Else

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Else at Language Reference

Else is keyword which introduces the action to do if the condition is false.

If then else

  if (condition)
  then true_statement
  else false_statement;

The value of condition is evaluated, if it resolves to true, the true_statement is executed, otherwise the false_statement is executed. The value of condition must resolve to a boolean value or an error occurs.

More statements in "if then else" statement

If you need two or more statements for true_statement or false_statement, then the group of statements must be placed within a begin ... end Block.

  if boolean_condition then
    begin
      statement_one;
      statement_two;
    end 
  else
    begin
      statement_three;
      statement_four;
    end;

Notice that before the else keyword, no semicolon (;) is allowed. In the above example the first "end" statement is not followed by a semicolon but the last one is.

The following code wil not compile:

    if a then
      if b then
        begin
           (..)
        end;
      else   // Fatal: Syntax error, ";" expected but "ELSE" found
        begin
           (..)
        end;

Having nested if..then..else statement can easlily lead to ambiguity: which else belongs to which if? In this case, the "else" applies to "not if b"

  if a then
      if b then
        begin
           DoB;
        end
      else
        begin
           DoNotB;
        end;

In this case, the "else" applies to "not if a". If this causes ambiguity, it can be resolved by coding an "empty" else statement:

  if a then
      if b then
        begin
          DoB
        end
      else
  else
      begin
        DoNotA
      end;

Keywords: begin — do — else — end — for — if — repeat — then — until — while