if then else syntax

[waltfair]

What is wrong with this snippet of code?
The compiler complains "; expected but ELSE found."

Code: Pascal  [Select][+][-]

1.  if(i>= Length(s))then t:=s;
2.   else
3. begin
4. t:= Copy(s,1,i);
5. s:= Copy(s,i+1,Length(s)-i);
6. end;
7. Firstword:= t;
8. end;
9.  

[eljo]

What is wrong with this snippet of code?
The compiler complains "; expected but ELSE found."

Code: Pascal  [Select][+][-]

1.  if(i>= Length(s))then t:=s;
2.   else
3. begin
4. t:= Copy(s,1,i);
5. s:= Copy(s,i+1,Length(s)-i);
6. end;
7. Firstword:= t;
8. end;
9.  

Code: Pascal  [Select][+][-]

1.  if(i>= Length(s))then t:=s//;<--- this semicolon is wrong.
2.   else
3. begin
4. t:= Copy(s,1,i);
5. s:= Copy(s,i+1,Length(s)-i);
6. end;
7. Firstword:= t;
8. end;
9.  

[Kays]

[In addition to eljo’s reply, some explanation:] Remember that in Pascal the semicolon is a statement separator, not a terminator like in many other programming languages.The if statement is composed of

• if
• Boolean expression
• then
• statement
• plus (optional) else and
• statement.

Note, it says statement (singular), not statements (plural). Thus you have t:=s as one statement. A second statement (properly separated by ;) as part of the then branch is not allowed according to the syntax repeated above.

[Paolo]

this compile, even if it looks strange

Code: Pascal  [Select][+][-]

1.   repeat
2.     if condition1 then
3.   until condition2;
4.  

no statement after then (or better hidden no-statement without ";").

[440bx]

As @Kays pointed out, semicolon in Pascal is a statement separator (with one exception in Delphi and FPC), this means that "else" cannot be preceded by a semicolon because "else" is not a statement.

this compile, even if it looks strange

Code: Pascal  [Select][+][-]

1.   repeat
2.     if condition1 then
3.   until condition2;
4.  

no statement after then (or better hidden no-statement without ";").

the "repeat until" pair also includes the compound statement functionality (that's why it does not require a "begin/end" pair to apply to multiple statements.)  Because of this, the following also compiles:

Code: Pascal  [Select][+][-]

1.   repeat
2.     if condition1 then ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
3.   until condition2;
4.  

where each semicolon separates an empty statement (there is an empty statement after the "then".)  The example could have also been written as: 

Code: Pascal  [Select][+][-]

1.   repeat
2.     if condition1 then begin end
3.   until condition2;
4.  

and adding semicolons after the "end" would have the same effect (which is none) as in the previous example.


I find terminators instead of separators easier to understand.

[Paolo]

Yes I know.
But in case I write such code, I prefer to add either ';' or empty 'begin..end' just for better readability and make clearer the code intention (intentional empty statement, no code mistake).

[440bx]

But in case I write such code, I prefer to add either ';' or empty 'begin..end' just for better readability and make clearer the code intention (intentional empty statement, no code mistake).

I do too.  I normally use a lone semicolon to indicate an empty statement.

[jamie]

Yes I know.
But in case I write such code, I prefer to add either ';' or empty 'begin..end' just for better readability and make clearer the code intention (intentional empty statement, no code mistake).

C/C++ programmers!