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begin..end

Use begin and end to group zero or more statements into one compound statement. A compound statement is useful anywhere the grammar accepts one statement, including an event body, an if branch or a loop body.

Syntax​

begin
  Statement1;
  Statement2;
end;

The semicolon separates statements; it is not part of the begin or end keywords. The final statement before end may omit its semicolon, although retaining it makes later edits safer. A semicolon after end is needed when another statement follows at the same level.

How it works​

Velox compiles scripts with its modified PascalScript compiler. TPSPascalCompiler.ProcessSub enters a nested block when it reads begin, compiles each contained statement in source order, and leaves the block at the matching end. The block itself does not create an independently callable routine or transaction.

Velox enables icAllowNoBegin and icAllowNoEnd for the outer script. Consequently, a complete script supplied to an event can omit an otherwise conventional outer program begin..end wrapper. This option does not remove the need for begin..end when several statements must occupy a grammar position that accepts only one statement.

Blocks may be nested. Local variable declarations still belong at the start of their procedure or function; placing a var declaration inside an executable block is not supported by this grammar.

Example​

procedure ScriptEvent(var Value: Variant);
begin
  Value := 'started';
  begin
    Value := Value + ' and completed';
  end;
end;

The nested block is legal but unnecessary here; it demonstrates that its statements execute at the point where the block appears.

Common mistakes​

  • Omitting begin..end after an if or loop when more than one statement is intended. Only the immediately following statement belongs to that branch or loop.
  • Adding a semicolon before the else of an if..else. That terminates the then statement and prevents the parser from associating the else correctly.
  • Missing the matching end. Compilation fails, commonly with an END expected or related structural error at the point where the parser can no longer complete the block.
  • Assuming a block isolates failures or rolls back changes. It provides syntax grouping only; called functions, object setters and dataset operations keep their normal side effects.

Edge cases and quirks​

  • An empty block (begin end) is accepted and performs no operation.
  • A stand-alone semicolon is an empty statement. Multiple semicolons therefore compile, but usually indicate accidental or unclear code.
  • The main script can omit its outer begin or final end because of Velox compiler options. Examples retain a conventional procedure block because event signatures still need a clear executable body.
  • begin..end does not introduce block-local variable scope in the way braces do in some other languages.

Performance and concurrency​

The block adds no material runtime work beyond its contained statements. It provides no locking or concurrency boundary; any shared objects exposed by Velox retain their own lifetime and thread-safety rules.

  • if and if..else — use a compound block when a branch must execute several statements.
  • for loop, while loop and repeat loop — blocks define a multi-statement loop body.
  • try..except and try..finally — these statements use block-like regions but also install runtime exception handling.

External references​