ENH: @migrate macro as shorthand for @migration then migrate.

src/categorical_algebra/CSetDataStructures.jl

@@ -191,6 +191,7 @@ end
 # StructACSet Operations
 ########################
 
+Presentation(::Type{<:StructACSet{S}}) where S = Presentation(S)
 Presentation(::StructACSet{S}) where S = Presentation(S)
 
 # Accessors

src/programs/DiagrammaticPrograms.jl

@@ -5,7 +5,7 @@ string diagram or wiring diagram. DSLs for constructing wiring diagrams are
 provided by other submodules.
 """
 module DiagrammaticPrograms
-export @graph, @fincat, @finfunctor, @diagram, @migration
+export @graph, @fincat, @finfunctor, @diagram, @migrate, @migration
 
 using Base.Iterators: repeated
 using MLStyle: @match
@@ -26,7 +26,9 @@ using ...Graphs.BasicGraphs: TheoryGraph
   ename::Attr(E, Name)
 end
 
-""" Default graph type for [`@fincat`](@ref) macro and related macros.
+""" Graph with uniquely named vertices and edges.
+
+THe default graph type for the [`@fincat`](@ref) macro and related macros.
 """
 @acset_type NamedGraph(TheoryNamedGraph, index=[:src,:tgt],
                        unique_index=[:vname,:ename]) <: AbstractGraph
@@ -41,9 +43,10 @@ end
 @acset_type _MaybeNamedGraph(TheoryMaybeNamedGraph, index=[:src,:tgt],
                              unique_index=[:vname]) <: AbstractGraph
 
-""" Default graph type for [`@graph`](@ref) macro.
+""" Graph with named vertices and possibly named edges.
 
-Vertex names are uniquely indexed and edge names are optional and unindexed.
+The default graph type for the [`@graph`](@ref) macro. Vertex names are uniquely
+indexed and edge names are optional and unindexed.
 """
 const MaybeNamedGraph{Name} = _MaybeNamedGraph{Name,Union{Nothing,Name}}
 
@@ -300,14 +303,15 @@ diagram in ``C``, i.e., constructs a finitely presented indexing category ``J``
 together with a functor ``F: J → C``. This method of simultaneous definition is
 often more convenient than defining ``J`` and ``F`` separately.
 
-For example, the following diagram specifies the paths of length two in a graph:
+For example, the limit of the following diagram consists of the paths of length
+two in a graph:
 
 ```julia
 @diagram FinCat(TheoryGraph) begin
   v::V
-  (e1, e2)::E
-  (t: e1 → v)::tgt
-  (s: e2 → v)::src
+  (e₁, e₂)::E
+  (t: e₁ → v)::tgt
+  (s: e₂ → v)::src
 end
 ```
 """
@@ -373,7 +377,8 @@ end
 
 """ A diagram without a codomain category.
 
-Internal data type used by parser in [`@migration`](@ref) macro.
+An intermediate data representation used internally by the parser for the
+[`@migration`](@ref) macro.
 """
 struct DiagramData{T,ObMap,HomMap,Shape<:FinCat}
   ob_map::ObMap
@@ -392,7 +397,8 @@ Diagrams.shape(d::DiagramData) = d.shape
 
 """ A diagram morphism without a domain or codomain.
 
-Internal data type used by parser in [`@migration`](@ref) macro.
+Like [`DiagramData`](@ref), an intermediate data representation used internally
+by the parser for the [`@migration`](@ref) macro.
 """
 struct DiagramHomData{T,ObMap,HomMap}
   ob_map::ObMap
@@ -403,10 +409,21 @@ struct DiagramHomData{T,ObMap,HomMap}
   end
 end
 
-""" Define a data migration query.
+""" Contravariantly migrate data from one acset to another.
+"""
+macro migrate(tgt_type, src_acset, body)
+  quote
+    let T = $(esc(tgt_type)), X = $(esc(src_acset))
+      migrate(T, X, parse_migration(Presentation(T), Presentation(X),
+                                    $(Meta.quot(body))))
+    end
+  end
+end
+
+""" Define a contravariant data migration.
 
-This macro provides a DSL to specify a data migration query from a ``C``-set to
-a ``D``-set for arbitrary schemas ``C`` and ``D``.
+This macro provides a DSL to specify a contravariant data migration from
+``C``-sets to ``D``-sets for given schemas ``C`` and ``D``.
 """
 macro migration(src_schema, body)
   :(parse_migration($(esc(src_schema)), $(Meta.quot(body))))

src/theories/Schema.jl

@@ -176,7 +176,7 @@ function SchemaDescTypeType(s::SchemaDesc)
   }
 end
 
-function Presentation(S::Type{T}) where T <: SchemaDescType
+function Presentation(::Type{S}) where S <: SchemaDescType
   pres = Presentation(FreeSchema)
 
   obs = map(x -> Ob(FreeSchema, x), collect(ob(S)))

test/categorical_algebra/DataMigrations.jl

@@ -3,8 +3,7 @@ using Test
 
 using Catlab, Catlab.Theories, Catlab.Graphs, Catlab.CategoricalAlgebra
 using Catlab.Programs.DiagrammaticPrograms
-using Catlab.Graphs.BasicGraphs: TheoryGraph, TheoryReflexiveGraph,
-  TheorySymmetricGraph, TheorySymmetricReflexiveGraph, TheoryWeightedGraph
+using Catlab.Graphs.BasicGraphs: TheoryGraph, TheoryWeightedGraph
 using Catlab.Graphs.BipartiteGraphs: TheoryUndirectedBipartiteGraph
 
 # Contravariant migration
@@ -129,7 +128,8 @@ migrate!(h, g, F)
 @test sort!(collect(zip(h[:src], h[:tgt]))) == [(6,8), (7,9), (8,10)]
 
 # Graph whose vertices are paths of length 2 and edges are paths of length 3.
-F = @migration TheoryGraph TheoryGraph begin
+g = path_graph(Graph, 6)
+h = @migrate Graph g begin
   V => @join begin
     v::V
     (e₁, e₂)::E
@@ -147,39 +147,36 @@ F = @migration TheoryGraph TheoryGraph begin
   src => (v => v₁; e₁ => e₁; e₂ => e₂; t => t₁; s => s₁)
   tgt => (v => v₂; e₁ => e₂; e₂ => e₃; t => t₂; s => s₂)
 end
-g = path_graph(Graph, 6)
-h = migrate(Graph, g, F)
 @test h == path_graph(Graph, 4)
 
 # Gluing migration
 #-----------------
 
 # Free reflexive graph on a graph.
-F = @migration TheoryReflexiveGraph TheoryGraph begin
+g = cycle_graph(Graph, 5)
+h = @migrate ReflexiveGraph g begin
   V => V
   E => @cases (v::V; e::E)
   src => (e => src)
   tgt => (e => tgt)
   refl => v
 end
-g = cycle_graph(Graph, 5)
-h = migrate(ReflexiveGraph, g, F)
 @test h == cycle_graph(ReflexiveGraph, 5)
 
 # Free symmetric graph on a graph.
-F = @migration TheorySymmetricGraph TheoryGraph begin
+g = star_graph(Graph, 5)
+h = @migrate SymmetricGraph g begin
   V => V
   E => @cases (fwd::E; rev::E)
   src => (fwd => src; rev => tgt)
   tgt => (fwd => tgt; rev => src)
   inv => (fwd => rev; rev => fwd)
 end
-g = star_graph(Graph, 5)
-h = migrate(SymmetricGraph, g, F)
 @test is_isomorphic(h, star_graph(SymmetricGraph, 5))
 
 # Free symmetric reflexive graph on a reflexive graph.
-F = @migration TheorySymmetricReflexiveGraph TheoryReflexiveGraph begin
+g = star_graph(ReflexiveGraph, 5)
+h = @migrate SymmetricReflexiveGraph g begin
   V => V
   E => @glue begin
     (fwd, rev)::E
@@ -195,15 +192,14 @@ F = @migration TheorySymmetricReflexiveGraph TheoryReflexiveGraph begin
     refl_fwd => refl_rev; refl_rev => refl_fwd
   end
 end
-g = star_graph(ReflexiveGraph, 5)
-h = migrate(SymmetricReflexiveGraph, g, F)
 @test is_isomorphic(h, star_graph(SymmetricReflexiveGraph, 5))
 
 # Gluc migration
 #---------------
 
 # Graph with edges that are paths of length <= 2.
-F = @migration TheoryGraph TheoryGraph begin
+g = path_graph(Graph, 4)
+h = @migrate Graph g begin
   V => V
   E => @cases begin
     v => V
@@ -218,8 +214,6 @@ F = @migration TheoryGraph TheoryGraph begin
   src => (e => src; path => e₁⋅src)
   tgt => (e => tgt; path => e₂⋅tgt)
 end
-g = path_graph(Graph, 4)
-h = migrate(Graph, g, F)
 h′ = @acset Graph begin
   V = 4
   E = 9