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function.go
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function.go
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// Copyright 2020-2021 Dolthub, Inc.
//
// 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 function
import (
"fmt"
"strings"
"github.com/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/expression"
)
type UnaryFunc struct {
expression.UnaryExpression
// Name is the name of the function
Name string
// The type returned by the function
RetType sql.Type
}
func NewUnaryFunc(arg sql.Expression, name string, returnType sql.Type) *UnaryFunc {
return &UnaryFunc{
UnaryExpression: expression.UnaryExpression{Child: arg},
Name: name,
RetType: returnType,
}
}
// FunctionName implements sql.FunctionExpression
func (uf *UnaryFunc) FunctionName() string {
return strings.ToLower(uf.Name)
}
// EvalChild is a convenience function for safely evaluating a child expression
func (uf *UnaryFunc) EvalChild(ctx *sql.Context, row sql.Row) (interface{}, error) {
if uf.Child == nil {
return nil, nil
}
return uf.Child.Eval(ctx, row)
}
// String implements the fmt.Stringer interface.
func (uf *UnaryFunc) String() string {
return fmt.Sprintf("%s(%s)", uf.FunctionName(), uf.Child.String())
}
// Type implements the Expression interface.
func (uf *UnaryFunc) Type() sql.Type {
return uf.RetType
}