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BreakStringLast

Procedure BreakStringLast(S: string; const aSep: string; var Head, Tail: string)

Example​

procedure ScriptEvent(var Value: variant);
var
  Head, Tail: string;
begin
  BreakStringLast('archive.2026.csv', '.', Head, Tail);
  Value := Head + ' / ' + Tail; // archive.2026 / csv
end;

Usage​

BreakStringLast splits at the last matching delimiter character; multi-character separator input triggers a current length-handling defect.

Parameters

NameModeDescription
SinputSource text; not modified.
aSepinputDelimiter characters passed to Velox LastDelimiter. For reliable results, supply exactly one character.
Headoutput through varText before the located character, or all of S if none is located.
Tailoutput through varText after the removed region, or empty if no delimiter is located.

Additional Technical Info​

BreakStringLast divides text at the last occurrence of a delimiter character. With the supported, safe usage of a one-character aSep, it returns the text before that character in Head and the text after it in Tail.

The example is fictional and source-reviewed only.

Current implementation defect

The name and declaration suggest that aSep is one substring, but the implementation combines incompatible rules:

  1. LastDelimiter(aSep, S) treats every character in aSep as a separate valid delimiter and locates the last occurrence of any one of them.
  2. The helper then advances by Length(aSep) as though the entire string had matched at that location.

For example, passing '::' does not search for the last two-character token. It finds the last ':' character and skips two characters from there, which can remove the first character of the intended tail. Passing '/\\' searches for either slash but then skips two code units. This mismatch can silently corrupt a split result.

Restrict aSep to one character. To split around the first exact multi-character token, use BreakString. To find a last multi-character substring, use an explicit search strategy rather than this helper.

Other edge cases

  • A delimiter at the first position produces an empty Head.
  • A delimiter at the last position produces an empty Tail.
  • No match, including an empty delimiter set, produces Head = S and Tail = ''.
  • Matching is case-sensitive and delimiter-character based; it does not honour escaping or quoting.
  • Delphi's terminal ignores the NUL character as a delimiter, so #0 is not a reliable separator here.

External references

Created 2026-07-15