the.com/invariant
The one thing that stays true while everything around it transforms.
means A property, quantity, or statement that remains unchanged even as the system it belongs to is transformed, shifted, or operated on.
from Built from Latin in- ('not') plus variare ('to vary, change'), the ancestor of 'various' and 'variety.' The word settled into its modern technical sense in 19th-century mathematics, where mathematicians studying transformations — rotating shapes, changing coordinates, substituting variables — needed a name for the quantities that refused to budge no matter what was done to everything else. From there it spread into physics and computer science, always keeping that same job: naming the still point in a turning system.
- loop guardian
- in code, must hold before and after every iteration
- math roots
- Noether linked invariants to conservation laws in 1915
- debug trick
- violated invariants usually mean your bug's root cause
- not constant
- it can vary, just never breaks its defining relationship