delphi7 怎么判断输入的字符串是一个实数（包括指数和小数），请求高手帮忙_Delphi

delphi7 如何判断输入的字符串是一个实数（包括指数和小数），请求高手帮忙
内容如题...
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可以利用类型转换函数，-1代表一个不可能出现的值
Result := StrToFloatDef(XXX, -1) <> -1;
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function   StrToFloat(const   S:   string):   Extended;

Description:
  Use   StrToFloat   to   convert   astring,   S,   to   a   floating-point   value.   S   must   consist   of   an   optional   sign   (+   or   -),   a   string   of   digits   with   an   optional   decimal   point,   and   an   optional   mantissa.   The   mantissa   consists   of   'E'   or   'e'   followed   by   an   optional   sign   (+   or   -)   and   a   whole   number.   Leading   and   trailing   blanks   are   ignored.
  The   DecimalSeparator   global   variable   defines   the   character   that   must   be   used   as   a   decimal   point.   Thousand   separators   and   currency   symbols   are   not   allowed   in   the   string.   If   S   doesn't   contain   a   valid   value,   StrToFloat   raises   an   EConvertError   exception.
//if there is a exception, the string isn't a float or double
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typeof()
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顶下，不懂，呵呵！
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引用:

function StrToFloat(const S: string): Extended;

Description:
  Use StrToFloat to convert astring, S, to a floating-point value. S must consist of an optional sign (+ or -), a string of digi……

麻烦写个实际代码？？
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使用正则表达式！可以帮你解决这个问题

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不明白。。
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