## x,y,z are variables; a,b,c are constants

## Invariants over numbers

- unary: x = a, a ? x ? b, x ? a(mod b), …
- n-ary: x ? y, x = ay + bz + c,x = max(y, z), …

## Invariants over sequences

- unary: sorted, invariants over all elements
- with sequence: subsequence, ordering
- with scalar: membership

## Why these invariants?

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