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46 lines
988 B
Go
46 lines
988 B
Go
package eval
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import (
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"errors"
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"strings"
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"github.com/antonmedv/expr"
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"github.com/antonmedv/expr/ast"
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)
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// AST Visitor that changes Integer to Float
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type patcher struct{}
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func (p *patcher) Enter(_ *ast.Node) {}
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func (p *patcher) Exit(node *ast.Node) {
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n, ok := (*node).(*ast.IntegerNode)
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if ok {
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ast.Patch(node, &ast.FloatNode{Value: float64(n.Value)})
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}
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}
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// EvaluateExpressionToFloat64 evaulates a simple math expression string to a float64
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func EvaluateExpressionToFloat64(input string, env interface{}) (float64, error) {
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input = strings.TrimSpace(input)
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if input == "" {
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return 0, nil
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}
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program, err := expr.Compile(input, expr.Env(env), expr.Patch(&patcher{}))
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if err != nil {
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return 0, err
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}
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result, err := expr.Run(program, env)
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if err != nil {
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return 0, err
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}
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f64, ok := result.(float64)
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if !ok {
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ival, ok := result.(int)
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if !ok {
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return 0, errors.New("expression did not return numeric type")
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}
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f64 = float64(ival)
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}
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return f64, nil
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}
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