Hexadecimal To Decimal

Question

Read input of up to 8 characters presented as hexadecimal number and print this number as decimal number. In case that input can not be presented as hexadecimal input it has to print 0

Rules:
It is not allowed to use any function that takes or returns strings/characters, beside function that reads string/char from input and return strings/char as-is, function that takes integer and prints that integer to output as decimal number and function (if needed) that takes character and return its ASCII/UNICODE represented integer.

Shortest code wins

Example input
C0cAc01a

output
3234512922

Answer 1

Ruby, 74 characters

n=0;p gets.gsub(/./).all?{|x|n=n*16+(x>?9?9:0)+x.ord%16;/[\da-f]/i=~x}?n:0

Input must be given on STDIN. With command line option -ln (counted as 4) it can be shortened to 69 characters.

n=0;p chars.all?{|x|n=n*16+(x>?9?9:0)+x.ord%16;/[\da-f]/i=~x}?n:0

Answer 2

Haskell, 114 106

x#y=16*x+mod y 16
main=getLine>>=print.maybe 0(foldl(#)0).mapM(`lookup`zip"ABCDEF0123456789abcdef"[-6..])

Handles input of arbitrary size.

Answer 3

c -- 181

Input passed on the commandline (one argument only). Relies on K&R function typing defaults. ASCII specific, but has no reliance on the language or library to know how to parse numbers. Lots of characters given up to specifying a large integer type for this purpose.

#include <stdio.h>
main(int c,char**v){unsigned long b=0;char*d=v[1]-1,e;while(e=*++d){
e-=(e>96)?87:(e>64)?55:(e>57)?33:(e>47)?48:0;if(e>15){b=0;break;}
b=b*16+e;}printf("%lu\n",b);}

Ungolfed:

#include <stdio.h>
main(int c,char**v){
  unsigned long b=0;
  char*d=v[1]-1,e;
  while(e=*++d){
    if(e>'`')e-=87; // reduce lowercase letters to 10--
    if(e>'@')e-=55; // reduce uppercase letters to 10--
    if(e>'9')e-=33; // reduce punctioation immediately above the
                      // digits so it does not iterfere
    if(e>'/')e-='0';// reduce digits to 0-9
    if(e>15){b=0;break;} // terminate immediately on bad input
    b=b*16+e;
  }
printf("%lu\n",b);}

Validation:

$ gcc -o dehex dehex_golfed.c 
$ ./dehex C0cAc01a
3234512922
$ ./dehex 1       
1
$ ./dehex 1f
31
$ ./dehex g 
0
$ ./dehex 1g
1
$ ./dehex 1:2
0

Answer 4

JavaScript, 127 119 characters (thanks trinithis!)

Code-Golfed:

function f(n){for(o=i=0,c=1;l=n[i++];)o*=16,l=l.charCodeAt(0),o+=l-(l>96?87:l>64?55:48);return /[\W_g-z]/i.test(n)?0:o}

Formatted:

function hexToDec(hexChars) {
    //Iterate through hex chars
    for (dec=i=0,count = 1; hexChar = hexChars[i++];) {
        dec *= 16;
        hexCharCode = hexChar.charCodeAt(0);

        //Get the hex number and add it
        hex = hexCharCode;
        if(hexCharCode > 96){
            hex -= 87;//For lower case letters
        } else if (hexCharCode > 64){
            hex -= 55;//For upper case letters
        } else {
            hex -= 48;//For numbers
        }
        dec += hex;
    }

    //Return 0 if invalid, decimal value otherwise
    if(/[\W_g-z]/i.test(hexChars)){
        return 0;
    }
    return dec;
}

Answer 5

Ruby 1.9 (84)

gets.chomp!;n=0;p~/[^0-9A-Fa-f]/?0:($_.chars{|c|o=c.ord-48;n=16*n+(o>9?o%32-7:o)};n)

If we're allowed to use command line options, this is shortened to 72 characters + 4 for -ln:

n=0;p~/[^0-9A-Fa-f]/?0:($_.chars{|c|o=c.ord-48;n=16*n+(o>9?o%32-7:o)};n)

Answer 6

Python, 106 characters

n=0
e=9e9
for c in raw_input():n=n*16+ord(c)-[e,48,e,55,e,87,e][sum(c>x for x in'/9@F`f')]
print[n,0][n<0]

Answer 7

Scheme, 24 chars

(string->number(read)16)

I hope this is not considered cheating. If it is:

(string->number(string-append "#x"(read)))

String to number conversion is mandatory.

In Scheme, if your program is not simple, something is wrong and you should start over until it is made simple. Scheme's power relies on removing restrictions instead of adding features so that the language can be easily extended. Scheme is, with Lisp-derived languages, a programmable programming language.

Answer 8

D 194 chars

void main(string[] a){ulong r;foreach(c;a[1]){switch(c){case '0'..'9':r+=c-'0';break;case 'a'..'f':r+=c-'a'+10;break;case 'A'..'F':r+=c-'A'+10;break;default: write(0); return;}r*=16;}write(r);}

I could get some profit by replacing the char literals with the numerals and get thus get rid of the +10 for the a-f but this doesn't depend on char encoding though D defines ascii support IIRC

Answer 9

Mathematica, 64

By the rules:

FromDigits[#-If[#<58,48,If[#<97,55,87]]&/@ToCharacterCode@#,16]&

Answer 10

JavaScript, 48 chars

function h(n){return 0/0==+("0x"+n)?0:+("0x"+n)}

Formatted + Uncompressed

function h(n){
    if(+("0x"+n)==NaN) {
        return 0;
    }
    else {
        return +("0x"+n);
    }
}

The plus operator set before a string converts it into a decimal number. So I just had to prepend a "0x" and return 0 if it isn't a valid number to conform the rules.

Answer 11

Groovy, 74

i={it.inject(0){a,v->a*16L+('0123456789abcdef'.indexOf(v.toLowerCase()))}}

test case:

assert 3234512922 == i('C0cAc01a')

Not sure I understood the rules, though.

Answer 12

Perl, 39 characters

print<>=~m/^[[:xdigit:]]{1,8}$/?hex$&:0

I kind of feel weird doing it this way in Perl but I believe it follows the rules, since the hex() function is a language construct and not a library function. If not...

Perl, 64 characters

print<>!~m/^[[:xdigit:]]{1,8}$/?0:unpack 'L',reverse pack'H8',$&

I hope is fine.

Answer 13

C# - 192 189

oldschool, uses Console arguments for input, Console.WriteLine() for output. could possibly save a few chars, but can't get rid of most lengthy keywords. Makes evil use of foreach, ternary operator madness, bitwise complement ~ and signedness. Reads any length input and aborts on bad characters ([^0-9a-fA-F]).

namespace _{class _{static void Main(string[]a){long b=0;foreach(int c in a.Length>0?a[0]:"")b=b<<4|(c-'0'<10?c-'0':c-'A'<6?c-'A'+10:c-'a'<6?c-'a'+10:~0L);System.Console.Write(b<0?0:b);}}}

A little deobfuscated (old ver):

using System;
namespace CodeGolf
{
    class Program
    {
        static void Main()
        {
            long ret = 0;
            int nextChar;

            while ((nextChar = Console.Read()) != '\r')
            {
                ret <<= 4;
                ret |= nextChar - '0' < 10 ? 
                        nextChar - '0' : 
                        nextChar - 'A' < 6 ? 
                            nextChar - 'A' + 10 : 
                            nextChar - 'a' < 6 ? 
                                nextChar - 'a' + 10 : 
                                ~0L;
            }

            Console.WriteLine(ret < 0 ? 0 : ret);
        }
    }
}

Would love to see a C# implementation in hardcore MSIL ;)

Answer 14

Python, 98 chars

print sum(16**n*i for i,n in zip(((ord(c)|32)-[48,87][c>'9']for c in raw_input()[::-1]),range(9)))

A one-liner with the nifty bonus that you can use characters > 'f' for shorthand notation, e.g 'g' counts for 16, 'h' for 17 etc :D

Answer 15

Mathematica 93 92 chars

Fold[16 #1 + #2 &, 0,ToExpression[Characters@n /. Thread@Rule["a"~CharacterRange~"f", 10~Range~15]]]

Not as streamlined as Mr.Wizard's answer, but I'll include it for variety. It makes use of no native base conversion routines. There is a shortcoming in my answer: I assumed that characters a to f would be given in lowercase.

Answer 16

Perl - 77 chars

@h{0..9,'a'..'f'}=0..15;$n+=$h{lc$_}*16**($a++-1)for reverse split//,<>;say$n