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amoradell's solution

to Wordy in the Delphi Pascal Track

Published at Jul 13 2018 · 1 comment
Instructions
Test suite
Solution

Parse and evaluate simple math word problems returning the answer as an integer.

Iteration 0 β€” Numbers

Problems with no operations simply evaluate to the number given.

What is 5?

Evaluates to 5.

Iteration 1 β€” Addition

Add two numbers together.

What is 5 plus 13?

Evaluates to 18.

Handle large numbers and negative numbers.

Iteration 2 β€” Subtraction, Multiplication and Division

Now, perform the other three operations.

What is 7 minus 5?

2

What is 6 multiplied by 4?

24

What is 25 divided by 5?

5

Iteration 3 β€” Multiple Operations

Handle a set of operations, in sequence.

Since these are verbal word problems, evaluate the expression from left-to-right, ignoring the typical order of operations.

What is 5 plus 13 plus 6?

24

What is 3 plus 2 multiplied by 3?

15 (i.e. not 9)

Iteration 4 β€” Errors

The parser should reject:

  • Unsupported operations ("What is 52 cubed?")
  • Non-math questions ("Who is the President of the United States")
  • Word problems with invalid syntax ("What is 1 plus plus 2?")

Bonus β€” Exponentials

If you'd like, handle exponentials.

What is 2 raised to the 5th power?

32

Testing

In order to run the tests for this track, you will need to install DUnitX. Please see the installation instructions for more information.

Loading Exercises into Delphi

If Delphi is properly installed, and *.dpr file types have been associated with Delphi, then double clicking the supplied *.dpr file will start Delphi and load the exercise/project. control + F9 is the keyboard shortcut to compile the project or pressing F9 will compile and run the project.

Alternatively you may opt to start Delphi and load your project via. the File drop down menu.

When Questions Come Up

We monitor the Pascal-Delphi support room on gitter.im to help you with any questions that might arise.

Submitting Exercises

Note that, when trying to submit an exercise, make sure the exercise file you're submitting is in the exercism/delphi/<exerciseName> directory.

For example, if you're submitting ubob.pas for the Bob exercise, the submit command would be something like exercism submit <path_to_exercism_dir>/delphi/bob/ubob.pas.

Source

Inspired by one of the generated questions in the Extreme Startup game. https://github.com/rchatley/extreme_startup

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you may receive assistance from a mentor.

uWordyTests.pas

unit uWordyTests;

interface
uses
  DUnitX.TestFramework;

const
  CanonicalVersion = '1.5.0';

type

  [TestFixture]
  WordyTests = class(TObject)
  public
//   [Ignore('Comment the "[Ignore]" statement to run the test')]
   [TestCase('a number', 'What is 5?,5')]
   procedure just_a_number(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('addition', 'What is 1 plus 1?,2')]
   procedure Addition(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('more addition', 'What is 53 plus 2?,55')]
   procedure More_Addition(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('addition with negative numbers', 'What is -1 plus -10?,-11')]
   procedure Addition_with_negative_numbers(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('large addition', 'What is 123 plus 45678?,45801')]
   procedure Large_addition(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('subtraction', 'What is 4 minus -12?,16')]
   procedure Subtraction(const aInput: string; aExpected: integer);

   [Ignore]
   [TestCase('multiplication', 'What is -3 multiplied by 25?,-75')]
   procedure Multiplication(const aInput: string; aExpected: integer);

   [Ignore]
   [TestCase('division', 'What is 33 divided by -3?,-11')]
   procedure Division(const aInput: string; aExpected: integer);

   [Ignore]
   [TestCase('multiple additions', 'What is 1 plus 1 plus 1?,3')]
   procedure Multiple_additions(const aInput: string; aExpected: integer);

   [Ignore]
   [TestCase('addition and subtraction', 'What is 1 plus 5 minus -2?,8')]
   procedure Addition_and_subtraction(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('multiple subtraction', 'What is 20 minus 4 minus 13?,3')]
   procedure Multiple_subtraction(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('subtraction then addition', 'What is 17 minus 6 plus 3?,14')]
   procedure Subtraction_then_addition(const aInput: string; const aExpected: integer);

   [Ignore]
   [TestCase('multiple multiplication', 'What is 2 multiplied by -2 multiplied by 3?,-12')]
   procedure Multiple_multiplication(const aInput: string; aExpected: integer);

   [Ignore]
   [TestCase('addition and multiplication', 'What is -3 plus 7 multiplied by -2?,-8')]
   procedure Addition_and_multiplication(const aInput: string; aExpected: integer);

   [Ignore]
   [TestCase('multiple division', 'What is -12 divided by 2 divided by -3?,2')]
   procedure Multiple_division(const aInput: string; aExpected: integer);

   [Ignore]
   [TestCase('unknown operation', 'What is 52 cubed?,unknown operation')]
   procedure Unknown_operation(const aInput: string; aExpected: string);

   [Ignore]
   [TestCase('Non math question', 'Who is the President of the United States?,unknown operation')]
   procedure Non_math_question(const aInput: string; aExpected: string);

   [Ignore]
   [TestCase('reject problem missing an operand', 'What is 1 plus?,syntax error')]
   procedure problem_missing_an_operand(const aInput: string; aExpected: string);

   [Ignore]
   [TestCase('reject problem with no operands or operators', 'What is?,syntax error')]
   procedure problem_with_no_operands_or_operators(const aInput: string; aExpected: string);

   [Ignore]
   [TestCase('reject two operations in a row', 'What is 1 plus plus 2?,syntax error')]
   procedure reject_two_operations_in_a_row(const aInput: string; aExpected: string);

   [Ignore]
   [TestCase('reject two numbers in a row', 'What is 1 plus 2 1?,syntax error')]
   procedure reject_two_numbers_in_a_row(const aInput: string; aExpected: string);

   [Ignore]
   [TestCase('reject postfix notation', 'What is 1 2 plus?,syntax error')]
   procedure reject_postfix_notation(const aInput: string; aExpected: string);

   [Ignore]
   [TestCase('reject prefix notation', 'What is plus 1 2?,syntax error')]
   procedure reject_prefix_notation(const aInput: string; aExpected: string);
  end;

implementation
uses uWordy;

procedure WordyTests.Addition(const aInput: string; const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Addition_and_multiplication(const aInput: string;
  aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Addition_and_subtraction(const aInput: string;
  const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Addition_with_negative_numbers(const aInput: string;
  const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Division(const aInput: string; aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.problem_missing_an_operand(const aInput: string;
  aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

procedure WordyTests.just_a_number(const aInput: string;
  const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Large_addition(const aInput: string;
  const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.More_Addition(const aInput: string;
  const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Multiple_additions(const aInput: string;
  aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Multiple_division(const aInput: string;
  aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Multiple_multiplication(const aInput: string;
  aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Multiple_subtraction(const aInput: string;
  const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Multiplication(const aInput: string; aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Subtraction(const aInput: string; aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Subtraction_then_addition(const aInput: string;
  const aExpected: integer);
begin
  Assert.AreEqual(aExpected, TWordy.Answer(aInput));
end;

procedure WordyTests.Unknown_operation(const aInput: string; aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

procedure WordyTests.problem_with_no_operands_or_operators(const aInput: string; aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

procedure WordyTests.Non_math_question(const aInput: string; aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

procedure WordyTests.reject_postfix_notation(const aInput: string;
  aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

procedure WordyTests.reject_prefix_notation(const aInput: string;
  aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

procedure WordyTests.reject_two_numbers_in_a_row(const aInput: string;
  aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

procedure WordyTests.reject_two_operations_in_a_row(const aInput: string;
  aExpected: string);
var MyProc: TTestLocalMethod;
begin
  MyProc := procedure
            begin
              TWordy.Answer(aInput);
            end;

  Assert.WillRaiseWithMessage(MyProc, EInvalidProblem, aExpected);
end;

initialization
  TDUnitX.RegisterTestFixture(WordyTests);
end.
unit uWordy;

interface
uses
  System.Sysutils, System.Generics.Collections;

type
  TArithmeticOp = TFunc<integer, integer, integer>;
  TOperatorDict = TDictionary<string, TArithmeticOp>;

  TWordy = class
  private
    class var
      FNbOperands: integer;
      FNbOperators: integer;
      FOperators: TOperatorDict;
      FWords: TArray<string>;
    class procedure BuildOperators;
    class function IsValid(aInput: string): boolean;
  public
    class function Answer(aInput: string): integer;

  end;

  EInvalidProblem = class(Exception);

implementation

class procedure TWordy.BuildOperators;
begin
  FOperators := TOperatorDict.create;
  FOperators.Add('plus',
    function(op1, op2: integer): integer
    begin
      result := op1 + op2
    end);
  FOperators.Add('minus',
    function(op1, op2: integer): integer
    begin
      result := op1 - op2
    end);
  FOperators.Add('multiplied',
    function(op1, op2: integer): integer
    begin
      result := op1 * op2
    end);
  FOperators.Add('divided',
    function(op1, op2: integer): integer
    begin
      result := op1 div op2
    end);
end;

class function TWordy.IsValid(aInput: string): boolean;
var
  i: integer;
begin
  aInput := StringReplace(aInput, ' by ', ' ', [rfReplaceAll]);
  FWords := copy(aInput, 1, length(aInput) - 1).Split([' ']);
  FNbOperands := 0;
  FNbOperators := 0;
  BuildOperators;
  for i := 2 to High(FWords) do
  begin
    if (StrToIntDef(FWords[i], 0) <> 0) then
      inc(FNbOperands)
    else if (FOperators.ContainsKey(FWords[i])) then
      inc(FNbOperators);
  end;
  result := not ((FNbOperands < 2) or (FNbOperators < 1) or (FNbOperands - FNbOperators <> 1));
end;

class function TWordy.Answer(aInput: string): integer;
var
  zFunc, zFunc2: TArithmeticOp;
begin
  if not IsValid(aInput) then
    raise EInvalidProblem.Create('Invalid Problem');

  zFunc := FOperators[FWords[3]];
  if (FNbOperators = 1) then
    result := zFunc(StrToInt(FWords[2]), StrToInt(FWords[4]))
  else
  begin
    zFunc2 := FOperators[FWords[5]];
    result := zFunc2(zFunc(StrToInt(FWords[2]), StrToInt(FWords[4])),
      StrToInt(FWords[6]));
  end;
end;

end.

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of rpottsoh

@amoradell looks good. Thanks for going the extra mile. Let me know if you need help on the other two exercises you are working on. Feel free to submit what you have and describe what your issues are; what is hanging you up.

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
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