Develop Reference

Strange FormatException when converting to octal

So I have an integer number 208 I don't expect many to understand why I am doing this, but the end result of what I am trying to do is get the base-10 representation of octal number 208 (two-zero-eight). I expect that the confusing thing (for people that will try and answer this question) is that while 208 is an integer, I am using it more like a string containing the characters two, zero, and eight. Please let me know if there are any more questions on this, as I think it will cause some confusion.
Anyway, to get the base-10 representation of "208" here is what I do:
Convert int 208 into string "208".
Take the string "208", and parse from octal to decimal.
Then, here is the corresponding source code:
public byte OctalToDecimal(int octalDigits)
{
byte decimalValue = 0;
string octalString = string.Empty;
// first, get a string representation of the integer number
octalString = octalDigits.ToString();
// now, get the decimal value of the octal string
decimalValue = Convert.ToByte(octalString, 8);
// set the decimal-value as the label
return decimalValue;
}
I get a format exception when octalDigits = 208. I get a message about there being additional characters in the octalString's value. Why would that be? All I do is convert from int to string it's very short/simple, and not like I append anything on there. What is going on?

You should know that the digits for octal numbers are in the range 0 to 7
Here, some helpful links
the octal representations of bytes range from 000 to 377?
http://www.asciitable.com/

Octal numbers can not contain digit 8, like base-10 representation can't contain "digit" 10 and binary can't contain digit 2.

How can I get the IndexOf() method to return the correct values?

I have been working with googlemaps and i am now looking to format coordinates.
I get the coordinates in the following format:
Address(coordinates)zoomlevel.
I use the indexof method to get the start of "(" +1 so that i get the first number of the coordinate and store this value in a variable that i call "start".
I then do them same thing but this time i get the index of ")" -2 to get the last number of the last coordinate and store this value in a variable that i call "end".
I get the following error:
"Index and length must refer to a location within the string.Parameter name: length"
I get the following string as an imparameter:
"Loddvägen 155, 840 80 Lillhärdal, Sverige (61.9593214318303,14.0585965625)5"
by my calculations i should get the value 36 in the start variable and the value 65 in the end variable
but for some reason i get the values 41 in start and 71 in end.
why?
public string RemoveParantheses(string coord)
{
int start = coord.IndexOf("(")+1;
int end = coord.IndexOf(")")-2;
string formated = coord.Substring(start,end);
return formated;
}
I then tried hardcoding the correct values
string Test = cord.Substring(36,65);
I then get the following error:
startindex cannot be larger than length of string. parameter name startindex
I understand what both of the errors mean but in this case they are incorrect since im not going beyond the strings length value.
Thanks!

The second parameter of Substring is a length (MSDN source). Since you are passing in 65 for the second parameter, your call is trying to get the characters between 36 and 101 (36+65). Your string does not have 101 characters in it, so that error is thrown. To get the data between the ( characters, use this:
public string RemoveParantheses(string coord)
{
int start = coord.IndexOf("(")+1;
int end = coord.IndexOf(")")-2;
string formated = coord.Substring(start, end - start);
return formated;
}
Edit: The reason it worked with only the coordinates, was because the length of the total string was shorter, and since the coordinates started at the first position, the end coordinate was the last position. For example...
//using "Loddvägen 155, 840 80 Lillhärdal, Sverige (61.9593214318303,14.0585965625)5"
int start = coord.IndexOf("(") + 1; // 36
int end = coord.IndexOf(")")-2; // 65
coord.Substring(start, end); //looks at characters 35 through 101
//using (61.9593214318303,14.0585965625)5
int start = coord.IndexOf("(") + 1; // 1
int end = coord.IndexOf(")")-2; // 30
coord.Substring(start, end); //looks at characters 1 through 31
The second instance was valid because 31 actually existed in your string. Once you added the address to the beginning of the string, your code would no longer work.

Extracting parts of a string is a good use for regular expressions:
var match = Regex.Match(locationString, #"\((?<lat>[\d\.]+),(?<long>[\d\.]+)\)");
string latitude = match.Groups["lat"].Value;
string longitude = match.Groups["long"].Value;

You probably forgot to count newlines and other whitespaces, a \r\n newline is 2 "invisible" characters. The other mistake is that you are calling Substring with (Start, End) while its (Start, Count) or (Start, End - Start)

by my calculations i should get the value 36 in the start variable and the value 65 in the end variable
Then your calculations are wrong. With the string above I also see (and LinqPad confirms) that the open paren is at position 42 and the close paren is at index 73.
The error you're getting when using Substring is becuase the parameters to Substring are a beginning position and the length, not the ending position, so you should be using:
string formated = coord.Substring(start,(end-start+1));

That overload of Substring() takes two parameters, start index and a length. You've provided the second value as the index of the occurance of ) when really you want to get the length of the string you wish to trim, in this case you could subtract the index of ) from the index of (. For example: -
string foo = "Loddvägen 155, 840 80 Lillhärdal, Sverige (61.9593214318303,14.0585965625)5";
int start = foo.IndexOf("(") + 1;
int end = foo.IndexOf(")");
Console.Write(foo.Substring(start, end - start));
Console.Read();
Alternatively, you could parse the string using a regular expression, for example: -
Match r = Regex.Match(foo, #"\(([^)]*)\)");
Console.Write(r.Groups[1].Value);
Which will probably perform a little better than the previous example

string input =
"Loddvägen 155, 840 80 Lillhärdal, Sverige (61.9593214318303,14.0585965625)5";
var groups = Regex.Match(input,
#"\(([\d\.]+),([\d\.]+)\)(\d{1,2})").Groups;
var lat = groups[1].Value;
var lon = groups[2].Value;
var zoom = groups[3].Value;

Problems parsing through string in C#

I am trying to parse through the first three characters of a string.
public List<string> sortModes(List<string> allModesNonSorted)
{
foreach (string s in allModesNonSorted)
{
char firstNumber = s[0];
char secondNumber = s[1];
char thirdNumber = s[2];
char.IsDigit(firstNumber);
char.IsDigit(secondNumber);
char.IsDigit(thirdNumber);
combinedNumbers = Convert.ToInt16(firstNumber) + Convert.ToInt16(secondNumber) + Convert.ToInt16(thirdNumber);
}
return allModesNonSorted;
}
It recognizes each character correctly, but adds on an extra value 53 or 55. Below when I add the numbers, the 53 and 55 are included. Why is it doing this??

53 is the Unicode value of '5', and 55 is the Unicode value of '7'. It's showing you both the numeric and character versions of the data.
You'll notice with secondNumber you see the binary value 0 and the character value '\0' as well.
If you want to interpret a string as an integer, you can use
int myInteger = int.Parse(myString);
Specifically if you know you always have the format
input = "999 Hz Bla bla"
you can do something like:
int firstSeparator = input.IndexOf(' ');
string frequency = input.Substring(firstSeparator);
int numericFrequency = int.Parse(frequency);
That will work no matter how many digits are in the frequency as long as the digits are followed by a space character.

53 is the ASCII value for the character '5'
57 is the ASCII value for the character '7'
this is just Visual Studio showing you extra details about the actual values.
You can proceed with your code.

Because you're treating them as Characters.
the character '5' is sequentially the 53rd character in ASCII.
the simplest solution is to just subtract the character '0' from all of them, that will give you the numeric value of a single character.

53 and 55 are the ASCII values of the '5' and '7' characters (the way the characters are stored in memory).
If you need to convert them to Integers, take a look at this SO post.

Conversion of a Char variable to an integer

why is the integer equivalent of '8' is 56 in C sharp? I want to convert it to an integer 8 and not any other number.

You'll need to subtract the offset from '0'.
int zero = (int)'0'; // 48
int eight = (int)'8'; // 56
int value = eight - zero; // 8

56 is the (EDIT) Unicode value for the character 8 use:
Int32.Parse(myChar.ToString());
EDIT:
OR this:
char myChar = '8';
Convert.ToInt32(myChar);

The right way of converting unicode characters in C#/.Net is to use corresponding Char methods IsDigit and GetNumericValue (http://msdn.microsoft.com/en-us/library/e7k33ktz.aspx).
If you are absolutely sure that there will be no non-ASCII numbers in your input than ChaosPandion's suggestion is fine too.

Guid to Base34 encoder/decoder

Does anyone have a nice code snippet for a Guid to Base34 encoder/decoder, I've googled around for it previously and never really found any good sources.

This Number base conversion class in C# could be fairly easily extended to do base34 (or others if you think people will confuse S and 5 or b and 6 or i and j or B and 8 or 9 and g or whatever)

Here's a simplified version... It basically takes a string, calculates the MD5 hash, extracts the first four bytes as an unsigned long (effective mapping the string to a 4-byte number), converts that to base36 and then swaps out the "oh" and "zero" chars for "X" and "Y". Then, it ensures the final string is only six chars, padding with "Z" chars if needed.
require 'digest/md5'
# create an easy-to-read 6-digit unique idno
idno = original # starting string
idno = Digest::MD5.digest(idno).unpack("N").first # digest as unsigned long
idno = idno.to_s(36).upcase.tr("0O","XY") # convert to base34 (no "oh" or "zero")
idno = idno[0,6].ljust(6,"Z") # final 6-digit unique idno (pad with "Z" chars)

The key methods here are ToByteArray and this particular constructor.
Encode:
string encodedGuid = Convert.ToBase64String(guid.ToByteArray());
Decode:
Guid guid = new Guid(Convert.FromBase64String(encodedGuid));