also delete(filter)

src/functionlenses.jl

@@ -79,10 +79,14 @@ end
 
 
 set(obj, o::Base.Fix1{typeof(map)}, val) = map((ob, v) -> set(ob, o.x, v), obj, val)
+
 set(obj, o::Base.Fix1{typeof(filter)}, val) = @set obj[findall(o.x, obj)] = val
 modify(f, obj, o::Base.Fix1{typeof(filter)}) = @modify(f, obj[findall(o.x, obj)])
+delete(obj, o::Base.Fix1{typeof(filter)}) = filter(!o.x, obj)
+
 set(obj, o::typeof(skipmissing), val) = @set obj |> filter(!ismissing, _) = collect(val)
 modify(f, obj, o::typeof(skipmissing)) = @modify(f, obj |> filter(!ismissing, _))
+
 set(obj, ::typeof(sort), val) = @set obj[sortperm(obj)] = val
 modify(f, obj, ::typeof(sort)) = @modify(f, obj[sortperm(obj)])
 

src/optics.jl

@@ -279,6 +279,9 @@ function modify(f, obj, w::If)
     end
 end
 
+# it doesn't seem possible to support delete(If) for collections
+delete(obj, o::If) = error("`delete(obj, ::If)` not supported, try using `filter` as an optic instead")
+
 """
     mapproperties(f, obj)
 

test/test_delete.jl

@@ -29,6 +29,9 @@ using StaticArrays
             @test_throws BoundsError delete(A, @optic(_[10]))
             @test delete(A, @optic(_[end])) == [1, 2]
             @test A == [1, 2, 3]  # not changed
+
+            @test_throws "not supported" delete(A, @optic _ |> Elements() |> If(isodd))
+            @test delete(A, @optic filter(isodd, _)) == [2]
         end
         let A = Dict("a" => 1, "b" => 2, "c" => 3)
             @test delete(A, @optic(_["a"])) == Dict("b" => 2, "c" => 3)