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i.go
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i.go
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package maybe
import "fmt"
// I implements the Maybe monad for a int. An I is considered 'valid' or
// 'invalid' depending on whether it contains a int or an error value.
type I struct {
just int
err error
}
// NewI constructs an I from a given int or error. If e is not nil, returns
// ErrI(e), otherwise returns JustI(s)
func NewI(s int, e error) I {
if e != nil {
return ErrI(e)
}
return JustI(s)
}
// JustI constructs a valid I from a given int.
func JustI(s int) I {
return I{just: s}
}
// ErrI constructs an invalid I from a given error.
func ErrI(e error) I {
return I{err: e}
}
// IsErr returns true for an invalid I.
func (m I) IsErr() bool {
return m.err != nil
}
// Bind applies a function that takes a int and returns an I.
func (m I) Bind(f func(s int) I) I {
if m.err != nil {
return m
}
return f(m.just)
}
// Split applies a function that takes a int and returns an AoI.
func (m I) Split(f func(s int) AoI) AoI {
if m.err != nil {
return ErrAoI(m.err)
}
return f(m.just)
}
// String returns a string representation, mostly useful for debugging.
func (m I) String() string {
if m.err != nil {
return fmt.Sprintf("Err %v", m.err)
}
return fmt.Sprintf("Just %v", m.just)
}
// ToStr applies a function that takes an int and returns an S.
func (m I) ToStr(f func(x int) S) S {
if m.err != nil {
return ErrS(m.err)
}
return f(m.just)
}
// Unbox returns the underlying int value or error.
func (m I) Unbox() (int, error) {
return m.just, m.err
}