13.2.3 The If..then..else statement

The If .. then .. else.. prototype syntax is

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If then statements

--          -  -        -     -        --------------------------
  if statement if expression  then   statement  -    -        --|
                                          else  statement
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The expression between the if and then keywords must have a Boolean result type. If the expression evaluates to True then the statement following the then keyword is executed.

If the expression evaluates to False, then the statement following the else keyword is executed, if it is present.

Some points to note:

For example:

If exp1 Then  
  If exp2 then  
    Stat1  
else  
  stat2;

Despite its appearance, the statement is syntactically equivalent to

If exp1 Then  
   begin  
   If exp2 then  
      Stat1  
   else  
      stat2  
   end;

and not to

{ NOT EQUIVALENT }  
If exp1 Then  
   begin  
   If exp2 then  
      Stat1  
   end  
else  
   stat2;

If it is this latter construct which is needed, the begin and end keywords must be present. When in doubt, it is better to add them.

The following is a valid statement:

If Today in [Monday..Friday] then  
  WriteLn ('Must work harder')  
else  
  WriteLn ('Take a day off.');