42 lines
644 B
Go
42 lines
644 B
Go
package main
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import (
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"fmt"
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"io"
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"log"
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"os"
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)
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type numberOfArgumentError struct {
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length int
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}
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func (e numberOfArgumentError) Error() string {
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return fmt.Sprintf("unexpected number of arguments passed to the greeter: want 0 or 1 argument, got %d", e.length)
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}
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func main() {
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osArgs := os.Args[1:]
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if err := greet(os.Stdout, osArgs); err != nil {
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log.Fatalf("ERROR: %s.\n", err)
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}
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}
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func greet(w io.Writer, n []string) error {
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var name string
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if len(n) > 1 {
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return numberOfArgumentError{length: len(n)}
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}
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if len(n) == 0 {
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name = "World"
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} else {
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name = n[0]
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}
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fmt.Fprintf(w, "Hello, %s!\n", name)
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return nil
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}
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