::string             > map1;
std::map<std::string, std::string, std::less<>> map2;

map2 supports heterogeneous lookup, whereas map1 does not.

Contributor guide

Research direction
Identify all associative container declarations (std::map, std::set, etc.) in the codebase and add std::less<> as the third template parameter. Test for any compilation issues.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75