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sum_array.go

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package optimizer

import (

"fmt"

. "github.com/expr-lang/expr/ast"

)

type sumArray struct{}

func (*sumArray) Visit(node *Node) {

if sumBuiltin, ok := (*node).(*BuiltinNode); ok &&

sumBuiltin.Name == "sum" &&

len(sumBuiltin.Arguments) == 1 {

if array, ok := sumBuiltin.Arguments[0].(*ArrayNode); ok &&

len(array.Nodes) >= 2 {

patchCopyType(node, sumArrayFold(array))

}

}

}

func sumArrayFold(array *ArrayNode) *BinaryNode {

if len(array.Nodes) > 2 {

return &BinaryNode{

Operator: "+",

Left: array.Nodes[0],

Right: sumArrayFold(&ArrayNode{Nodes: array.Nodes[1:]}),

}

} else if len(array.Nodes) == 2 {

return &BinaryNode{

Operator: "+",

Left: array.Nodes[0],

Right: array.Nodes[1],

}

}

panic(fmt.Errorf("sumArrayFold: invalid array length %d", len(array.Nodes)))

}