BSD-2-Clause licensed by Christiaan Baaij
This version can be pinned in stack with:ghc-typelits-natnormalise-0.5.9@sha256:06ff00694337cb5445f7e2e30a937332634a6d6de2fd6cd9da047f7ec6385a9c,3226
Module documentation for 0.5.9
ghc-typelits-natnormalise
A type checker plugin for GHC that can solve equalities
of types of kind Nat, where these types are either:
- Type-level naturals
- Type variables
- Applications of the arithmetic expressions
(+,-,*,^).
It solves these equalities by normalising them to sort-of
SOP (Sum-of-Products) form, and then perform a
simple syntactic equality.
For example, this solver can prove the equality between:
(x + 2)^(y + 2)
and
4*x*(2 + x)^y + 4*(2 + x)^y + (2 + x)^y*x^2
Because the latter is actually the SOP normal form
of the former.
To use the plugin, add
{-# OPTIONS_GHC -fplugin GHC.TypeLits.Normalise #-}
To the header of your file.
0.5.9 March 17th 2018
- Add support for GHC 8.4.1
0.5.8 January 4th 2018
- Add support for GHC 8.4.1-alpha1
0.5.7 November 7th 2017
- Solve inequalities such as:
1 <= a + 3
0.5.6 October 31st 2017
- Fixes bugs:
(x + 1) ~ (2 * y) no longer implies ((2 * (y - 1)) + 1) ~ x
0.5.5 October 22nd 2017
- Solve inequalities when their normal forms are the same, i.e.
(2 <= (2 ^ (n + d))) implies (2 <= (2 ^ (d + n)))
- Find more unifications:
8^x - 2*4^x ~ 8^y - 2*4^y ==> [x := y]
0.5.4 October 14th 2017
- Perform normalisations such as:
2^x * 4^x ==> 8^x
0.5.3 May 15th 2017
0.5.2 January 15th 2017
- Fixes bugs:
- Reification from SOP to Type sometimes loses product terms
0.5.1 September 29th 2016
- Fixes bugs:
- Cannot solve an equality for the second time in a definition group
0.5 August 17th 2016
- Solve simple inequalities, i.e.:
a <= a + 12a <= 3a1 <= a^b
0.4.6 July 21th 2016
- Reduce “x^(-y) * x^y” to 1
- Fixes bugs:
- Subtraction in exponent induces infinite loop
0.4.5 July 20th 2016
- Fixes bugs:
- Reifying negative exponent causes GHC panic
0.4.4 July 19th 2016
- Fixes bugs:
- Rounding error in
logBase calculation
0.4.3 July 18th 2016
- Fixes bugs:
- False positive: “f :: (CLog 2 (2 ^ n) ~ n, (1 <=? n) ~ True) => Proxy n -> Proxy (n+d)”
0.4.2 July 8th 2016
- Find more unifications:
(2*e ^ d) ~ (2*e*a*c) ==> [a*c := 2*e ^ (d-1)]a^d * a^e ~ a^c ==> [c := d + e]x+5 ~ y ==> [x := y - 5], but only when x+5 ~ y is a given constraint
0.4.1 February 4th 2016
- Find more unifications:
F x y k z ~ F x y (k-1+1) z ==> [k := k], where F can be any type function
0.4 January 19th 2016
- Stop using ‘provenance’ hack to create conditional evidence (GHC 8.0+ only)
- Find more unifications:
F x + 2 - 1 - 1 ~ F x ==> [F x := F x], where F can be any type function with result Nat.
0.3.2
- Find more unifications:
(z ^ a) ~ (z ^ b) ==> [a := b](i ^ a) ~ j ==> [a := round (logBase i j)], when i and j are integers, and ceiling (logBase i j) == floor (logBase i j).
0.3.1 October 19th 2015
- Find more unifications:
(i * a) ~ j ==> [a := div j i], when i and j are integers, and mod j i == 0.(i * a) + j ~ k ==> [a := div (k-j) i], when i, j, and k are integers, and k-j >= 0 and mod (k-j) i == 0.
0.3 June 3rd 2015
- Find more unifications:
<TyApp xs> + x ~ 2 + x ==> [<TyApp xs> ~ 2]
- Fixes bugs:
- Unifying
a*b ~ b now returns [a ~ 1]; before it erroneously returned [a ~ ], which is interpred as [a ~ 0]…
- Unifying
a+b ~ b now returns [a ~ 0]; before it returned the undesirable, though equal, [a ~ ]
0.2.1 May 6th 2015
- Update
Eq instance of SOP: Empty SOP is equal to 0
0.2 April 22nd 2015
- Finds more unifications:
(2 + a) ~ 5 ==> [a := 3](3 * a) ~ 0 ==> [a := 0]
0.1.2 April 21st 2015
- Don’t simplify expressions with negative exponents
0.1.1 April 17th 2015
0.1 March 30th 2015
