IsCurrencyNumber

Function IsCurrencyNumber( const S : string) : Boolean

Example

procedure ScriptEvent(var Value: variant);
begin
  Value := IsCurrencyNumber('$1,234.50');
end;

Usage

IsCurrencyNumber checks that non-empty text contains only digits and the characters period, comma, dollar sign, minus or plus.

Parameters

Name	Type	Description
S	string, const	Text whose characters are inspected. No trimming or normalisation is performed.

Returns

False for an empty string or when any inspected character is outside the whitelist. Otherwise True.

Behaviour

The check is deliberately locale-independent. It accepts the literal period, comma and dollar sign regardless of the machine's decimal separator, thousand separator or currency symbol. ASCII digits alone also pass.

Errors

There is no normal exception path for a valid Velox string. Conversion or range errors can still occur later if the caller treats a True result as proof that the text parses.

Usage notes

Use this as an early filter only when this exact whitelist is required. A production currency rule should normally also define the currency, decimal/group separators, permitted sign notation, scale, rounding and range, then parse using those explicit format settings.

Additional Technical Info

IsCurrencyNumber checks whether a nonempty string contains only ASCII digits and the six punctuation characters ., ,, $, - and +. It is a character-whitelist helper, not a currency parser or a complete numeric validator.

The example returns True. It is source-reviewed and is not executed by the documentation workflow.

Implementation

The Velox function converts the Delphi string to PChar, advances until the first null character, and rejects a character unless it belongs to:

0..9  .  ,  $  -  +

It does not call a Delphi currency conversion routine, inspect format settings or count/position punctuation.

Edge cases and quirks

• Symbols can appear in any order, any position and any number of times. Values such as $$, +--, 1,2.3, ., and $- all pass the character whitelist.
• No digit is required. Punctuation-only text can return True.
• Leading/trailing whitespace, parentheses, other currency symbols and non-ASCII digits return False.
• The function does not enforce one decimal separator, valid grouping, sign position, decimal places, numeric range or currency code.
• An embedded #0 terminates the pointer loop. Any characters after it are ignored; a nonempty string beginning with #0 can return True without inspecting later content.
• The name can overstate the guarantee. True means only "all inspected characters are in this whitelist".

Side effects

None.

Performance and concurrency

Time is linear in the inspected prefix up to the first null character. The function allocates no transformed string and uses no shared mutable state.

Related entries

• IsNumber applies tighter sign and decimal-point placement but still does not parse.
• IsInteger accepts ASCII digits only.
• Comparison distinguishes lexical checks from numeric comparison.

Created 2026-07-15