simplify the representation function call in LPCode

CHANGELOG.md

@@ -5,10 +5,11 @@
 
 # News
 
-## v0.9.11-dev
+## v0.9.11
 
 - `hcat` of Tableaux objects
 - `QuantumReedMuller` codes added to the ECC module
+- **(breaking)** change the convention for how to provide a representation function in the constructor of `LPCode` -- strictly speaking a breaking change, but this is not an API that is publicly used in practice
 
 ## v0.9.10 - 2024-09-26
 

Project.toml

@@ -1,7 +1,7 @@
 name = "QuantumClifford"
 uuid = "0525e862-1e90-11e9-3e4d-1b39d7109de1"
 authors = ["Stefan Krastanov <[email protected]> and QuantumSavory community members"]
-version = "0.9.11-dev"
+version = "0.9.11"
 
 [deps]
 Combinatorics = "861a8166-3701-5b0c-9a16-15d98fcdc6aa"

ext/QuantumCliffordHeckeExt/lifted.jl

@@ -22,10 +22,11 @@ The default `GA` is the group algebra of `A[1, 1]`, the default representation `
 
 ## The representation function `repr`
 
-In this struct, we use the default representation function `default_repr` to convert a `GF(2)`-group algebra element to a binary matrix.
+We use the default representation function `Hecke.representation_matrix` to convert a `GF(2)`-group algebra element to a binary matrix.
 The default representation, provided by `Hecke`, is the permutation representation.
 
-We also accept a custom representation function.
+We also accept a custom representation function (the `repr` field of the constructor).
+Whatever the representation, the matrix elements need to be convertible to Integers (e.g. permit `lift(ZZ, ...)`).
 Such a customization would be useful to reduce the number of bits required by the code construction.
 
 For example, if we use a D4 group for lifting, our default representation will be `8×8` permutation matrices,
@@ -54,14 +55,12 @@ struct LiftedCode <: ClassicalCode
     end
 end
 
-default_repr(y::GroupAlgebraElem{FqFieldElem, <: GroupAlgebra}) = Matrix((x -> Bool(Int(lift(ZZ, x)))).(representation_matrix(y)))
-
 """
 `LiftedCode` constructor using the default `GF(2)` representation (coefficients converted to a permutation matrix by `representation_matrix` provided by Hecke).
 """ # TODO doctest example
 function LiftedCode(A::Matrix{GroupAlgebraElem{FqFieldElem, <: GroupAlgebra}}; GA::GroupAlgebra=parent(A[1,1]))
     !(characteristic(base_ring(A[1, 1])) == 2) && error("The default permutation representation applies only to GF(2) group algebra; otherwise, a custom representation function should be provided")
-    LiftedCode(A; GA=GA, repr=default_repr)
+    LiftedCode(A; GA=GA, repr=representation_matrix)
 end
 
 # TODO document and doctest example
@@ -71,7 +70,7 @@ function LiftedCode(group_elem_array::Matrix{<: GroupOrAdditiveGroupElem}; GA::G
         A[i, j] = GA[A[i, j]]
     end
     if repr === nothing
-        return LiftedCode(A; GA=GA, repr=default_repr)
+        return LiftedCode(A; GA=GA, repr=representation_matrix)
     else
         return LiftedCode(A; GA=GA, repr=repr)
     end
@@ -85,12 +84,16 @@ function LiftedCode(shift_array::Matrix{Int}, l::Int; GA::GroupAlgebra=group_alg
             A[i, j] = GA[shift_array[i, j]%l+1]
         end
     end
-    return LiftedCode(A; GA=GA, repr=default_repr)
+    return LiftedCode(A; GA=GA, repr=representation_matrix)
 end
 
-function concat_repr(repr, mat)
-    y = repr.(mat)
-    return hvcat(size(y,1), y...)'
+lift_to_bool(x) = Bool(Int(lift(ZZ,x)))
+
+function concat_lift_repr(repr, mat)
+    x = repr.(mat)
+    y = hvcat(size(x,2), transpose(x)...)
+    z = Matrix(lift_to_bool.(y))
+    return z
 end
 
 function parity_checks(c::LiftedCode)

ext/QuantumCliffordHeckeExt/lifted_product.jl

@@ -72,7 +72,7 @@ julia> code_n(c2), code_k(c2)
 
 ## The representation function
 
-In this struct, we use the default representation function `default_repr` to convert a `GF(2)`-group algebra element to a binary matrix.
+We use the default representation function `Hecke.representation_matrix` to convert a `GF(2)`-group algebra element to a binary matrix.
 The default representation, provided by `Hecke`, is the permutation representation.
 
 We also accept a custom representation function as detailed in [`LiftedCode`](@ref).
@@ -107,24 +107,24 @@ end
 
 # TODO document and doctest example
 function LPCode(A::FqFieldGroupAlgebraElemMatrix, B::FqFieldGroupAlgebraElemMatrix; GA::GroupAlgebra=parent(A[1,1]))
-    LPCode(LiftedCode(A; GA=GA, repr=default_repr), LiftedCode(B; GA=GA, repr=default_repr); GA=GA, repr=default_repr)
+    LPCode(LiftedCode(A; GA=GA, repr=representation_matrix), LiftedCode(B; GA=GA, repr=representation_matrix); GA=GA, repr=representation_matrix)
 end
 
 # TODO document and doctest example
 function LPCode(group_elem_array1::Matrix{<: GroupOrAdditiveGroupElem}, group_elem_array2::Matrix{<: GroupOrAdditiveGroupElem}; GA::GroupAlgebra=group_algebra(GF(2), parent(group_elem_array1[1,1])))
-    LPCode(LiftedCode(group_elem_array1; GA=GA), LiftedCode(group_elem_array2; GA=GA); GA=GA, repr=default_repr)
+    LPCode(LiftedCode(group_elem_array1; GA=GA), LiftedCode(group_elem_array2; GA=GA); GA=GA, repr=representation_matrix)
 end
 
 # TODO document and doctest example
 function LPCode(shift_array1::Matrix{Int}, shift_array2::Matrix{Int}, l::Int; GA::GroupAlgebra=group_algebra(GF(2), abelian_group(l)))
-    LPCode(LiftedCode(shift_array1, l; GA=GA), LiftedCode(shift_array2, l; GA=GA); GA=GA, repr=default_repr)
+    LPCode(LiftedCode(shift_array1, l; GA=GA), LiftedCode(shift_array2, l; GA=GA); GA=GA, repr=representation_matrix)
 end
 
 iscss(::Type{LPCode}) = true
 
 function parity_checks_xz(c::LPCode)
     hx, hz = hgp(c.A, c.B')
-    hx, hz = concat_repr(c.repr,hx), concat_repr(c.repr,hz)
+    hx, hz = concat_lift_repr(c.repr,hx), concat_lift_repr(c.repr,hz)
     return hx, hz
 end