Revision as of 21:24, 12 August 2018

The $base identifier converts numbers between different number bases, or zero-pads numbers to the desired length.

Synopsis

$base(<N>,<InBase>,<OutBase>[,Zero-pad][,Precision])

Parameters

NThe Number being converted.
InBaseThe Number Base in which N is being expressed.
OutBaseThe Number Base to which N is being converted. Can be same as InBase.
ZeroPadThe output's minimum number of non-fraction digits by adding 0's if needed. Accepts up to 100.
PrecisionThe output's maximum number of fraction digits, limited by mIRC's base-10 precision of 6.

• Note: InBase & Outbase can be any integer from 2-36, with Base 17-36 extending hexadecimal to use as many letters as needed from the G-Z range. Letters A-Z used by number bases 11 through 36 are case-insensitive.
• Note: Prefix 0x or 0X is stripped from N for all bases 2-35 but not base36. To prevent this, such as in base 34-35 where X is a valid character, prefix the input string with 00.
• Note: Base 32 is NOT the same as the base32 encoding method used by $encode(). $base assigns the values 0-31 to characters 0-9 and A-V, while the Base32 encoding method assigns values 0-31 to A-Z and 2-7 then stores them differently.

Properties

None

Example

Without changing number base, can use $base to left-zero-pad or truncate (not round) fractions to fewer digits:
//echo -a $base(123.456,10,10,6,2)
returns: 000123.45
 
//var %n $color(8) | echo -a %n $base(%n,10,16,6)
converts the {{mIRC|$color}} number for yellow from decimal to hexadecimal, zero padded to 6 digits.
Output is 00FFFF not FFFF00 because mIRC stores colors as GBR not RGB.
 
//var %n $pi  | echo -a %n $base(%n,10,16,0,12) $base($calc(%n * 16^6),10,16,6,12) 
; returns: 3.14159265358979323846 3.243F7 3243F6A.8885A
; precision of output is input rounded to 6 fraction digits
//echo -a $base(1.0000005,10,10) returns 1.000001  
 
//var %n $crc(abc,0) | echo -a %n $base(%n,16,36,7)
; Converts 8-digit hexadecimal
; Base 36 extends the hexadecimal alphabet so the characters G-Z have decimal values 16-35
 
//var %n $str(F,9) | echo -a converts 9-digit hex number %n to 7-digit base-36 $base(%n,16,36,7)
; returns: converts 9-digit hex number FFFFFFFFF to 7-digit base-36 VKHSVLR

You should not attempt to input numbers greater than decimal 2^53. For N=1+2^n, this shows that even though $base fails to convert back to the original number starting with N=55, $calc failed to create an odd-numbered number at N=53.
 
//var %i 1 | while (%i isnum 1-64) { var %n $calc(1+2^%i ) | echo -a %i %n $base(%n,10,16) $base($base(%n,10,16),16,10) | inc %i }
 
$base allows invalid letters to be used in the input, assigning them values as they have in Base 36.
 
//echo -a $base(mIRC,10,10) is same as $calc(22*1000 + 18*100 + 27*10+ 12*1)
 
The exception to the above is recognizing the 0x prefix for hexadecimal notation. Converting from base-16 to base1- results in 255 for both 0xFF and FF. The 0x or 0X prefix is ignored in every base except 36:
 
//var %i 2 , %a , %value F | while (%i isnum 2-36) { var %a %a $+(base,%i,=,$base(0x $+ %value,%i,10),vs,$base(%value,%i,10)) | inc %i } | echo -a %a
 
If using base 34 or 35 where X is a valid character, you must prepend the from-value with 00 to prevent 0x from being stripped:
//var %value 0xF | echo -a $base(%value,35,10) vs $base(00 $+ %value,35,10)
returns: 15 vs 1170
 
To store the 128 hexadecimal digits of the sha512 hash digest in fewer digits, you can't use $base to accurately translate more than 13 digits at a time.
//var %digits 13 , %from_base 16 , %to_base 36 | echo -a $calc( %digits * $log(%from_base) / $log(%to_base) )
//var %digits  9 , %from_base 16 , %to_base 36 | echo -a $calc( %digits * $log(%from_base) / $log(%to_base) ) 
These show that base36 requires 10.05 digits to store 13 hex digits, or 6.96 digits to store 9 hex digits. Rounding up, this means both methods shrink the strings by the same 4 digits. (13->11 vs 9->7) It's more efficient to translate the string 9 digits at a time into 14 groups of 9, then translate the remaining 2 digits separately, for a total length of 14*7+2=100:
 
alias short_hash {
  var %long $sha512($1) , %short , %hash %long | while ($len(%hash) >= 9) {
    var %temp $right(%hash,9) , %hash $left(%hash,-9) , %short $base(%temp,16,36,7) $+ %short
    echo -a %hash %temp -> $left(%short,7)
  }
  var %short $base(%hash,16,36,2) $+ %short
  echo -a shortened $len(%long) %long to $len(%short) %short
  return %short
}
 
/short_hash abc
returns:
shortened 128 d8022f2060ad6efd297ab73dcc5355c9b214054b0d1776a136a669d26a7d3b14f73aa0d0ebff19ee333368f0164b6419a96da49e3e481753e7e96b716bdccb6f to 100 6009P25MYQI73NNEMLHK0MTBF48SUD996MZJE2E6ZVTED4R1VM7E9HEQ5NVGI65GZ6Q7J6FFCCDZ2ZE9413JTJACHSWXJ2SYIR1R

Compatibility

Added: mIRC v5.7
Added on: 02 Feb 2000
Note: Unless otherwise stated, this was the date of original functionality.
Further enhancements may have been made in later versions.

See also

• $calc
• $encode