Fix find_if and find_if_not to support infinite ranges #715
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- Add compile-time detection for sentinel-based ranges - Fall back to sequential execution for infinite ranges - Maintain parallel execution for finite ranges - Fixes issue taskflow#534: taskflow::find_if doesn't work with infinite ranges The fix uses SFINAE to detect when E_t (end iterator type) differs from B_t (begin iterator type), indicating a sentinel-based range that cannot use std::distance.
doocman
reviewed
Sep 17, 2025
| part([=, &result]() mutable { | ||
| result = std::find_if(beg, end, predicate); | ||
| })(); | ||
| return; |
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The early return here will not help against the compiler trying to instantiate std::distance further down. You must either wrap the remainder of the function in an else {... for the constexpr branch, or figure out a different way to avoid the std::distance-call.. This feature should be relatively simple to add a test for, so my suggestion is to do just that and make sure that it works. Github action should then try to run that test for various other toolchains.
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The fix uses SFINAE to detect when E_t (end iterator type) differs from B_t (begin iterator type), indicating a sentinel-based range that cannot use std::distance.