perf: use closures instead of bound functions

[jonahsnider]

No description provided.

[codspeed-hq]

CodSpeed Performance Report

Merging #704 will improve performances by 18.3%

_{Comparing closures (b27aa8d) with main (e2facb1)}

Summary

⚡ 3 improvements
✅ 3 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	convert 8192 bytes to best	61.2 µs	51.7 µs	+18.3%
⚡	convert 2.5 liters to in3	22.5 µs	19.5 µs	+15%
⚡	parse 10h to ms	82.1 µs	70.5 µs	+16.39%