atof

本篇博客用于记录我自己用C++实现的一个计算器，目标是完成加减乘除带括号的四则运算，并在后期用工厂设计模式加以优化。 Part 1：calculate 1+1=2 实现这样的一个式子的计算，只需要用到字符串分割即可，一开始尝试了stringstream去先读入一整个字符串"1+2",然后创建了两个临时变量int和一个char，用>>去读入，但是发现读入的char放在中间被忽略掉了 string s ="12+34"; // stringstream ss(s); // int n1,n2,c; // ss>>n1>>c>>n2;//c is 34 ,the '+' is ignored 然后我就换用了substr去进行分割，substr有两个参数，一个是开始分出字串的位置，另一个是字串的长度，第二个参数默认值是npos，也就是字符串末尾。 int i =0; while(isdigit(s[i])) { ++i;//pos } // int n =atof("22.0"); // cout<<n; //float d = atof(s.substr(0,i).c_str()); cout<<cal( atof(s.substr(0,i).c_str()) , atof(s.substr(i+1).c_str()) ,s[i])<<endl;　　　　//string to const

I can't understand the following atoi implementation code, specifically this line: k = (k << 3) + (k << 1) + (*p) - '0'; Here is the code: int my_atoi(char *p) { int k = 0; while (*p) { k = (k << 3) + (k << 1) + (*p) - '0'; p++; } return k; } Can someone explain it to me ? Another question: what should be the algorithm of atof implementation ? R.. k = (k << 3) + (k << 1); means k = k * 2³ + k * 2¹ = k * 8 + k * 2 = k * 10 Does that help? The *p - '0' term adds the value of the next digit; this works because C requires that the digit characters have consecutive values, so that '1' == '0' + 1 ,

I have written the following code....It should convert a string like "88" to double value 88 and print it void convertType(char* value) { int i = 0; char ch; double ret = 0; while((ch = value[i] )!= '\0') { ret = ret*10 +(ch - '0'); ++i; } printf("%d",ret);//or %f..what is the control string for double? } //input string :88 But it always prints 0...But when i change type of ret to int ...it works fine...when the type is float or double,it prints zero...so why am i getting this ambiguous results? Use sscanf (header stdio.h or cstdio in C++): char str[] = "12345.56"; double d; sscanf(str, "%lf",

I'm parsing GPS status entries in fixed NMEA sentences, where fraction part of geographical minutes comes always after period. However, on systems where locale defines comma as decimal separator, atof function ignores period and whole fraction part. What is the best method to deal with this issue? Long/latitude string in stored in character array, if it matters. Example Code: m_longitude = atof((char *)pField); Where pField[] = "01000.3897"; Cross-platform project, compiled for Windows XP and CE. Comment to solution: Accepted answer is more elegant, but this answer (and comment) is also worth

Hopefully this is a very simple question. Following is the C pgm (test.c) I have. #include <stdio.h> //#include <stdlib.h> int main (int argc, char *argv[]) { int intValue = atoi("1"); double doubleValue = atof("2"); fprintf(stdout,"The intValue is %d and the doubleValue is %g\n", intValue, doubleValue); return 0; } Note that I am using atoi() and atof() from stdlib.h, but I do not include that header file. I compile the pgm (gcc test.c) and get no compiler error! I run the pgm (./a.out) and here is the output, which is wrong. The intValue is 1 and the doubleValue is 0 Now I include stdlib.h

#必须是u类型==================u==================== by gisoracle def dmstod(dms): #arcpy.AddMessage("======================gisoracle==========="+dms+"==============================") try: p = dms.find('°') if p<0: return str(dms) #arcpy.AddMessage("p="+str(p)) d=string.atof(dms[0:p].strip()) #arcpy.AddMessage("d="+str(d)) p1=dms.find('′') #arcpy.AddMessage("p1="+str(p1)) if p1<0: p1=dms.find("'") f=0 # if p1>0: f=string.atof(dms[p+1:p1].strip()) else: p1=p #arcpy.AddMessage("f="+str(f)) p2=dms.find('″') if p2<0: p2=dms.find('"') #arcpy.AddMessage("p2="+str(p2)) s=0 # if p2>0: s=string.atof(dms[p1+1