From e90d438623fbcf6df379d6e87bfa4b714cb0e9fb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sat, 2 May 2026 20:22:26 +0200
Subject: [PATCH] Implements implicit_basis for SemisimpleBasis

---
 src/fixed.jl  | 16 ++++++++++++++++
 test/fixed.jl |  6 ++++++
 2 files changed, 22 insertions(+)

diff --git a/src/fixed.jl b/src/fixed.jl
index 123eea3..dd1895b 100644
--- a/src/fixed.jl
+++ b/src/fixed.jl
@@ -15,6 +15,15 @@ Base.getindex(b::SimpleBasis, i::Integer) = b.elements[i]
 Base.iterate(b::SimpleBasis) = iterate(b.elements)
 Base.iterate(b::SimpleBasis, st) = iterate(b.elements, st)
 
+function MA.promote_operation(
+    ::typeof(implicit_basis),
+    ::Type{<:SimpleBasis{T}},
+) where {T}
+    return MA.promote_operation(SA.basis, T)
+end
+
+implicit_basis(basis::SimpleBasis) = SA.basis(first(basis.elements))
+
 """
     struct SemisimpleElement{P}
         elements::Vector{P}
@@ -59,6 +68,13 @@ struct SemisimpleBasis{T,B<:SA.ExplicitBasis{T}} <:
     bases::Vector{B}
 end
 
+function MA.promote_operation(
+    ::typeof(implicit_basis),
+    ::Type{<:SemisimpleBasis{T,B}},
+) where {T,B}
+    return MA.promote_operation(implicit_basis, B)
+end
+
 Base.length(b::SemisimpleBasis) = length(first(b.bases))
 
 function _iterate(b::SemisimpleBasis, elem_state)
diff --git a/test/fixed.jl b/test/fixed.jl
index c21594f..4c2dc47 100644
--- a/test/fixed.jl
+++ b/test/fixed.jl
@@ -22,6 +22,9 @@ end
 
     sb = MB.SimpleBasis([ae1, ae2, ae3])
 
+    @test MA.promote_operation(MB.implicit_basis, typeof(sb)) ==
+          typeof(MB.implicit_basis(sb))
+
     @testset "length" begin
         @test length(sb) == 3
     end
@@ -120,6 +123,9 @@ end
         sb = MB.SimpleBasis([ae1, ae2, ae3])
         semi = MB.SemisimpleBasis([sb])
 
+        @test MA.promote_operation(MB.implicit_basis, typeof(semi)) ==
+              typeof(MB.implicit_basis(semi))
+
         @test length(semi) == 3
         @test length(semi.bases) == 1