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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package examples
import (
"fmt"
"log"
"github.com/google/cel-go/cel"
"github.com/google/cel-go/common/types"
"github.com/google/cel-go/common/types/ref"
)
func ExampleCustomGlobalFunction() {
env, err := cel.NewEnv(
cel.Variable("i", cel.StringType),
cel.Variable("you", cel.StringType),
cel.Function("shake_hands",
cel.Overload("shake_hands_string_string",
[]*cel.Type{cel.StringType, cel.StringType},
cel.StringType,
cel.BinaryBinding(func(lhs, rhs ref.Val) ref.Val {
return types.String(
fmt.Sprintf("%s and %s are shaking hands.\n", lhs, rhs))
},
),
),
),
)
if err != nil {
log.Fatalf("environment creation error: %v\n", err)
}
// Check iss for error in both Parse and Check.
ast, iss := env.Compile(`shake_hands(i,you)`)
if iss.Err() != nil {
log.Fatalln(iss.Err())
}
prg, err := env.Program(ast)
if err != nil {
log.Fatalf("Program creation error: %v\n", err)
}
out, _, err := prg.Eval(map[string]any{
"i": "CEL",
"you": "world",
})
if err != nil {
log.Fatalf("Evaluation error: %v\n", err)
}
fmt.Println(out)
// Output:CEL and world are shaking hands.
}
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