Phase 2: Add documentation and tests for logical, comparison, and arithmetic converters

[Copilot]

Completes Phase 2 of converter audit (#225): comprehensive XML documentation and 130+ unit tests for 18 converters across logical, comparison, and arithmetic categories.

Changes

Documentation (18 converters)

Added Russian XML documentation with:

• Mathematical formulas and behavior descriptions
• ConvertBack support analysis with rationale
• XAML usage examples

Converters documented:

• Logical: And, Or, IsNaN, IsPositive, IsNegative, NANtoVisibility, Null2Visibility
• Comparison: GreaterThan, LessThan, GreaterThanOrEqual, LessThanOrEqual, InRange, OutRange
• Arithmetic: Addition, Subtraction, Multiply, Divide, Linear

Unit Tests (130+ tests)

Created comprehensive test coverage:

• Basic functionality and edge cases (NaN, Infinity, boundaries)
• ConvertBack behavior validation
• Russian XML test documentation per project standards

Example documentation:

/// <summary>Конвертер сравнения "больше чем"</summary>
/// <remarks>
/// <para><b>Формула:</b> result = value &gt; Value</para>
/// <para><b>ConvertBack:</b> Не поддерживается, так как невозможно восстановить конкретное число из булевого значения.
/// Результат <c>true</c> может означать любое число больше порога.</para>
/// </remarks>
/// <example>
/// <code language="xaml">
/// &lt;Button IsEnabled="{Binding Count, Converter={converters:GreaterThan Value=100}}" /&gt;
/// </code>
/// </example>
public class GreaterThan(double value) : DoubleToBool { ... }

ConvertBack Analysis

Category	ConvertBack Support
Arithmetic (Addition, Subtraction)	✅ Fully reversible
Arithmetic (Multiply, Divide, Linear)	✅ Reversible when K ≠ 0
Logical (And, Or)	❌ Multi-input ambiguity
Checks (IsNaN, IsPositive, IsNegative)	❌ Information loss
Comparison (GreaterThan, LessThan, etc.)	❌ Information loss
Visibility (NANtoVisibility, Null2Visibility)	❌ Information loss
Range (InRange, OutRange)	❌ Information loss

Metrics

• 18 converters audited
• 130+ tests created
• ~2,200 LOC added

Original prompt

🎯 Master Issue: Complete Audit and Improvement of MathCore.WPF Converters

This is a master tracking issue for the comprehensive audit and improvement work on all value converters in MathCore.WPF library.

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📊 Overall Progress

Phase	Status	Converters	Tests	Coverage	Documentation
Phase 1	✅ DONE	16/16	121/121	~35%	~50%
Phase 2	🔄 In Progress	0/~20	0	-	-
Phase 3	⏳ Planned	-	-	-	-
TOTAL	🔄 16%	16/~100	121	~35%	~50%

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✅ Phase 1: Critical Math Converters - COMPLETED

Issue: #223
Status: ✅ DONE
Tests: 121/121 passing ✅
Time spent: ~8 hours

Fixed Converters (16):

1. ✅ Abs - |x| → NotSupportedException (ambiguous: ±a)
2. ✅ Sin, Cos, Tan, Ctg - Periodic functions → NotSupportedException
3. ✅ Sign, SignValue - Loses magnitude → NotSupportedException
4. ✅ Round, Truncate, Trunc, RoundAdaptive - Loses precision → NotSupportedException
5. ✅ Inverse - 1/x → ConvertBack WORKS (involution) ⭐
6. ✅ Mod - x % M → NotSupportedException (loses quotient)
7. ✅ dB - Amplitude ↔ Decibels → ConvertBack WORKS (log ↔ exp) ⭐
8. ✅ Not - boolean NOT → ConvertBack WORKS (involution) ⭐
9. ✅ IsNull - null check → NotSupportedException

Achievements:

• 🐛 Fixed 16 critical bugs in ConvertBack
• 📝 Added comprehensive XML documentation
• 🧪 Created 121 unit tests (100% passing)
• 📚 Documented 3 converters with working ConvertBack (Inverse, dB, Not)
• ⚠️ Documented breaking changes

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🔄 Phase 2: Logical & Comparison Converters - IN PROGRESS

Issue: #225
Status: 🔄 In Progress
Estimated time: 22-27 hours

Categories:

2.1 Logical Converters (Priority: HIGH)

• And, Or - MultiValueConverter
• IsNaN, IsPositive, IsNegative
• NANtoVisibility, Null2Visibility

Expected: ~50-70 tests

2.2 Comparison Converters (Priority: HIGH)

• GreaterThan, LessThan, Equal
• GreaterThanOrEqual, LessThanOrEqual
• InRange, OutRange

Expected: ~40-50 tests

2.3 Arithmetic Converters (Priority: MEDIUM - Verification)

• Addition, Subtraction ✅ (ConvertBack likely OK)
• Multiply, Divide ✅ (ConvertBack likely OK)
• Linear ✅ (ConvertBack likely OK)

Expected: ~30-40 tests (verification + edge cases)

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⏳ Phase 3: Specialized & Collection Converters - PLANNED

Status: ⏳ Planned
Estimated time: 15-20 hours

Categories:

3.1 Temperature & Unit Converters

• TemperatureC2F, TemperatureF2C ✅ (ConvertBack should work)
• Mapper ✅ (ConvertBack should work)

3.2 Visibility Converters

• Bool2Visibility (ConvertBack possible)
• Value2Visibility variants

3.3 Collection Converters

• ArrayElement, FirstItem, LastItem
• MultiValuesToEnumerable

3.4 String Converters

• ToString, ToUpper, ToLower
• JoinString, DataLengthString

3.5 Reflection Converters

• Assembly* converters (Title, Version, Copyright, etc.)
• GetType, GetTypeAssembly

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📈 Target Metrics

Current State (after Phase 1):

• ✅ Fixed converters: 16
• ✅ Unit tests: 121
• ✅ Code coverage: ~35%
• ✅ XML documentation: ~50%

Target State (after Phase 3):

• 🎯 Fixed converters: ~35-40
• 🎯 Unit tests: ~350
• 🎯 Code coverage: ≥80%
• 🎯 XML documentation: 100%

Progress Chart:

Phase 1: ████████████████░░░░░░░░ 35% Coverage
Phase 2: ████████████████████████░ 60% Coverage (target)
Phase 3: ████████████████████████████ 80% Coverage (target)

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🐛 Types of Issues Found

Critical Issues (Fixed in Phase 1):

1. Mathematical incorrectness - ConvertBack returning wrong values
2. Silent failures - No exceptions for impossible operations
3. Missing documentation - No explanation of behavior

Common Patterns:

Pattern	Count	Examples	Fix
Ambiguous inverse	7	Abs, Sin, Cos, Sign	NotSupportedException
Loses information	5	Round, Truncate, Mod	NotSupportedException
Works correctly	3	Inverse, dB, Not	Document + test
Needs verification	~15	Addition, Linear, etc.	Test + verify

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📝 Documentation Standards

Each converter must have:

1. Class Documentation:

/// <summary>Brief description</summary>
/// <remarks>
/// Detailed explanation of transformation logic
/// <para>Mathematical formula</para>
/// <para>ConvertBack behavior (supported/not supported + why)</para>
/// </remarks>
/// <example>
/// XAML usage examples
/// </example>

2. ConvertBack Documentation:

• If supported: Document behavior + add two-way binding tests
• If not supported: Explain mathematical reason + add regression test

3. XAML Examples:

• Simple usage
• With parameters
• Two-way binding (if supported)

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🧪 Testing Standards

Test Structure (per converter):

• ✅ Basic functionality: 5-1...

Issue created by Visual Studio Copilot

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