StrToInt64Def

function StrToInt64Def(S: string; def: Int64): Int64;

Example

procedure ScriptEvent(var Value: variant);
begin
  Value := StrToInt64Def('missing', 0);  // 0
end;

Usage

StrToInt64Def parses text as a signed 64-bit integer, returning a supplied value on failure.

Parameters

Name	Type	Description
S	string	Signed decimal or $/0x hexadecimal integer text for an Int64 destination.
def	Int64	Value returned when S is syntactically invalid, partially valid or out of range.

Returns

The parsed signed 64-bit value, or def after a conversion failure. A return equal to def does not indicate which path was taken.

Errors

Normal Val conversion failures return def. Unexpected allocation or runtime failures are not part of the fallback contract and can still propagate.

Usage notes

Choose def outside the valid business domain where possible, even though every Int64 remains syntactically convertible. If the application must distinguish invalid text from that sentinel, validate separately rather than comparing only the return.

Additional Technical Info

StrToInt64Def parses signed decimal or Delphi-style hexadecimal text into Int64, returning def when conversion fails. It shares StrToInt64's parser and range but suppresses its ordinary conversion exception.

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

Implementation

With PascalScript Int64 support enabled, runtime dispatch case 41 passes the script string and stack Int64 fallback to Delphi System.SysUtils.StrToInt64Def. The terminal calls Val with an Int64 destination and substitutes def whenever the returned error position is non-zero.

Edge cases and quirks

• The fallback covers both malformed input and signed 64-bit overflow/underflow.
• Decimal points, grouping characters and partially valid tokens fail as a whole.
• Delphi's hexadecimal form is bit-pattern oriented for the signed destination. High-bit-set 16-digit values can produce negative results rather than the fallback; more than 16 hexadecimal digits fail.
• def can equal a legitimately parsed value. This API deliberately provides no success flag.
• Free Pascal exposes the same high-level fallback shape, but its accepted prefixes and whitespace rules are dialect-specific.
• The function is present in the current Velox build because PascalScript 64-bit integer support is enabled.

Side effects

None.

Performance and concurrency

Linear in input length with no locale lookup or shared state.

Related entries

• StrToInt64 raises on the same conversion failures.
• StrToIntDef provides a 32-bit fallback conversion.
• StrToUInt64Def covers the unsigned 64-bit range.

External references

• Free Pascal StrToInt64Def - compatible fallback reference with dialect-specific parser details.
• Embarcadero System.SysUtils.StrToInt64Def - the exact Delphi terminal called by PascalScript.

Created 2026-07-15