Creating Single-Entry Matrix?

General Usage
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4

FillArrays has a OneElement type that provides a non-materialized implementation:

julia> OneElement(1 #= value =#, (2,2) #= index =#, (3,3) #= size =#)
3×3 OneElement{Int64, 2, Tuple{Int64, Int64}, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}:
 ⋅  ⋅  ⋅
 ⋅  1  ⋅
 ⋅  ⋅  ⋅

If you want a matrix from this, you may convert it:

julia> A = OneElement(1, (2,2), (3,3));

julia> Matrix(A)
3×3 Matrix{Int64}:
 0  0  0
 0  1  0
 0  0  0
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