如何做数学运算用ASCII？ [英] How to do math operations in Ascii?

问题描述

我试图解析纬度，从GPS NMEA数据包经度值。我收到的数据包作为一个字符数组。我分析的纬度数组，现在我需要做的就可以了乘法运算。但它是一个字符数组。例如，下面是一个例子数组：

I'm trying to parse the latitude,longitude values from a GPS NMEA Packet. I receive the packet as a char array. I parsed the latitude array and now i need to do a multiplication operation on it. But it is a char array. For example, here is an example array:

char *latitude;

latitude[0] = '4';
latitude[1] = '0';
latitude[2] = '5';

我想通过2.必须分别输出8,0,10乘以这个值。所以我需要得到4,2,6值作为整数。但是，如果我作为整数使用该数组的内容，它自然输出52,48,53。我不想让这相当于这些ascii字符的整数值，我想要得到的实际值，因为我看到的。

I want to multiply this values by 2. It must output 8,0,10 respectively. So i need to get the 4,2,6 values as integer. But if i use this arrays content as integer, it naturally outputs 52,48,53. I dont want to get the integer value which corresponds these ascii characters, i want to get the actual value as i see.

推荐答案

首先，你要保证人数为单数位或已搬运就位。请大家注意，字符 s时，可以作为没有明确的转换整数，由于整型提升。例如，如果

First of all, you have to ensure the numbers are either single digit or you have handling in place. Please do note that chars can be used as integers without explicit conversion, due to integer promotion. For instance, if

latitude[0] = '1';
latitude[1] = '3';
latitude[2] = '9';

您必须在一起通过这些分开，然后猫。您可以通过减去获得字符的 INT 值0，因为所有的个位数 INT 值连续给对方。对于这一点，写这样的功能：

You have to pass these seperately and then cat them together. You can get the int value of a char by subtracting '0' since all single digit int values in ascii are sequential to each other. For this, write a function like this:

int asciiToInt (char ascii) {
if ( ascii < '0' || ascii > '9' ) {
return -1; //error
}
else
{
return (int)(ascii - '0'); // This works because '0' has the int value 48 in Ascii and '1' 49 and so on.
}
}

然后调用它像这样

Then call it like this

int a = asciiToInt(latitude[0])*2;

或者，如果你想有一个3位数

Or, if you want to have a 3 digit number

int a;
a = asciiToInt(latitude[0]);
a += asciiToInt(latitude[1])*10;
a += asciiToInt(latitude[2])*100;
a = a*2;

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