PollenFiltered catamorphisms
"""
cata(f, tree, selector)
Transform nodes matching `selector` with function `f`.
"""
function
cata
(
f
,
tree
,
selector
::
Selector
)
return
cata
(
tree
)
do
x
matches
(
selector
,
x
)
?
f
(
x
)
:
x
end
end
"""
catafirst(f, tree, selector)
Like [`cate`](#), but apply `f` only to the first node that matches
`selector`.
"""
function
catafirst
(
f
,
tree
,
selector
::
Selector
)
xtree_
,
_
=
catafold
(
tree
,
false
)
do
x
,
done
(
!
done
&&
matches
(
selector
,
x
)
)
?
(
f
(
x
)
,
true
)
:
(
x
,
done
)
end
return
xtree_
endReplace
"""
replace(tree, xnode, selector)
Replace every node in `tree` that matches `selector` with `xnode`.
"""
function
replace
(
tree
,
xnode
,
selector
::
Selector
)
cata
(
x
->
xnode
,
tree
,
selector
)
end
function
replacefirst
(
tree
,
node
,
selector
::
Selector
)
return
catafirst
(
x
->
node
,
tree
,
selector
)
end
function
replacemany
(
xtree
,
xnodes
,
selector
::
Selector
)
xtree_
,
_
=
catafold
(
xtree
,
1
)
do
x
,
i
matches
(
selector
,
x
)
?
(
xnodes
[
i
]
,
i
+
1
)
:
(
x
,
i
)
end
return
xtree_
endFilter
function
Base
.
filter
(
f
,
xtree
::
Node
)
return
cata
(
xtree
)
do
x
if
x
isa
Leaf
return
x
else
return
withchildren
(
x
,
collect
(
filter
(
f
,
children
(
x
)
)
)
)
end
end
end
Base
.
filter
(
xtree
::
Node
,
sel
::
Selector
)
=
filter
(
x
->
matches
(
sel
,
x
)
,
xtree
)Insertion
abstract
type
Position
end
struct
NthChild
<:
Position
n
::
Int
selector
::
Selector
end
FirstChild
(
selector
)
=
NthChild
(
1
,
selector
)
struct
After
<:
Position
selector
::
Selector
end
struct
Before
<:
Position
selector
::
Selector
end
function
insert
(
xtree
,
x
,
pos
::
Position
)
cata
(
xtree
)
do
child
i
=
insertionindex
(
child
,
children
(
child
)
,
pos
)
if
isnothing
(
i
)
return
child
else
return
withchildren
(
child
,
_insert
(
children
(
child
)
,
i
,
x
)
)
end
end
end
function
insertfirst
(
xtree
,
x
,
pos
::
Position
)
xtree_
,
inserted
=
catafold
(
xtree
,
false
)
do
child
,
inserted
inserted
&&
return
(
child
,
inserted
)
i
=
insertionindex
(
child
,
children
(
child
)
,
pos
)
if
isnothing
(
i
)
return
child
,
false
else
return
withchildren
(
child
,
_insert
(
children
(
child
)
,
i
,
x
)
)
,
true
end
end
return
xtree_
end
function
insertionindex
(
parent
,
children
,
pos
::
NthChild
)
matches
(
pos
.
selector
,
parent
)
?
pos
.
n
:
nothing
end
function
insertionindex
(
parent
,
children
,
pos
::
Before
)
for
(
i
,
c
)
in
enumerate
(
children
)
if
matches
(
pos
.
selector
,
c
)
return
i
end
end
return
nothing
end
function
insertionindex
(
parent
,
children
,
pos
::
After
)
for
(
i
,
c
)
in
enumerate
(
children
)
if
matches
(
pos
.
selector
,
c
)
return
i
+
1
end
end
return
nothing
end
_insert
(
xs
::
AbstractVector
{
T
}
,
i
,
x
::
T
)
where
{
T
}
=
insert!
(
copy
(
xs
)
,
i
,
x
)
_insert
(
xs
::
AbstractVector
{
<:
XTree
}
,
i
,
x
::
XTree
)
=
vcat
(
xs
[
1
:
(
i
-
1
)
]
,
[
x
]
,
xs
[
i
:
end
]
)
@
testset
"
catafirst
"
begin
x
=
Node
(
:
body
,
[
Leaf
(
1
)
,
Leaf
(
2
)
]
)
x_
=
cata
(
x
,
SelectLeaf
(
)
)
do
leaf
return
Leaf
(
leaf
[
]
+
1
)
end
@
test
children
(
x_
)
[
1
]
[
]
==
2
@
test
children
(
x_
)
[
2
]
[
]
==
3
x__
=
catafirst
(
x
,
SelectLeaf
(
)
)
do
leaf
return
Leaf
(
leaf
[
]
+
1
)
end
@
test
children
(
x__
)
[
1
]
[
]
==
2
@
test
children
(
x__
)
[
2
]
[
]
==
2
end
@
testset
"
replace
"
begin
x
=
Node
(
:
body
,
[
Leaf
(
1
)
,
Leaf
(
2
)
]
)
node
=
Node
(
:
body
)
@
test
Pollen
.
replace
(
x
,
node
,
SelectNode
(
)
)
==
node
x_
=
Pollen
.
replacefirst
(
x
,
node
,
SelectLeaf
(
)
)
@
test
tag
(
x_
)
==
:
body
@
test
tag
(
children
(
x_
)
[
1
]
)
==
:
body
end
@
testset
"
insert
"
begin
x
=
Node
(
:
body
,
[
Leaf
(
1
)
,
Leaf
(
2
)
]
)
@
testset
"
NthChild
"
begin
x_
=
insert
(
x
,
Leaf
(
0
)
,
NthChild
(
1
,
SelectNode
(
)
)
)
@
test
children
(
x_
)
==
Leaf
.
(
0
:
2
)
@
test
insert
(
x
,
Leaf
(
0
)
,
NthChild
(
1
,
SelectNode
(
)
)
)
==
insertfirst
(
x
,
Leaf
(
0
)
,
NthChild
(
1
,
SelectNode
(
)
)
)
end
@
testset
"
Before
"
begin
x_
=
insert
(
x
,
Leaf
(
0
)
,
Before
(
SelectLeaf
(
)
)
)
@
test
children
(
x_
)
==
Leaf
.
(
0
:
2
)
end
@
testset
"
Before
"
begin
x_
=
insert
(
x
,
Leaf
(
0
)
,
After
(
SelectLeaf
(
)
)
)
@
test
children
(
x_
)
==
Leaf
.
(
[
1
,
0
,
2
]
)
end
end
@
testset
"
gettext
"
begin
x
=
Node
(
:
body
,
Leaf
.
(
[
"
Hello
"
,
"
"
,
"
World
"
]
)
)
@
test
Pollen
.
gettext
(
x
)
==
"
Hello World
"
end