2、=t+1; s[t]:=x; end;function pop:integer;{出栈} begin pop:=s[t]; t:=t-1; end;begin readln(a); {读入后缀表达式} len:=length(a); i:=1; {后缀表达式字符指针初始化} t:=0; {栈初始化} while i<=len do {处理后缀表达式,直至结束} begin case a[i] of'0'..'9':begin k:=
3、0; while a[i]<>’.’ do begin {从s中取出一个完整的操作数k} k:=10*k+ord(a[i])-48; i:=i+1; end; push(k);{把k压栈} end; '+':push(pop+pop); {从栈s中取出栈顶