Merge pull request #86 from tpgillam/tg/zap_until

Implement zap_until

Project.toml

@@ -1,7 +1,7 @@
 name = "TimeDag"
 uuid = "91963e24-6e66-4132-aeb8-436d9f37dbc7"
 authors = ["Invenia Technical Computing Corporation", "Tom Gillam <[email protected]>"]
-version = "0.1.23"
+version = "0.1.24"
 
 [deps]
 AbstractTrees = "1520ce14-60c1-5f80-bbc7-55ef81b5835c"

docs/src/reference/misc_ops.md

@@ -18,6 +18,7 @@ Base.rand
 ```@docs
 Base.filter
 Base.skipmissing
+zap_until
 ```
 
 ## Type conversion

src/TimeDag.jl

@@ -27,6 +27,8 @@ export block_node, constant, empty_node, iterdates, pulse, tea_file
 # Alignment nodes.
 export active_count, align, align_once, coalign, count_knots, first_knot, lag, right, left
 export prepend, throttle
+# Conditional nodes.
+export zap_until
 # Type conversion
 export convert_value
 # Other nodes

src/ops/conditional.jl

@@ -48,3 +48,21 @@ function Base.skipmissing(x::Node)
     _is_empty(x) && return empty_node(T)
     return obtain_node((x,), SkipMissing{T}())
 end
+
+# TODO a more efficient implementation for this would simply slice blocks as required,
+#   rather than evaluate the condition knotwise.
+struct ZapUntil{T} <: UnaryNodeOp{T}
+    time::DateTime
+end
+stateless_operator(::ZapUntil) = true
+operator!(op::ZapUntil{T}, t::DateTime, x) where {T} = t < op.time ? Maybe{T}() : Maybe(x)
+
+"""
+    zap_until(x::Node, t) -> Node
+
+Given a node `x`, return a node in which all knots strictly before `t` are omitted.
+"""
+function zap_until(x::Node{T}, t::DateTime) where {T}
+    _is_empty(x) && return x
+    return obtain_node((x,), ZapUntil{T}(t))
+end

test/ops/conditional.jl

@@ -56,4 +56,26 @@ end
     ])
 end
 
+@testset "zap_until" begin
+    n = empty_node(Int64)
+    @test zap_until(n, DateTime(2000)) === n
+
+    @test _eval(zap_until(n1, DateTime(2000, 1, 3))) ==
+        Block([
+            DateTime(2000, 1, 3) => 3,
+            DateTime(2000, 1, 4) => 4
+        ])
+
+    @test _eval(zap_until(n_boolean, DateTime(2000, 1, 3))) ==
+        Block([
+            DateTime(2000, 1, 3) => true,
+            DateTime(2000, 1, 4) => true
+        ])
+
+    for cutoff in first(b4.times):Minute(133):last(b4.times)
+        @test _eval(zap_until(n4, cutoff)) ==
+            TimeDag._slice(b4, cutoff, last(b4.times) + Hour(1))
+    end
+end
+
 #! format: on