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permutation.go
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permutation.go
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package astpatt
import (
"github.com/tehsphinx/astrav"
)
// permutations creates a bunch of possible pattern permutations with the same meaning.
func permutations(ast astrav.Node) []Node {
childPermuts := permutChildren(ast)
childCombis := combinations(childPermuts)
var nodes []Node
if len(childCombis) == 0 {
node := createNode(ast.NodeType())
node.fillNode(nil, ast)
nodes = append(nodes, node)
}
for _, perm := range childCombis {
permutations := permuteNodes(perm, ast)
for _, p := range permutations {
permNode := createNode(ast.NodeType())
permNode.fillNode(p, ast)
nodes = append(nodes, permNode)
}
}
return nodes
}
func permutChildren(ast astrav.Node) [][]Node {
var childPermuts [][]Node
for _, child := range ast.Children() {
var (
children []Node
nn = createNode(child.NodeType())
)
if nn.isType(NodeTypeOmit) {
continue
}
if nn.isType(NodeTypeSkip) {
chPerms := permutChildren(child)
childPermuts = append(childPermuts, chPerms...)
continue
} else {
children = permutations(child)
}
childPermuts = append(childPermuts, children)
}
return childPermuts
}
func permuteNodes(nodes []Node, parentAST astrav.Node) [][]Node {
var perms [][]Node
if parentAST.NodeType() == astrav.NodeTypeFile {
perms = Perm(nodes)
} else {
perms = append(perms, nodes)
}
return perms
}
func combinations(pNodes [][]Node) (combinations [][]Node) {
comb := func(input []Node, prev [][]Node) (output [][]Node) {
if len(prev) == 0 {
prev = append(prev, []Node{})
}
for _, node := range input {
for _, prevNode := range prev {
output = append(output, append(prevNode, node))
}
}
return output
}
for _, nodes := range pNodes {
combinations = comb(nodes, combinations)
}
return combinations
}
// Perm calls f with each permutation of a.
func Perm(nodes []Node) [][]Node {
return perm(nodes, nil, 0)
}
// Permute the values at index i to len(a)-1.
func perm(a []Node, nodes [][]Node, i int) [][]Node {
if i > len(a) {
var b []Node
return append(nodes, append(b, a...))
}
nodes = perm(a, nodes, i+1)
for j := i + 1; j < len(a); j++ {
a[i], a[j] = a[j], a[i]
nodes = perm(a, nodes, i+1)
a[i], a[j] = a[j], a[i]
}
return nodes
}