判断一个字符串是否是时间表达式(DELPHI)

function IsTime(AString: string; ADelimiter: Char): Boolean; 

function IsValid(S: string; I: Integer): Boolean; 
begin 
case I of 
1: Result := StrToInt(S) in [0..24]; 
2, 3: Result := StrToInt(S) in [0..59]; 
else 
Result := False; 
end; //end case 
end; 
var 
P, Start: PChar; 
Str: string; 
Count: Integer; 

begin 
Result := False; 
//嘿嘿，最大长度和最小长度的区别。按照549的题意字符串长度一定在6~9 
if (not (Length(AString) in [6..8])) or (AString = '') then Exit; 
P := Pointer(AString); 
Count := 1; 
while (P^ <> #0) do 
begin 
if (Count > 3) then Exit; 
Start := P; 
while not (P^ in [#0, ADelimiter]) do Inc(P); 
SetString(Str, Start, P - Start); 
if (not IsValid(Str, Count)) then Exit; 
if (P^ = ADelimiter) then Inc(P); 
Inc(Count); 
end; 
Result := True; 
end;