[fnc] improving efficiency for simple natural evaluations #288

Job	Run time
macOS Sonoma Python 3.13 arm64	7m 44s
macOS Sonoma Python 3.12 arm64	9m 18s
macOS Sonoma Python 3.11 arm64	8m 56s
macOS Ventura Python 3.10 arm64 (cross)	12m 3s
macOS Ventura Python 3.9 arm64 (cross)	9m 12s
macOS Ventura Python 3.8 arm64 (cross)	14m 56s
macOS Ventura Python 3.7 arm64 (cross)	13m 59s
macOS Ventura Python 3.6 arm64 (cross)	11m 42s
macOS Ventura Python 3.13 x86_64	14m 9s
macOS Ventura Python 3.12 x86_64	10m 15s
macOS Ventura Python 3.11 x86_64	12m 12s
macOS Ventura Python 3.10 x86_64	12m 30s
macOS Ventura Python 3.9 x86_64	13m 46s
macOS Ventura Python 3.8 x86_64	13m 51s
macOS Ventura Python 3.7 x86_64	19m 19s
macOS Ventura Python 3.6 x86_64	16m 56s
	3h 20m 48s

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