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| type State int
type CharType int
const (
STATE_INITIAL State = iota
STATE_INT_SIGN
STATE_INTEGER
STATE_POINT
STATE_POINT_WITHOUT_INT
STATE_FRACTION
STATE_EXP
STATE_EXP_SIGN
STATE_EXP_NUMBER
STATE_END
)
const (
CHAR_NUMBER CharType = iota
CHAR_EXP
CHAR_POINT
CHAR_SIGN
CHAR_SPACE
CHAR_ILLEGAL
)
func toCharType(ch byte) CharType {
switch ch {
case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
return CHAR_NUMBER
case 'e', 'E':
return CHAR_EXP
case '.':
return CHAR_POINT
case '+', '-':
return CHAR_SIGN
case ' ':
return CHAR_SPACE
default:
return CHAR_ILLEGAL
}
}
func isNumber(s string) bool {
transfer := map[State]map[CharType] State{
STATE_INITIAL: map[CharType] State{
CHAR_SPACE: STATE_INITIAL,
CHAR_NUMBER: STATE_INTEGER,
CHAR_POINT: STATE_POINT_WITHOUT_INT,
CHAR_SIGN: STATE_INT_SIGN,
},
STATE_INT_SIGN: map[CharType] State{
CHAR_NUMBER: STATE_INTEGER,
CHAR_POINT: STATE_POINT_WITHOUT_INT,
},
STATE_INTEGER: map[CharType] State{
CHAR_NUMBER: STATE_INTEGER,
CHAR_EXP: STATE_EXP,
CHAR_POINT: STATE_POINT,
CHAR_SPACE: STATE_END,
},
STATE_POINT: map[CharType] State{
CHAR_NUMBER: STATE_FRACTION,
CHAR_EXP: STATE_EXP,
CHAR_SPACE: STATE_END,
},
STATE_POINT_WITHOUT_INT: map[CharType] State{
CHAR_NUMBER: STATE_FRACTION,
},
STATE_FRACTION: map[CharType] State{
CHAR_NUMBER: STATE_FRACTION,
CHAR_EXP: STATE_EXP,
CHAR_SPACE: STATE_END,
},
STATE_EXP: map[CharType] State{
CHAR_NUMBER: STATE_EXP_NUMBER,
CHAR_SIGN: STATE_EXP_SIGN,
},
STATE_EXP_SIGN: map[CharType] State{
CHAR_NUMBER: STATE_EXP_NUMBER,
},
STATE_EXP_NUMBER: map[CharType] State{
CHAR_NUMBER: STATE_EXP_NUMBER,
CHAR_SPACE: STATE_END,
},
STATE_END: map[CharType] State{
CHAR_SPACE: STATE_END,
},
}
state := STATE_INITIAL
for i := 0; i < len(s); i++ {
typ := toCharType (s [i])
if _, ok := transfer [state][typ]; !ok {
return false
} else {
state = transfer [state][typ]
}
}
return state == STATE_INTEGER || state == STATE_POINT || state == STATE_FRACTION || state == STATE_EXP_NUMBER || state == STATE_END
}
|
