c++表达式求值实现.doc

1：工程结构2：源代码1. cpp:#include#include#include#includeusing namespace std;typedef float type1;typedef char type2;struct zhan1type1 opnd50;int basic;int top;struct zhan2type2 optr52;int basic;int top;char yunsuan8=+,-,*,/,(,),#;int priority77= 3,3,1,1,1,3,3,3,3,1,1,1,3,3,3,3,3,3,1,1,3,3,3,3,3,1,3,3,1,1,1,1,1,2,0,3,3,3,3,0,3,3,1,1,1,1,1,0,2 ;int yunsuanfu(char c)for(int i=0;i7;i+)if(c=yunsuani)return 1;return 0;int youxianji(char a,char b)int ia=0;int ib=0;for(int i=0;i7;i+)if(a=yunsuani)ia=i;break;for(i=0;i7;i+)if(b=yunsuani)ib=i;break;return priorityiaib;int operate(int a,char the,int b)char s5=+,-,*,/;if(the=s0) return a+b;if(the=s1) return a-b;if(the=s2) return a*b;if(the=s3) return a/b;void main()zhan1 s1;zhan2 s2;s1.top=0;s1.basic=0;s2.top=0;s2.basic=0; s1.opnds1.top=0;char c;s2.optrs2.top=#;c=getchar();while(c!=#|s2.optrs2.top!=#)if(yunsuanfu(c)switch(youxianji(s2.optrs2.top,c)case 0:cout输入操作符错误，重新输入：endl;c=getchar();break;case 1:s2.top+;s2.optrs2.top=c;c=getchar();break;case 2:s2.top-;c=getchar();break;case 3:char theta=s2.optrs2.top;s2.top-;float b=s1.opnds1.top-1;s1.top-;float a=s1.opnds1.top-1;s1.top-;float answer=operate(a,theta,b);s1.opnds1.top=answer;s1.top+;break;else if(isdigit(c) float shuzi12; int i=0; double s=0.0; float zhi=0; shuzii=(float)c-48.0; i+; c=getchar(); while(isdigit(c)&i=11) shuzii=(float)c-48.0; i+; c=getchar(); s=i; for(int j=0;ji;j+) float m=pow(10.0,s-1.0); zhi=zhi+m*shuzij; s-; s1.opnds1.top=zhi; s1.top+; if(!isdigit(c)&!y