Pollen
abstract
type
XTree
end
"""
Leaf(value) <: XTree
A leaf node in an `XTree`. It holds a single value.
"""
struct
Leaf
{
T
}
<:
XTree
data
::
T
end
Base
.
getindex
(
xleaf
::
Leaf
)
=
xleaf
.
data
Leaf
(
leaf
::
Leaf
)
=
leaf
AbstractTrees
.
children
(
::
Leaf
)
=
(
)
AbstractTrees
.
printnode
(
io
::
IO
,
xleaf
::
Leaf
)
=
print
(
io
,
xleaf
[
]
)
function
AbstractTrees
.
printnode
(
io
::
IO
,
xleaf
::
Leaf
{
String
}
)
if
get
(
io
,
:
color
,
false
)
&&
!
get
(
io
,
:
compact
,
false
)
print
(
io
,
"
$
(
crayon
"
green
"
)
\"
$
(
xleaf
[
]
)
\"
$
(
crayon
"
reset
"
)
"
)
else
print
(
io
,
"
\"
$
(
xleaf
[
]
)
\"
"
)
end
end
"""
Node(tag, children...; attributes...)
A non-leaf node in an `XTree`. It has a tag, can hold a number of
children nodes and key-value attributes.
You can access and modify these using
- [`tag`](#) and [`withtag`](#)
- [`AbstractTrees.children`](#) and [`withchildren`](#)
- [`attributes`](#) and [`withattributes`](#)
## Examples
```julia
Node(:paragraph,
"I am a sentence", "This one is short";
class = "tight")
# Equivalently
Node(:paragraph,
["I am a sentence", "This one is short"],
Dict(:class => "tight"))
```
"""
Base
.
@
kwdef
struct
Node
{
T
<:
XTree
,
D
<:
Dict
{
Symbol
}
}
<:
XTree
tag
::
Symbol
children
::
Vector
{
T
}
attributes
::
D
end
Base
.
show
(
io
::
IO
,
xnode
::
Node
)
=
print_tree
(
io
,
xnode
;
maxdepth
=
4
)
function
Node
(
tag
::
Symbol
,
children
...
;
attributes
...
)
return
Node
(
tag
,
[
_xtree
(
x
)
for
x
in
children
]
,
Dict
(
pairs
(
attributes
)
)
)
end
function
Node
(
tag
::
Symbol
,
children
::
AbstractVector
{
<:
XTree
}
)
Node
(
tag
,
children
,
Dict
{
Symbol
,
Any
}
(
)
)
end
_xtree
(
node
::
Node
)
=
node
_xtree
(
leaf
::
Leaf
)
=
leaf
_xtree
(
x
)
=
Leaf
(
x
)
AbstractTrees
.
children
(
xnode
::
Node
)
=
xnode
.
children
"""
tag(node)
Get the symbol tag of a [`Node`](#).
## Examples
{cell}
```julia
using Pollen
tag(Node(:md, "hi"))
```
"""
tag
(
xnode
::
Node
)
=
xnode
.
tag
attributes
(
xnode
::
Node
)
=
xnode
.
attributes
Base
.
iterate
(
xnode
::
Node
)
=
iterate
(
children
(
xnode
)
)
Base
.
iterate
(
xnode
::
Node
,
state
)
=
iterate
(
children
(
xnode
)
,
state
)
Base
.
IteratorSize
(
::
Type
{
Node
{
T
}
}
)
where
{
T
}
=
Base
.
SizeUnknown
(
)
Base
.
eltype
(
::
Type
{
Node
{
T
}
}
)
where
{
T
}
=
T
Base
.
eltype
(
::
Type
{
<:
TreeIterator
{
<:
Node
{
T
}
}
}
)
where
{
T
}
=
T
Base
.
IteratorEltype
(
::
Type
{
<:
TreeIterator
{
<:
Node
{
T
}
}
}
)
where
{
T
}
=
Base
.
HasEltype
(
)
from AbstractTrees >= v0.4
if
isdefined
(
AbstractTrees
,
:
ChildIndexing
)
AbstractTrees
.
ChildIndexing
(
::
Type
{
<:
XTree
}
)
=
AbstractTrees
.
IndexedChildren
(
)
end
"""
withchildren(node, children)
Replace `node`'s children with `children`.
"""
withchildren
(
xnode
::
Node
,
children
)
=
Node
(
tag
(
xnode
)
,
children
,
attributes
(
xnode
)
)
"""
withtag(node, tag)
Replace the tag of `node` with `tag`.
"""
withtag
(
node
::
Node
,
tag
)
=
Node
(
tag
,
children
(
node
)
,
attributes
(
node
)
)
"""
withattributes(node, attributes)
Replace `node`'s attributes with `attributes`.
"""
withattributes
(
xnode
::
Node
,
attributes
)
=
Node
(
tag
(
xnode
)
,
children
(
xnode
)
,
attributes
)
Catamorphism
"""
catafold(f, xtree, state)
Fold a function `f : (node, state) -> (node', state')` post-order over `xtree` and
return a modified tree as well as the resulting state.
Use [`cata`](#) for a stateless catamorphism and [`fold`](#) if you don't want to
transform `xtree`.
"""
function
catafold
(
f
,
xnode
::
Node
,
state
;
T
=
XTree
)
cs
=
T
[
]
for
c
in
children
(
xnode
)
c
,
state
=
catafold
(
f
,
c
,
state
;
T
=
T
)
push!
(
cs
,
c
)
end
return
f
(
withchildren
(
xnode
,
cs
)
,
state
)
end
catafold
(
f
,
xleaf
::
Leaf
,
state
;
kwargs
...
)
=
f
(
xleaf
,
state
)
"""
cata(f, tree)
Transform every node in `tree` with function `f`.
"""
cata
(
f
,
xnode
::
Node
)
=
f
(
withchildren
(
xnode
,
XTree
[
cata
(
f
,
c
)
for
c
in
children
(
xnode
)
]
)
)
cata
(
f
,
xleaf
::
Leaf
)
=
f
(
xleaf
)
"""
fold(f, tree)
Fold over tree in post-order iteration.
## Examples
{cell}
```julia
using Pollen
node = Node(:table, Node(:row, 10, 10), Node(:row, 10, 10))
Pollen.fold(node, 0) do x, subtree
subtree isa Leaf{Int} ? x + subtree[] : x
end
```
"""
function
fold
(
f
,
tree
::
XTree
,
init
;
iterator
=
PostOrderDFS
)
foldl
(
f
,
(
l
for
l
in
iterator
(
tree
)
)
;
init
=
init
)
end
"""
fold(f, tree)
Fold over all leaves in `tree` in post-order iteration.
## Examples
```julia
node = Node(:table, Node(:row, 10, 10), Node(:row, 10, 10))
Pollen.foldleaves((x, leaf) -> x + leaf[], node, 0)
```
"""
foldleaves
(
f
,
xnode
::
XTree
,
init
)
=
foldl
(
f
,
(
l
[
]
for
l
in
Leaves
(
xnode
)
)
;
init
=
init
)
Equality comparison for
Node
s and
Leaf
s. Short-circuits on the first mismatch.
function
Base
.
:
(
==
)
(
x1
::
Node
,
x2
::
Node
)
return
(
(
tag
(
x1
)
==
tag
(
x2
)
)
&&
(
attributes
(
x1
)
==
attributes
(
x2
)
)
&&
(
length
(
children
(
x1
)
)
==
length
(
children
(
x2
)
)
)
&&
all
(
c1
==
c2
for
(
c1
,
c2
)
in
zip
(
children
(
x1
)
,
children
(
x2
)
)
)
)
end
Base
.
:
(
==
)
(
::
Node
,
_
)
=
false
Base
.
:
(
==
)
(
_
,
::
Node
)
=
false
Base
.
:
(
==
)
(
x1
::
Leaf
,
x2
::
Leaf
)
=
x1
[
]
==
x2
[
]
Base
.
:
(
==
)
(
::
Leaf
,
_
)
=
false
Base
.
:
(
==
)
(
::
Node
,
::
Leaf
)
=
false
Base
.
:
(
==
)
(
::
Leaf
,
::
Node
)
=
false
Printing
function
AbstractTrees
.
printnode
(
io
::
IO
,
x
::
Node
)
rich
=
get
(
io
,
:
color
,
false
)
&&
!
get
(
io
,
:
compact
,
false
)
print
(
io
,
"
Node(:
"
)
rich
&&
print
(
io
,
crayon
"
bold
"
)
print
(
io
,
tag
(
x
)
)
rich
&&
print
(
io
,
crayon
"
reset
"
)
if
!
isempty
(
x
.
attributes
)
print
(
io
,
"
;
"
)
rich
&&
print
(
io
,
crayon
"
dark_gray
"
)
for
(
i
,
(
key
,
value
)
)
in
enumerate
(
x
.
attributes
)
if
i
!=
1
print
(
io
,
"
,
"
)
end
print
(
io
,
key
,
"
=
"
)
show
(
io
,
value
)
end
rich
&&
print
(
io
,
crayon
"
reset
"
)
end
print
(
io
,
"
)
"
)
end
@
testset
"
XTree
"
begin
@
testset
"
Node constructors
"
begin
@
test_nowarn
Node
(
:
tag
)
@
test
tag
(
Node
(
:
tag
)
)
==
:
tag
@
test
isempty
(
children
(
Node
(
:
tag
)
)
)
@
test
isempty
(
attributes
(
Node
(
:
tag
)
)
)
@
test_nowarn
Node
(
:
tag
,
[
]
)
@
test_nowarn
Node
(
:
tag
,
Leaf
.
(
1
:
10
)
)
@
test
Node
(
:
tag
,
Leaf
.
(
1
:
10
)
)
==
Node
(
:
tag
,
(
1
:
10
)
...
)
end
@
test_nowarn
Leaf
(
1
)
@
test_nowarn
Leaf
(
Leaf
(
1
)
)
isa
Leaf
{
Int
}
@
testset
"
with*
"
begin
node
=
Node
(
:
tag
)
@
test
tag
(
withtag
(
node
,
:
gat
)
)
==
:
gat
@
test
length
(
children
(
withchildren
(
node
,
Leaf
.
(
1
:
10
)
)
)
)
==
10
@
test
attributes
(
withattributes
(
node
,
Dict
(
:
x
=>
"
hi
"
)
)
)
[
:
x
]
==
"
hi
"
end
end
@
testset
"
fold
"
begin
x
=
Node
(
:
tag
,
Leaf
.
(
1
:
10
)
)
@
test
foldleaves
(
+
,
x
,
0
)
==
sum
(
1
:
10
)
@
test
foldleaves
(
*
,
x
,
1
)
==
prod
(
1
:
10
)
x
=
Node
(
:
tag
,
"
Hello
"
,
"
World
"
)
@
test
foldleaves
(
*
,
x
,
"
"
)
==
"
HelloWorld
"
end
@
testset
"
cata
"
begin
x
=
Node
(
:
tag
,
Leaf
.
(
1
:
10
)
)
x_
=
cata
(
x
)
do
node
if
node
isa
Leaf
return
Leaf
(
-
node
[
]
)
else
return
node
end
end
@
test
x_
==
Node
(
:
tag
,
Leaf
.
(
-1
:
-1
:
-10
)
)
end
@
testset
"
catafold
"
begin
x
=
Node
(
:
tag
,
Leaf
.
(
1
:
10
)
)
x_
,
n
=
catafold
(
x
,
0
)
do
node
,
state
if
node
isa
Leaf
return
Leaf
(
-
node
[
]
)
,
state
+
1
else
return
node
,
state
end
end
@
test
x_
==
Node
(
:
tag
,
Leaf
.
(
-1
:
-1
:
-10
)
)
@
test
n
==
10
end