From 8504ed0065d7591c58cfa6ed4399bcb3c5bee462 Mon Sep 17 00:00:00 2001
From: "Viral B. Shah" <virals@gmail.com>
Date: Tue, 27 Oct 2026 17:15:43 +0000
Subject: [PATCH] Show non-default fill value in GBArray show (#104)

When the fill value differs from `defaultfill(storedeltype(A))`, print a
`fill value:` line after the GraphBLAS header. The default case is
unchanged. Doctests whose arrays have a non-default fill are updated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 docs/src/arrays.md     |  1 +
 docs/src/examples.md   |  1 +
 docs/src/index.md      |  1 +
 src/abstractgbarray.jl | 15 ++++++++++++---
 test/gbarray.jl        |  3 +++
 5 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/docs/src/arrays.md b/docs/src/arrays.md
index 614f54ac..200d1ea8 100644
--- a/docs/src/arrays.md
+++ b/docs/src/arrays.md
@@ -90,6 +90,7 @@ julia> v = GBVector{ComplexF32}(100)
 julia> v = GBMatrix(ComplexF64[1, 2im, 3 + 4im]; fill = nothing)
 3x1 GraphBLAS double complex matrix, full by col
   3 entries, memory: 288 bytes
+  fill value:  nothing
 
     (1,1)    1 + 0i
     (2,1)    0 + 2i
diff --git a/docs/src/examples.md b/docs/src/examples.md
index 9158b771..b9c2286d 100644
--- a/docs/src/examples.md
+++ b/docs/src/examples.md
@@ -46,6 +46,7 @@ julia> cohen(A), sandia(A)
 julia> bfs_parents(A, 1, 5)
 5x1 GraphBLAS int64_t matrix, bitmap by col
   5 entries, memory: 288 bytes
+  fill value:  nothing
 
     (1,1)   0
     (2,1)   1
diff --git a/docs/src/index.md b/docs/src/index.md
index ca3425e4..40130e02 100644
--- a/docs/src/index.md
+++ b/docs/src/index.md
@@ -90,6 +90,7 @@ true
 julia> B = setfill(A, missing) # no-copy alias
 1000x1000 GraphBLAS double complex matrix, hypersparse by row, ints: 32/32/32
   no entries, memory: 256 bytes
+  fill value:  missing
 
 julia> B[1, 1]
 missing
diff --git a/src/abstractgbarray.jl b/src/abstractgbarray.jl
index 776133c5..d5cf5468 100644
--- a/src/abstractgbarray.jl
+++ b/src/abstractgbarray.jl
@@ -1019,14 +1019,23 @@ function Base.setindex!(
 end
 
 function Base.show(io::IO, ::MIME"text/plain", A::AbstractGBArray) #fallback printing
-    gxbprint(io, A)
+    str = gxbstring(A)
+    fill = getfill(A)
+    if !isequal(fill, defaultfill(storedeltype(A)))
+        # insert the fill value after the two GraphBLAS header lines, or append it
+        line = "  fill value:  $fill\n"
+        i = findfirst('\n', str)
+        i = i === nothing ? nothing : findnext('\n', str, i + 1)
+        str = i === nothing ? string(chomp(str), '\n', line) : str[1:i] * line * str[i+1:end]
+    end
+    print(io, str)
 end
 
 function Base.show(io::IO, A::AbstractGBArray)
-    gxbprint(io, A)
+    show(io, MIME"text/plain"(), A)
 end
 function Base.show(io::IOContext, A::AbstractGBArray)
-    gxbprint(io, A)
+    show(io, MIME"text/plain"(), A)
 end
 
 
diff --git a/test/gbarray.jl b/test/gbarray.jl
index 5e158158..f1aeb369 100644
--- a/test/gbarray.jl
+++ b/test/gbarray.jl
@@ -35,6 +35,9 @@
             @test A'[1, 2] == 2
             deleteat!(A, 1, 1)
             @test A[1, 1] == getfill(A)
+            # #104: non-default fill shows up in show
+            @test !occursin("fill value", sprint(show, MIME"text/plain"(), A))
+            @test occursin("fill value:  17", sprint(show, MIME"text/plain"(), setfill(A, 17)))
         end
         @testset "sparse" begin
             #Construction and indexing correct for sparse matrices