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range.go
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range.go
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package dynaml
import (
"fmt"
"github.com/mandelsoft/spiff/yaml"
)
type RangeExpr struct {
Start Expression
End Expression
}
func (e RangeExpr) getRange(binding Binding, size int) (int64, int64, EvaluationInfo, bool, bool) {
resolved := true
info := EvaluationInfo{}
if size < 0 && (e.Start == nil || e.End == nil) {
info.SetError("range expression requires start and end index")
return 0, 0, info, false, resolved
}
range_start := int64(0)
range_end := int64(size - 1)
if e.Start != nil {
val, info, ok := ResolveIntegerExpressionOrPushEvaluation(&e.Start, &resolved, &info, binding, false)
if !ok {
return 0, 0, info, false, resolved
}
range_start = val
if val < 0 && e.End == nil {
range_end = -1
}
}
if e.End != nil {
val, info, ok := ResolveIntegerExpressionOrPushEvaluation(&e.End, &resolved, &info, binding, false)
if !ok {
return 0, 0, info, false, resolved
}
range_end = val
if val < 0 && e.Start == nil {
range_start = -int64(size)
}
}
if e.Start == nil && e.End == nil {
info.SetError("slice operator requires start or end index")
return 0, 0, info, false, resolved
}
return range_start, range_end, info, true, resolved
}
func (e RangeExpr) Evaluate(binding Binding, locally bool) (interface{}, EvaluationInfo, bool) {
start, end, info, ok, resolved := e.getRange(binding, -1)
if !ok {
return nil, info, false
}
if !resolved {
return e, info, true
}
nodes := []yaml.Node{}
delta := int64(1)
if start > end {
delta = -1
}
for i := start; i*delta <= end*delta; i += delta {
nodes = append(nodes, NewNode(i, binding))
}
return nodes, info, true
}
func (e RangeExpr) String() string {
return fmt.Sprintf("[%s..%s]", e.Start, e.End)
}