wiki:TypeNats/Interact1

Version 19 (modified by diatchki, 3 years ago) (diff)

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(NOTE: The rule involving constants but no computation could be generalized to work for variables as well, as long as we know that the variables are in the acceptable ranges. Such information could be computed from the <= model, perhaps.)

Top-level interactions for TypeNat:

TypeNat m

Top-level interactions for <=

m <= n   <=> {m <= n}
0 <= a   <=> True
a <= 0   <=> a ~ 0

Top-level interactions for +.

(m + n ~ k) <=> {m + n == k}

(m + a ~ n) <=> a ~ {n - m}    -- n >= m
(0 + a ~ b) <=> a ~ b

(a + b ~ a) <=> (b ~ 0)
(a + b ~ b) <=> (a ~ 0)

(a + a ~ b) <=> (2 * a ~ b)
(a + b ~ 0) <=> (a ~ 0, b ~ 0) -- XXX: Drop this, follows from <= rules?

(a + m ~ b) <=> (m + a ~ b)    -- simple normalization cuts down on some rules

Top-level interactions for *.

(m * n ~ k) <=> {m * n == k}
(m * a ~ n) <=> a ~ { n / m }    -- m `divides` n, False otherwise

(0 * a ~ b) <=> b ~ 0
(1 * a ~ b) <=> a ~ b
(m * a ~ a) <=> a ~ 0            -- 2 <= m

(a * b ~ 1) <=> (a ~ 1, b ~ 1)
(a * a ~ b) <=> a ^ 2 ~ b

(a * m ~ b) <=> (m * a ~ b)      -- simple normalization cuts down on some rules

Top-level interactions for ^

(m ^ n ~ k) <=> {m ^ n == k}

(m ^ a ~ n) <=> a ~ {log m n}   -- log (base m) of n exists, False otherwise
(1 ^ a ~ b) <=> b ~ 1
(m ^ a ~ a) <=> False           -- m /= 1

(a ^ m ~ n) <=> a ~ {root m n}  -- m-th root of n exists, False otherwise
(a ^ 0 ~ b) <=> b ~ 1
(a ^ 1 ~ b) <=> a ~ b
(a ^ m ~ a) <=> (a <= 1)        -- 2 <= m