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StrToBool

function StrToBool(const S: string): Boolean;

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := StrToBool('true');  // True
end;

Usage​

StrToBool converts recognised numeric or Boolean text to a Boolean and raises for unrecognised input.

Parameters

NameTypeDescription
SstringNumeric or named Boolean text. Named values are matched without regard to case. The default names are True and False.

Returns

False for numeric zero or a recognised false name; True for a non-zero number or a recognised true name.

Errors

Text that is neither a valid number nor a configured Boolean name raises EConvertError, which propagates as a script runtime exception. Use StrToBoolDef for a fallback or TryStrToBool when failure must remain explicit without an exception.

Usage notes

Use named True/False text for human-readable configuration and numeric 0/1 only when that contract is deliberate. Do not treat every non-empty string as true.

Additional Technical Info​

StrToBool converts numeric text or a recognised Boolean name to Boolean. It tries floating-point conversion first: numeric zero becomes False, while any non-zero numeric value becomes True. If the text is not numeric, it performs a case-insensitive comparison with Delphi's process-wide true and false string arrays.

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

Implementation

Velox registers a small scripting adapter that calls Delphi System.SysUtils.StrToBool. The Delphi terminal calls TryStrToBool; that routine first calls the global-format overload of TryStrToFloat, then lazily initialises and searches TrueBoolStrs and FalseBoolStrs only when numeric parsing fails. An unrecognised value causes StrToBool to raise EConvertError.

Edge cases and quirks

  • Numeric parsing precedes named-value matching. Values such as -1, 2.5 or 1E3 are therefore valid and return True; this is broader than accepting only True and False.
  • The numeric path uses Delphi's process-global FormatSettings, not the fresh Windows system-locale settings used by Velox StrToFloat. A decimal string can consequently be interpreted differently by the two public functions if those settings differ.
  • The installed Delphi parser recognises NAN, INF, +INF and -INF as floating special values. They enter the numeric path; the current non-zero comparison produces True. Avoid using special floating values as Boolean input.
  • Named values are case-insensitive but are not trimmed by the Boolean-name comparison. Numeric parsing accepts its own leading/trailing-space grammar; a spaced named value such as " true " is not a match.
  • TrueBoolStrs and FalseBoolStrs are mutable process-wide arrays. Empty arrays are populated lazily with True and False; host customisation can add other accepted names.

Side effects

The first non-numeric Boolean conversion can initialise the two process-wide Boolean string arrays. The function does not change Velox data or module state.

Performance and concurrency

Work is linear in the input and configured-name lengths. Numeric parsing reads shared global format settings, and named parsing can lazily mutate shared arrays, so this Delphi overload is not a fully isolated thread-local conversion.

Related entries

  • StrToBoolDef returns a caller-supplied fallback for unrecognised text.
  • TryStrToBool reports conversion success separately from the parsed value.
  • StrToFloat exposes Velox's system-locale floating parser directly.

External references

Created 2026-07-15