CCalcEngine - Windows Calculator

Overview

The CCalcEngine class is the calculation engine that processes mathematical operations, maintains state, and performs infinite precision arithmetic using the RatPack library.

Constructor

fPrecedence

bool

required

Enable order of operations precedence (true for Scientific/Programmer, false for Standard)

fIntegerMode

bool

required

Restrict to integer-only calculations (true for Programmer mode)

pResourceProvider

IResourceProvider*

required

Provider for localized strings and resources

pCalcDisplay

ICalcDisplay*

Optional display callback interface

pHistoryDisplay

std::shared_ptr<IHistoryDisplay>

Optional history display interface

CCalcEngine(
    bool fPrecedence,
    bool fIntegerMode,
    CalculationManager::IResourceProvider* const pResourceProvider,
    __in_opt ICalcDisplay* pCalcDisplay,
    __in_opt std::shared_ptr<IHistoryDisplay> pHistoryDisplay
);

Example

#include "CalcEngine.h"

IResourceProvider* resources = GetResourceProvider();
ICalcDisplay* display = new MyDisplay();
auto history = std::make_shared<MyHistoryDisplay>();

// Create Scientific mode engine
CCalcEngine* sciEngine = new CCalcEngine(
    true,      // Enable precedence
    false,     // Not integer mode
    resources,
    display,
    history
);

// Create Programmer mode engine
CCalcEngine* progEngine = new CCalcEngine(
    true,      // Enable precedence
    true,      // Integer mode
    resources,
    display,
    nullptr    // No history in programmer mode
);

Initialization

InitialOneTimeOnlySetup()

Initializes shared global variables. Must be called once before creating any engine instances.

resourceProvider

IResourceProvider&

required

Resource provider for loading engine strings

static void InitialOneTimeOnlySetup(
    CalculationManager::IResourceProvider& resourceProvider
);

Example

IResourceProvider& resources = GetResourceProvider();
CCalcEngine::InitialOneTimeOnlySetup(resources);

Command Processing

ProcessCommand()

Processes a calculator command (digit, operator, function, etc.).

wID

OpCode

required

The operation code to execute

void ProcessCommand(OpCode wID);

Example

// Calculate 5 + 3
engine->ProcessCommand(IDC_5);
engine->ProcessCommand(IDC_PLUS);
engine->ProcessCommand(IDC_3);
engine->ProcessCommand(IDC_EQU);

Display and Error Handling

DisplayError()

Displays an error message to the user.

nError

uint32_t

required

Error code (e.g., CALC_E_DOMAIN for invalid input)

void DisplayError(uint32_t nError);

FInErrorState()

Checks if the calculator is currently in an error state.

return

bool

True if in error state, false otherwise

bool FInErrorState();

FInRecordingState()

Checks if the engine is recording input (building an expression).

return

bool

True if recording, false if displaying a result

bool FInRecordingState();

IsInputEmpty()

Checks if the current input is empty.

return

bool

True if input is empty or contains only “0”

bool IsInputEmpty();

Memory Operations

PersistedMemObject() - Get

Retrieves the persisted memory object.

return

std::unique_ptr<CalcEngine::Rational>

The current memory value as a Rational number

std::unique_ptr<CalcEngine::Rational> PersistedMemObject();

PersistedMemObject() - Set

Sets the persisted memory object.

memObject

CalcEngine::Rational const&

required

The memory value to persist

void PersistedMemObject(CalcEngine::Rational const& memObject);

Example

// Store current value in memory
engine->ProcessCommand(IDC_STORE);
auto memValue = engine->PersistedMemObject();

// Later, restore the memory value
engine->PersistedMemObject(*memValue);
engine->ProcessCommand(IDC_RECALL);

Precision and Radix

ChangePrecision()

Changes the calculation precision.

precision

int32_t

required

Number of digits of precision (16 for Standard, 32 for Scientific, 64 for Programmer)

void ChangePrecision(int32_t precision);

Note: This method also updates internal constants based on the new precision.

GetCurrentRadix()

Gets the current number base.

return

uint32_t

The current radix (2, 8, 10, or 16)

uint32_t GetCurrentRadix();

UpdateMaxIntDigits()

Updates the maximum integer digits based on current radix and word width.

void UpdateMaxIntDigits();

Display Formatting

GetCurrentResultForRadix()

Gets the current result formatted in a specific radix.

radix

uint32_t

required

The radix to format in (2, 8, 10, or 16)

precision

int32_t

required

Number of digits of precision

groupDigitsPerRadix

bool

required

Whether to group digits with separators

return

std::wstring

Formatted string representation

std::wstring GetCurrentResultForRadix(
    uint32_t radix,
    int32_t precision,
    bool groupDigitsPerRadix
);

GroupDigitsPerRadix()

Groups digits in a number string according to radix conventions.

numberString

std::wstring_view

required

The number string to format

radix

uint32_t

required

The radix (2, 8, 10, or 16)

return

std::wstring

Formatted string with digit grouping

std::wstring GroupDigitsPerRadix(
    std::wstring_view numberString,
    uint32_t radix
);

Grouping rules:

Decimal (10): Groups of 3 digits (e.g., “1,234,567”)
Binary (2): Groups of 4 bits (e.g., “1010 1100”)
Octal (8): Groups of 3 digits
Hexadecimal (16): Groups of 4 digits

GetStringForDisplay()

Converts a Rational number to a display string.

rat

CalcEngine::Rational const&

required

The rational number to convert

radix

uint32_t

required

The radix to display in

return

std::wstring

String representation of the number

std::wstring GetStringForDisplay(
    CalcEngine::Rational const& rat,
    uint32_t radix
);

DecimalSeparator()

Gets the decimal separator character.

return

wchar_t

The decimal separator character (e.g., ’.’ or ’,‘)

wchar_t DecimalSeparator() const;

Trigonometry

IsCurrentTooBigForTrig()

Checks if the current value exceeds the maximum safe value for trigonometric functions.

return

bool

True if value is too large, false otherwise

bool IsCurrentTooBigForTrig();

Note: Trigonometric functions lose accuracy for very large input values.

History

GetHistoryCollectorCommandsSnapshot()

Gets a snapshot of expression commands for history display.

return

std::vector<std::shared_ptr<IExpressionCommand>>

Vector of expression commands

std::vector<std::shared_ptr<IExpressionCommand>> GetHistoryCollectorCommandsSnapshot() const;

String Utilities

GetString()

Gets a localized string by ID.

ids

int

required

String resource ID

return

std::wstring_view

The localized string

static std::wstring_view GetString(int ids);

GetString() - by name

ids

std::wstring_view

required

String resource name

static std::wstring_view GetString(std::wstring_view ids);

OpCodeToString()

Converts an operation code to its string representation.

nOpCode

int

required

The operation code

return

std::wstring_view

String representation (e.g., ”+”, ”×”, “sin”)

static std::wstring_view OpCodeToString(int nOpCode);

OpCodeToUnaryString()

Converts a unary operation to its string representation.

nOpCode

int

required

The operation code

fInv

bool

required

Whether inverse function is active

angletype

AngleType

required

Current angle type (Degrees, Radians, Gradians)

static std::wstring_view OpCodeToUnaryString(
    int nOpCode,
    bool fInv,
    AngleType angletype
);

OpCodeToBinaryString()

Converts a binary operation to its string representation.

nOpCode

int

required

The operation code

isIntegerMode

bool

required

Whether in integer mode

static std::wstring_view OpCodeToBinaryString(
    int nOpCode,
    bool isIntegerMode
);

Enumerations

NUM_WIDTH

Defines word size for programmer mode.

enum class NUM_WIDTH {
    QWORD_WIDTH,  // 64 bits (default)
    DWORD_WIDTH,  // 32 bits
    WORD_WIDTH,   // 16 bits
    BYTE_WIDTH    // 8 bits
};

NumberFormat

Defines number formatting styles.

enum class NumberFormat {
    Float,         // Floating point or exponential if too large
    Scientific,    // Always scientific notation (e.g., 1.23e+10)
    Engineering    // Engineering notation (exponent multiple of 3)
};

AngleType

Defines angle units for trigonometric functions.

enum class AngleType {
    Degrees,   // 360 degrees per revolution
    Radians,   // 2π radians per revolution
    Gradians   // 400 gradians per revolution
};

Internal State

The engine maintains:

Current value (m_currentVal): Currently displayed number
Last value (m_lastVal): Left operand of pending operation
Hold value (m_holdVal): For repetitive calculations (pressing ”=” multiple times)
Parenthesis stack (m_parenVals): Values saved when opening parentheses
Precedence stack (m_precedenceVals): Values for order of operations
Operation state: Current and previous operations, flags for inverse, error, etc.

Core Components

ViewModels

Unit Conversion

Graphing

​Overview

​Constructor

​Example

​Initialization

​InitialOneTimeOnlySetup()

​Example

​Command Processing

​ProcessCommand()

​Example

​Display and Error Handling

​DisplayError()

​FInErrorState()

​FInRecordingState()

​IsInputEmpty()

​Memory Operations

​PersistedMemObject() - Get

​PersistedMemObject() - Set

​Example

​Precision and Radix

​ChangePrecision()

​GetCurrentRadix()

​UpdateMaxIntDigits()

​Display Formatting

​GetCurrentResultForRadix()

​GroupDigitsPerRadix()

​GetStringForDisplay()

​DecimalSeparator()

​Trigonometry

​IsCurrentTooBigForTrig()

​History

​GetHistoryCollectorCommandsSnapshot()

​String Utilities

​GetString()

​GetString() - by name

​OpCodeToString()

​OpCodeToUnaryString()

​OpCodeToBinaryString()

​Enumerations

​NUM_WIDTH

​NumberFormat

​AngleType

​Internal State

​See Also

Build docs developers (and LLMs) love

Overview

Constructor

Example

Initialization

InitialOneTimeOnlySetup()

Example

Command Processing

ProcessCommand()

Example

Display and Error Handling

DisplayError()

FInErrorState()

FInRecordingState()

IsInputEmpty()

Memory Operations

PersistedMemObject() - Get

PersistedMemObject() - Set

Example

Precision and Radix

ChangePrecision()

GetCurrentRadix()

UpdateMaxIntDigits()

Display Formatting

GetCurrentResultForRadix()

GroupDigitsPerRadix()

GetStringForDisplay()

DecimalSeparator()

Trigonometry

IsCurrentTooBigForTrig()

History

GetHistoryCollectorCommandsSnapshot()

String Utilities

GetString()

GetString() - by name

OpCodeToString()

OpCodeToUnaryString()

OpCodeToBinaryString()

Enumerations

NUM_WIDTH

NumberFormat

AngleType

Internal State

See Also