missing semicolon

[cousinp]

Code: Pascal  [Select][+][-]

1.  

if (i >= 1) and (i<= 7) then
  begin
    if sw= 'Full' then
    writeln('The day in words is: ' + tmpStr)
    else
     writeln('The day in words is: ' + leftStr(tmpStr,3));
  end;
end;

The above code is from the book, part of a program
On the first 'writeln' there is no semicolon.
But the second 'writeln' has one, why not the first also.
I have tried no semicolons and the code does not produce an error and the program works.
I have also tried a semicolon on both statements and the code does not compile.
All previous 'writeln' statements in the book ended with a semicolon.
What makes this different?
Thanks,

[alpine]

simply put, it should not be placed before else and may not be placed before end. if it is placed before end it is simply an empty statement:

Code: Pascal  [Select][+][-]

1.   ...
2.   end
3.   ;
4. end
5. ;

[Thaddy]

if you put a ; semi column there the else will not be evaluated and it will not compile.
if else needs just a semi column after the else is fully evaluated.

[Warfley]

; is not a statement terminator it's a statement separator. So you only need it to separate multiple statements.
The if-then-else statement is defined as

Code: XML  [Select][+][-]

1. if <CONDITION> then <STATEMENT> else <Statement>

meaning between the then and the else only one statement is allowed. And because you can't have multiple statements, you can't have a semicolon. You have one in the end after the last statement, but this is not to terminate the else statement, but the if-then-else statement, because it is in a begin-end block that does allow for multiple statements delimited by semicolons.

This also means that you don't need any semicolons before an end:

Code: Pascal  [Select][+][-]

1. begin
2.   WriteLn('Hello World') // No semicolon here
3. end;

Because you only have one statement, you don't need a statement seperator. So you could reduce your code to:

Code: Pascal  [Select][+][-]

1. if (i >= 1) and (i<= 7) then
2.   begin
3.     if sw= 'Full' then
4.       writeln('The day in words is: ' + tmpStr)
5.     else
6.      writeln('The day in words is: ' + leftStr(tmpStr,3))
7.   end
8. end;

[Paolo]

Strictly speaking you can reduce further the code removing "begin-end" pair (even if the presence of begin-end makes the code more readable and less ambiguos).

Code: Pascal  [Select][+][-]

1. if (i >= 1) and (i<= 7) then
2.     if sw= 'Full' then
3.       writeln('The day in words is: ' + tmpStr)
4.     else
5.       writeln('The day in words is: ' + leftStr(tmpStr,3));  //very likely here you need ";"
6.  
7.  

[cousinp]

Thank you everyone.
Paul