44 lines
917 B
Go
44 lines
917 B
Go
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package funcmap
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import (
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"encoding/json"
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"fmt"
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"github.com/Knetic/govaluate"
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)
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func Math(expS string, args ...interface{}) (interface{}, error) {
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exp, err := govaluate.NewEvaluableExpressionWithFunctions(expS,
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map[string]govaluate.ExpressionFunction{
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"argv": func(arguments ...interface{}) (interface{}, error) {
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if len(arguments) != 1 {
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return nil, fmt.Errorf("argv expects 1 argument, got %d", len(arguments))
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}
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idx := int(arguments[0].(float64))
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if idx < 0 || idx > len(args) {
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return nil, fmt.Errorf("argv index out of range: %d", idx)
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}
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if idx == 0 {
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return expS, nil
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}
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vJ, err := json.Marshal(args[idx-1])
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if err != nil {
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return nil, err
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}
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var v interface{}
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if err := json.Unmarshal(vJ, &v); err != nil {
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return nil, err
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}
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return v, nil
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},
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})
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if err != nil {
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return nil, err
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}
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return exp.Evaluate(nil)
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}
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