Binary and linear search methods for a number-guessing game

Question

This is a code written is Pascal (Delphi). It asks the user to think of a number between min_ and max_ and then guesses the number using either a Binary or a Linear method.

 program BandLSearch;
 {$APPTYPE CONSOLE}
 {$R *.res}
 uses
 System.SysUtils;
 var
 min_, max_: integer; // set the max and min to check between the two (inclusive)
 BinorLin: string; // Get user input as to which method they wish to use
 procedure Linear();
 {
 This uses a linear search technique to guess the number.
 It will ask min_ then min_ +1 etc up to max_. e.g. 1, 2, 3, ... , 99, 100
 }
 var
 input: string;
 count: integer; // For the foor loop
 begin
 for count := min_ to max_ do // loop from min to max and ask if the number is corect, one by one
 begin
 write('Is your number ',count,'? Y or N? > ');
 readln(input);
 if (input = 'Y') or (input = 'y') then
 begin
 writeln('Found your number, it is ',count);
 readln; // Prevent the code ending without being able to read the output.
 break
 end
 else
 begin
 if count = max_ then //If they have reached max and not said yes, they are lying
 begin
 writeln('You have cheated');
 readln;
 end;
 end;
 end;
 end;
 procedure Binary();
 {
 This uses a linear search technique to guess the number
 It will ask (min_ + max_)/2 and the user says too high or too low.
 Depending on the response, it will set either min_ or max_ to the guessed number
 Eventually it narrows down, eg:
 50, 75, 62, 68, 65, 63, 64
 L H L H H L C
 }
 var
 input: string;
 guess, preGuess: integer; // For the current computer guess
 goesTaken : integer; // To monitor the guesses needed
 end_: integer; // Will increase for each guess that max_ = min_
 begin
 preGuess := -1; // Will not be the guess.
 goesTaken := 0;
 end_ := 0;
 while end_ < 2 do //when it is 2, it will have guessed all the numbers.
 begin
 inc(goesTaken);
 guess := (max_ + min_) div 2;
 writeln('Is your number ',guess,'?');
 writeln('If guess is too high enter H, if it''s too low, enter L.');
 write('If the guess is corect, enter C > ');
 readln(input);
 if input = 'H' then // Number is too high, so guess lower
 max_ := guess - 1
 else
 if input = 'L' then // Number is too low, so guess higher
 min_ := guess + 1
 else // Number is correct
 begin
 writeln('Found your number, it is ',guess);
 writeln('It took me ',goesTaken,' goes.');
 readln;
 break
 end;
 if guess = preGuess then // If the computer asks the same number two times in a row, the user has cheated.
 begin
 writeln('You have cheated');
 readln;
 break
 end
 else
 preGuess := guess;
 if (max_ = min_) then // If min is the same as max, then 1 go later the code can exit.
 begin
 end_ := end_ + 1;
 end;
 end;
 end;
 begin
 min_ := 0;
 max_ := 100;
 writeln('Think of a number between ',min_, ' and ', max_, '. I will guess it.');
 write('Do you want to use a (l)inear or a (b)inary search? > ');
 readln(BinorLin);
 if BinorLin = 'l' then // User input comparison
 begin
 writeln('Starting Linear Search...');
 Linear();
 end
 else;
 begin
 if BinorLin = 'b' then
 begin
 writeln('Starting Binary Search...');
 Binary();
 end
 else // didn't enter 'l' or 'b'
 begin
 exit
 end;
 end; 
 end.

This is a high school assignment, however I have already handed it in (today) for marking. I'd be interested in the opinion of more than my teacher.

Answer 1

• I would rather use Free Pascal than Delphi, makes code more promptly editable;
• You should avoid nested if's, specially in pascal, where you can easily get lost otherwise. Use the case statement instead.
• pascal do not use camelCase but PascalCase.
• you should use const for constants, and name them like PASCAL_CONSTANT.
• you should prefix your own variables to avoid getting lost in terms of scope and variables types:
  • F for class fields;
  • T for objects;
  • A for property (generic) values;
  • I for integers, for local variables
  • S for strings, for local variables
  • and so on
• starting code messages should be put at the starting of the code, i.e., first line after a begin statement of the corresponding procedure, function or program.
• It is not necessary to write the () for methods that does not require entries.
• Pascal is case insensitive. However, it does not mean you should not be consistent with existing code: you should use WriteLn, instead writeln, for example.

Putting all together:

program BandLSearch;
uses SysUtils;
var
 SInput: string; // Get user input as to which method they wish to use
const // set the max and min to check between the two (inclusive)
 MIN_VALUE : integer = 0;
 MAX_VALUE : integer = 100;
{ This uses a linear search technique to guess the number.
 It will ask MIN_VALUE then MIN_VALUE +1 up to MAX_VALUE. e.g. 1, 2, 3, ... , 99, 100 }
procedure Linear;
var
 ICount: integer; // For the foor loop
begin
 WriteLn('Starting Linear Search...');
 for ICount := MIN_VALUE to MAX_VALUE do // loop from min to max and ask if the number is corect, one by one
 begin
 Write('Is your number ',ICount,'? Y or N? > ');
 ReadLn(SInput);
 SInput := UpperCase(SInput);
 if SInput = 'Y' then
 begin
 WriteLn('Found your number, it is ',ICount);
 ReadLn; // Prevent the code ending without being able to read the output.
 Break
 end;
 if ICount = MAX_VALUE then //If they have reached max and not said yes, they are lying
 begin
 WriteLn('You have cheated.');
 ReadLn;
 end;
 end;
end;
{ This uses a binary search technique to guess the number
 It will ask (MIN_VALUE + MAX_VALUE)/2 and the user says too high or too low.
 Depending on the response, it will set either MIN_VALUE or MAX_VALUE to the guessed number
 Eventually it narrows down, eg:
 50, 75, 62, 68, 65, 63, 64
 L H L H H L C }
procedure Binary;
var
 IGuess, IPreGuess, // For the current computer guess
 IGoesTaken, // To monitor the guesses needed
 IEnd: integer; // Will increase for each guess that MAX_VALUE = MIN_VALUE
begin
 WriteLn('Starting Binary Search...');
 IPreGuess := -1; // Will not be the guess.
 IGoesTaken := 0;
 IEnd := 0;
 repeat
 Inc(IGoesTaken);
 IGuess := (MAX_VALUE + MIN_VALUE) div 2;
 WriteLn('Is your number ',IGuess,'?');
 WriteLn('If guess is too high enter H, if it''s too low, enter L.');
 Write('If the guess is correct, enter C or Y > ');
 ReadLn(SInput);
 SInput := UpperCase(SInput);
 case SInput of 
 'H': MAX_VALUE := IGuess - 1; // Number is too high, so guess lower
 'L': MIN_VALUE := IGuess + 1; // Number is too low, so guess higher
 'C', 'Y':
 begin
 WriteLn('Found your number, it is ',IGuess);
 WriteLn('It took me ',IGoesTaken,' goes.');
 ReadLn;
 Break;
 end;
 else // Number is correct 
 end;
 if IGuess = IPreGuess then // If the computer asks the same number two times in a row, the user has cheated.
 begin
 WriteLn('Sorry, I did not undertand you (or you have cheated).');
 ReadLn;
 Break;
 end
 else
 IPreGuess := IGuess;
 if MAX_VALUE = MIN_VALUE then
 IEnd := IEnd + 1; // If min is the same as max, then 1 go later the code can exit.
 until IEnd >= 2;
end;
begin
 WriteLn('Think of a number between ',MIN_VALUE, ' and ', MAX_VALUE, '. I will guess it.');
 Write('Do you want to use a (l)inear or a (b)inary search? > ');
 ReadLn(SInput);
 SInput := LowerCase(SInput);
 case SInput of // User input comparison
 'l': Linear;
 'b': Binary;
 else
 Exit;
 end; 
end.

• cpicanco: FTA is common in Pascal, Free Pascal and Delphi. For local variables there are no standards, but you will frequently find S for local strings and I for loop integers. IS is an extension considering that fact.
• cpicanco: @holroy, after all, the point is not getting lost. Works for me :)
• holroy: I'm all for clarity in naming, but in C# or Python naming standards is used where you don't need prefixes, but rather use variations on camelCase or PascalCase or snake_case. And you should normally not have a problem knowing the type of a variable as that should be given by the name/context. The same applies for scope, as if your code is so long you don't have control of the scope you should add some procedures/methods/functions to narrow down the scope. But YMMV...
• cpicanco: For me works like that, PascalMethod, LPascalLocalVariable, AMethodValue, FFieldAttribute, TAbstractObject. As you can see, methods are not prefixed. But, again, for local variables there are no standards as far as I know.
• Tim: I will think about these. I essentially have to use Delphi but I'll consider the others. I especially like the use of case statements but I'm unsure the variable prefix is needed, and some of the other naming conventions seem strange. Thanks though.