问题：编写一个Lex程序以计算正数，负数和分数
解释 ：
FLEX(快速词法分析器生成器)是一种工具/计算机程序，用于生成Vern Paxson于1987年左右在C中编写的词法分析器(扫描器或词法分析器)。Lex读取指定词法分析器的输入流，并输出在C语言中实现词法分析器的源代码编程语言。函数yylex()是运行规则部分的主要flex函数。
先决条件： Flex(快速词法分析器生成器)
例子：
Input: 2 -8 -2.5 8.5
Output: No. of positive numbers: 1
No. of Negative numbers: 1
No. of Positive numbers in fractions: 1
No. of Negative numbers in fractions: 1
Input: 1 2 3 -4 -5 6.5 7.5
Output: No. of positive numbers: 3
No. of Negative numbers: 2
No. of Positive numbers in fractions: 2
No. of Negative numbers in fractions: 0 执行：
/* Lex program to Count the Positive numbers,
- Negative numbers and Fractions */
%{
/* Definition section */
int postiveno=0;
int negtiveno=0;
int positivefractions=0;
int negativefractions=0;
%}
/* Rule Section */
DIGIT [0-9]
%%
\+?{DIGIT}+ postiveno++;
-{DIGIT}+ negtiveno++;
\+?{DIGIT}*\.{DIGIT}+ positivefractions++;
-{DIGIT}*\.{DIGIT}+ negativefractions++;
. ;
%%
// driver code
int main()
{
yylex();
printf("\nNo. of positive numbers: %d", postiveno);
printf("\nNo. of Negative numbers: %d", negtiveno);
printf("\nNo. of Positive numbers in fractions: %d", positivefractions);
printf("\nNo. of Negative numbers in fractions: %d\n", negativefractions);
return 0;
}
输出：
