From e16ff766ffe73b4d8507b8b904fdfb4908142c42 Mon Sep 17 00:00:00 2001
From: Tommy Hofmann <thofma@gmail.com>
Date: Thu, 9 Jan 2025 20:46:52 +0100
Subject: [PATCH] fix: add missing hash methods (#1719)
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Co-authored-by: Lars Göttgens <lars.goettgens@rwth-aachen.de>
---
 src/GenOrd/FractionalIdeal.jl |  4 ++++
 src/GrpAb/Map.jl              |  2 ++
 src/Misc/OrdLocalization.jl   |  7 +++++++
 src/RCF/class_fields.jl       |  3 +++
 test/GenOrd/Ideal.jl          | 11 +++++++++++
 test/GrpAb/Map.jl             |  8 ++++++++
 test/Misc/OrdLocalization.jl  | 12 +++++++++++-
 test/RCF/rcf.jl               | 13 +++++++++++++
 8 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/src/GenOrd/FractionalIdeal.jl b/src/GenOrd/FractionalIdeal.jl
index 8cfeb29515..f74b87f38f 100644
--- a/src/GenOrd/FractionalIdeal.jl
+++ b/src/GenOrd/FractionalIdeal.jl
@@ -276,6 +276,10 @@ function ==(A::GenOrdFracIdl, B::GenOrdFracIdl)
   return isone(denominator(C, copy = false)) && isone(norm(C))
 end
 
+function Base.hash(A::GenOrdFracIdl, h::UInt)
+  return hash(order(A), hash(basis_matrix(A), h))
+end
+
 ################################################################################
 #
 #  Colon
diff --git a/src/GrpAb/Map.jl b/src/GrpAb/Map.jl
index 0aa78dde3b..c5d9368411 100644
--- a/src/GrpAb/Map.jl
+++ b/src/GrpAb/Map.jl
@@ -216,6 +216,8 @@ end
 
 ==(f::FinGenAbGroupHom, g::FinGenAbGroupHom) = domain(f) === domain(g) && codomain(f) === codomain(g) && all(x -> f(x) == g(x), gens(domain(f)))
 
+Base.hash(f::FinGenAbGroupHom, h::UInt) = h
+
 ################################################################################
 #
 #  Inverse of a map
diff --git a/src/Misc/OrdLocalization.jl b/src/Misc/OrdLocalization.jl
index 70b693317c..cce4832eb8 100644
--- a/src/Misc/OrdLocalization.jl
+++ b/src/Misc/OrdLocalization.jl
@@ -208,6 +208,13 @@ function ==(a::OrdLocElem{T}, b::OrdLocElem{T}) where {T <: AbsSimpleNumFieldEle
    return data(a) == data(b)
 end
 
+function Base.hash(a::OrdLocElem, h::UInt)
+  b = 0x33dd41cd510034d2%UInt
+  b = xor(hash(parent(a), h), b)
+  b = xor(hash(data(a), h), b)
+  return b
+end
+
 ##############################################################################
 #
 #  Inversion
diff --git a/src/RCF/class_fields.jl b/src/RCF/class_fields.jl
index 9852b165ff..23a4c1763d 100644
--- a/src/RCF/class_fields.jl
+++ b/src/RCF/class_fields.jl
@@ -254,6 +254,9 @@ function ==(a::ClassField, b::ClassField)
   return is_eq(kernel(h[2])[1], kernel(h[1])[1])
 end
 
+function Base.hash(a::ClassField, h::UInt)
+  return hash(base_ring(a), h)
+end
 
 ###############################################################################
 #
diff --git a/test/GenOrd/Ideal.jl b/test/GenOrd/Ideal.jl
index 37dded3327..441f0c1bdc 100644
--- a/test/GenOrd/Ideal.jl
+++ b/test/GenOrd/Ideal.jl
@@ -77,3 +77,14 @@
     end
   end
 end
+
+let
+  # hashing of fractional ideals
+  k = GF(7)
+  kx, x = rational_function_field(k, "x")
+  kt = parent(numerator(x))
+  ky, y = polynomial_ring(kx, "y")
+  F, a = function_field(y^2+x)
+  O = integral_closure(kt, F)
+  @test hash(fractional_ideal(a*O)) == hash(fractional_ideal(a*O))
+end
diff --git a/test/GrpAb/Map.jl b/test/GrpAb/Map.jl
index 9149fd4d52..55a993ca04 100644
--- a/test/GrpAb/Map.jl
+++ b/test/GrpAb/Map.jl
@@ -124,4 +124,12 @@
     @test_throws ArgumentError preinverse(f)
     @test_throws ArgumentError postinverse(g)
   end
+
+  let
+    G = abelian_group([2, 2])
+    h = zero_map(G, G);
+    hh = zero_map(G, G);
+    @test h == hh
+    @test hash(h) == hash(hh)
+  end
 end
diff --git a/test/Misc/OrdLocalization.jl b/test/Misc/OrdLocalization.jl
index 9e23aa2a94..5e5a15fda8 100644
--- a/test/Misc/OrdLocalization.jl
+++ b/test/Misc/OrdLocalization.jl
@@ -1,4 +1,3 @@
-
 Qx,x = QQ["x"]
 K,a = number_field(x^6+108)
 OK = ring_of_integers(K)
@@ -124,4 +123,15 @@ end
       @test isone(L(13//13)) == true
       @test is_unit(L(50//2)) == false
     end
+
+  let
+    # hashing
+    Qx, x = QQ["x"]
+    K, a = number_field(x^6 + 108)
+    OK = ring_of_integers(K)
+    lp = prime_decomposition(OK, 5)
+    P = lp[1][1]
+    L = localization(OK, P)
+    @test hash(one(L)) == hash(one(L))
+  end
 end
diff --git a/test/RCF/rcf.jl b/test/RCF/rcf.jl
index 3eec91112b..02103ead7a 100644
--- a/test/RCF/rcf.jl
+++ b/test/RCF/rcf.jl
@@ -380,3 +380,16 @@ let
   L, = number_field(x^3 - 840539241479//13824*a^5 - 18036715089631//9216*a^4 - 18036715089631//9216*a^3 - 840539241479//13824*a^2 - 7320065966297//9216)
   @test !is_abelian(L)
 end
+
+let
+  # fix hashing
+  K, = quadratic_field(-1)
+  OK = maximal_order(K)
+  C = ray_class_field(1*OK)
+  CC = ray_class_field(1*OK)
+  @test C == CC
+  @test hash(C) == hash(CC)
+  D = Dict()
+  D[C] = 1
+  @test haskey(D, CC)
+end