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### B.1.9 Strings

String manipulation and query functions.

concat( s1, s2 )
  Concatenates two strings. In most cases the same effect can be achieved by writing `s1+s2`, but blank values can sometimes appear as the string "`null`" if you do it like that.
concat( s1, s2, s3 )
  Concatenates three strings. In most cases the same effect can be achieved by writing `s1+s2+s3`, but blank values can sometimes appear as the string "`null`" if you do it like that.
concat( s1, s2, s3, s4 )
  Concatenates four strings. In most cases the same effect can be achieved by writing `s1+s2+s3+s4`, but blank values can sometimes appear as the string "`null`" if you do it like that.
equals( s1, s2 )
  Determines whether two strings are equal. Note you should use this function instead of `s1==s2`, which can (for technical reasons) return false even if the strings are the same.
equalsIgnoreCase( s1, s2 )
  Determines whether two strings are equal apart from possible upper/lower case distinctions.
startsWith( whole, start )
  Determines whether a string starts with a certain substring.
endsWith( whole, end )
  Determines whether a string ends with a certain substring.
contains( whole, sub )
  Determines whether a string contains a given substring.
length( str )
  Returns the length of a string in characters.
matches( str, regex )
  Tests whether a string matches a given regular expression.
matchGroup( str, regex )
  Returns the first grouped expression matched in a string defined by a regular expression. A grouped expression is one enclosed in parentheses.
replaceFirst( str, regex, replacement )
  Replaces the first occurrence of a regular expression in a string with a different substring value.
replaceAll( str, regex, replacement )
  Replaces all occurrences of a regular expression in a string with a different substring value.
substring( str, startIndex )
  Returns the last part of a given string. The substring begins with the character at the specified index and extends to the end of this string.
substring( str, startIndex, endIndex )
  Returns a substring of a given string. The substring begins with the character at `startIndex` and continues to the character at index `endIndex-1` Thus the length of the substring is `endIndex-startIndex`.
toUpperCase( str )
  Returns an uppercased version of a string.
toLowerCase( str )
  Returns an uppercased version of a string.
trim( str )
  Trims whitespace from both ends of a string.
padWithZeros( value, ndigit )
  Takes an integer argument and returns a string representing the same numeric value but padded with leading zeros to a specified length.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk