yq/pkg/yqlib/operator_reduce.go

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package yqlib
import (
"container/list"
"fmt"
)
func reduceOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
log.Debugf("-- reduceOp")
//.a as $var reduce (0; . + $var)
//lhs is the assignment operator
//rhs is the reduce block
// '.' refers to the current accumulator, initialised to 0
// $var references a single element from the .a
//ensure lhs is actually an assignment
//and rhs is a block (empty)
if expressionNode.LHS.Operation.OperationType != assignVariableOpType {
return Context{}, fmt.Errorf("reduce must be given a variables assignment, got %v instead", expressionNode.LHS.Operation.OperationType.Type)
} else if expressionNode.RHS.Operation.OperationType != blockOpType {
return Context{}, fmt.Errorf("reduce must be given a block, got %v instead", expressionNode.RHS.Operation.OperationType.Type)
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}
arrayExpNode := expressionNode.LHS.LHS
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array, err := d.GetMatchingNodes(context, arrayExpNode)
if err != nil {
return Context{}, err
}
variableName := expressionNode.LHS.RHS.Operation.StringValue
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initExp := expressionNode.RHS.LHS
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accum, err := d.GetMatchingNodes(context, initExp)
if err != nil {
return Context{}, err
}
log.Debugf("with variable %v", variableName)
blockExp := expressionNode.RHS.RHS
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for el := array.MatchingNodes.Front(); el != nil; el = el.Next() {
candidate := el.Value.(*CandidateNode)
log.Debugf("REDUCING WITH %v", NodeToString(candidate))
l := list.New()
l.PushBack(candidate)
accum.SetVariable(variableName, l)
accum, err = d.GetMatchingNodes(accum, blockExp)
if err != nil {
return Context{}, err
}
}
return accum, nil
}