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Statements

Statements perform work or control which script code executes. Velox uses the PascalScript grammar, with generated child topics for compound blocks, conditions, case selection, for, while and repeat loops, and try..except/try..finally handling.

Basic forms​

procedure ScriptEvent(var Value: Variant);
var
  I: Integer;
begin
  if VarIsNull(Value) then
    Value := ''
  else
  begin
    for I := 1 to 3 do
      Value := VarToStr(Value) + '.';
  end;
end;

The source-reviewed example shows a simple statement after then and a compound begin..end statement after else.

Blocks and semicolons​

begin and end group several statements wherever the grammar expects one statement. A semicolon separates statements; it is not conceptually part of if, while or another construct. In particular, do not put a semicolon between an if branch and its else.

The event procedure's final end; closes the procedure. A full Delphi program normally ends in end., but Velox compiles event procedures and enables options that allow source without a traditional program main block.

Conditions and loops​

Conditions must produce Boolean-compatible values. Use explicit Variant tests before a Boolean conversion. A for loop evaluates a bounded ordinal range and changes its loop variable; a while loop tests before each pass; a repeat loop executes at least once and tests after the body.

Every loop in an integration must have a deterministic termination condition. Dataset loops normally advance with Next; omitting that call can hang the action. Long loops block the action thread and delay cancellation unless the called operations check it.

Exceptions and cleanup​

Use try..except when the script can safely handle a known failure and provide an appropriate result or log. Use try..finally to release a caller-owned object or restore state regardless of success. Do not free context-owned Velox objects in a finally block.

The surrounding Velox event boundary also catches exceptions, logs them and can change processing status. A local except that swallows an error prevents that boundary from seeing it; log or return a meaningful result when recovery is genuinely safe.

Common mistakes​

  • A stray semicolon before else, producing a syntax error or changing control flow.
  • Using = for assignment instead of :=.
  • Writing a dataset while not EOF loop without Next.
  • Using repeat when the body must not run for an initially false condition.
  • Catching every exception and continuing with partially changed data.
  • Creating an object and omitting try..finally when the entry says the caller owns it.

Edge cases and quirks​

  • This landing page documents the generated supported family; a statement accepted by modern Delphi is not automatically accepted by the current PascalScript compiler.
  • Boolean short-circuiting is enabled by Velox, which affects function calls inside and/or conditions.
  • Exit leaves the current procedure immediately and preserves any changes already made through var parameters.
  • Compiler errors can point into an included module; use the reported module and line rather than only the main editor line.
  • Operators — expressions used by assignments and conditions.
  • Comments — documenting non-obvious control flow.
  • Compilation errors — missing delimiters and structural diagnostics.

External references​