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TvxChars

TvxChars = set of Char

Example​

function IsAsciiDigits(const Value: String): Boolean;
var
  Digits: TvxChars;
begin
  Digits := ['0'..'9'];
  Result := StringContainsOnly(Value, Digits);
end;

Usage​

TvxChars defines an 8-bit character membership set for Velox removal and validation string helpers.

Character-domain boundary​

The current script Char and a set's ordinal range are eight-bit, while script String is Unicode. TvxChars can therefore describe only character values with ordinals 0..255. It is suitable for ASCII-oriented protocol characters and carefully defined Latin-1-range values; it cannot represent general Unicode characters, supplementary characters or grapheme clusters.

Do not assume a visually similar Unicode character matches an ASCII member. Normalize and validate with a Unicode-aware function when the business rule is about human text rather than protocol code units.

Current helper behavior​

  • RemoveChars2 scans from the first character and copies every character not present in the set.
  • StringContainsOnly returns true only when the source is nonempty and every scanned character is in the set. It deliberately returns false for '', even if the set is nonempty.
  • Both implementations convert the source to a Velox PChar and stop at the first #0. Characters after an embedded NUL are not examined; RemoveChars2 also omits that NUL and the suffix.
  • Both build/scan in memory and perform no trimming, normalization, case folding or locale-aware comparison.

If embedded NUL or non-ASCII input is possible, reject it before using these helpers or use a function with an explicit Unicode/string-length contract.

Additional Technical Info​

TvxChars is registered by the Velox common-string importer for RemoveChars2 and StringContainsOnly. It is a fixed membership set over the public PascalScript Char domain.

Related Code Library entries

  • Char - the current 8-bit script character boundary.
  • Sets - constructors, ranges and membership operations.

External references

Created 2026-07-15