Human Readable Calculation Steps

A .NET library for arithmetic that explains itself. Every value carries a caption, every operator records its derivation, and the final result can be printed as the human-readable steps that produced it.

Useful for invoices, payroll, tax breakdowns, financial reports, or any UI where a number on screen needs to explain where it came from.

Install

dotnet add package Appify.HumanReadableCalculationSteps

Target framework: .NET 8.0.

Quick start

using HumanReadableCalculationSteps;

var a = 2m.As("a");
var b = 3m.As("b");
var c = 4m.As("c");

var result = (a + b) * c;

// result.Value                  -> 20
// result.FinalCalculationSteps  -> "(a[2] + b[3]) × c[4] = 20"

The × and ÷ symbols are emitted instead of * and /, and parentheses are inserted automatically where operator precedence demands them.

---

Features

Each section is one self-contained way to use the library, with a runnable example and the exact output you'd see in FinalCalculationSteps.

1. Captioning literals — .As(caption)

Attach a human-readable name to any decimal or int.

var price    = 100m.As("Price");
var quantity = 3.As("Quantity");

// price.FinalCalculationSteps    -> "Price = 100"
// quantity.FinalCalculationSteps -> "Quantity = 3"

2. Arithmetic operators with automatic precedence

+, -, *, / are overloaded. Multiplication/division have higher precedence than addition/subtraction, and parentheses are added to the rendered caption automatically when needed.

var a = 2m.As("a");
var b = 3m.As("b");
var c = 4m.As("c");

var sumThenTimes = (a + b) * c;
var timesThenSum = a * b + c;

// sumThenTimes.FinalCalculationSteps -> "(a[2] + b[3]) × c[4] = 20"
// timesThenSum.FinalCalculationSteps -> "a[2] × b[3] + c[4] = 10"

3. Naming intermediate results — .As("NewName") on a computed value

Wrap a sub-expression with a name and the trace expands into discrete, labeled steps.

var basePrice    = 200m.As("BasePrice");
var discountRate = 0.15m.As("DiscountRate");
var taxRate      = 0.08m.As("TaxRate");

var discount         = (basePrice * discountRate).As("Discount");
var discountedPrice  = (basePrice - discount).As("DiscountedPrice");
var tax              = (discountedPrice * taxRate).As("Tax");
var finalTotal       = (discountedPrice + tax).As("FinalTotal");

Console.WriteLine(finalTotal.FinalCalculationSteps);

Output:

Discount = BasePrice[200] × DiscountRate[0.15] = 30

DiscountedPrice = BasePrice[200] - Discount[30] = 170

Tax = DiscountedPrice[170] × TaxRate[0.08] = 13.6

FinalTotal = DiscountedPrice[170] + Tax[13.6] = 183.6

4. Capturing variable & property names — ValueWithCaption.From(expression)

Build a value from a lambda and the library will reflect on the expression tree to pick up the source variable / property name as the caption. Supports decimal, int, double, float.

var basePrice = 100m;
var rate      = 0.18m;

var price = ValueWithCaption.From(() => basePrice);
var tax   = ValueWithCaption.From(() => rate);

var taxAmount = price * tax;
// taxAmount.FinalCalculationSteps -> "basePrice[100] × rate[0.18] = 18"

Property and field references work the same way:

var product = new Product { Price = 99.99m };
var p = ValueWithCaption.From(() => product.Price);
// p.FinalCalculationSteps -> "Price"

5. [DisplayName] for human-friendly property captions

If a property is annotated with System.ComponentModel.DisplayNameAttribute, that label is used instead of the raw property name.

class Product
{
    [DisplayName("Product Cost")]
    public decimal Cost { get; set; }
}

var product = new Product { Cost = 150m };
var c = ValueWithCaption.From(() => product.Cost);
// c.FinalCalculationSteps -> "Product Cost"

6. LINQ-style Sum over collections

Two overloads, mirroring Enumerable.Sum: one for a projection, one for a direct collection of ValueWithCaption.

var employees = new[]
{
    new { Advance = 500m.As("Employee1Advance") },
    new { Advance = 750m.As("Employee2Advance") },
    new { Advance = 300m.As("Employee3Advance") },
};

var total = employees.Sum(e => e.Advance);
// total.FinalCalculationSteps
//   -> "Employee1Advance[500] + Employee2Advance[750] + Employee3Advance[300] = 1,550"

Expanded vs compact: with 1–3 items the trace lists each addend; with 4+ items it switches to a compact Sum(<commonName>, count(N)) form so traces stay readable on large collections.

var values = new[]
{
    100m.As("Value1"), 200m.As("Value2"),
    150m.As("Value3"), 250m.As("Value4"),
};

var total = values.Sum();
// total.FinalCalculationSteps -> "Sum(Value, count(4))[700] = 700"

Calculation steps from inner expressions are preserved when summing wrapped values:

var advance1 = (2000m.As("Salary1") * 0.25m.As("Rate")).As("Advance1");
var advance2 = (3000m.As("Salary2") * 0.30m.As("Rate")).As("Advance2");

var totalAdvances = new[] { advance1, advance2 }.Sum().As("TotalAdvances");

Output:

Advance1 = Salary1[2,000] × Rate[0.25] = 500

Advance2 = Salary2[3,000] × Rate[0.3] = 900

TotalAdvances = Advance1[500] + Advance2[900] = 1,400

7. Automatic multi-line formatting for long expressions

When an expression has more than three operators (or exceeds ~150 characters), the trace is broken across lines with aligned operators and indented sub-expressions, so long calculations stay legible.

var q1 = new[] { 1000m.As("Jan"), 1200m.As("Feb"),  900m.As("Mar") }.Sum();
var q2 = new[] { 1100m.As("Apr"), 1300m.As("May"), 1000m.As("Jun") }.Sum();
var q3 = new[] {  950m.As("Jul"), 1150m.As("Aug"), 1250m.As("Sep") }.Sum();

var halfYear = q1 + q2 + q3;

Output (note the aligned + column):

  Jan[1,000]
+ Feb[1,200]
+ Mar[900]
+ Apr[1,100]
+ May[1,300]
+ Jun[1,000]
+ Jul[950]
+ Aug[1,150]
+ Sep[1,250]
= 9,850

And with mixed operators and parentheses:

var groupA = new[] { 10m.As("A1"), 15m.As("A2") }.Sum();
var groupB = new[] { 20m.As("B1"), 25m.As("B2") }.Sum();
var groupC = new[] {  5m.As("C1"), 10m.As("C2") }.Sum();

var result = (groupA + groupB) * groupC - 50m.As("Deduction");

Output:

  (  A1[10]
   + A2[15]
   + B1[20]
   + B2[25]
  )
×
  (  C1[5]
   + C2[10]
  )
- Deduction[50]
= 1,000

8. Comparison operators

>, <, >=, <=, ==, != are overloaded — both between two ValueWithCaption and between a ValueWithCaption and a raw decimal. The library also implements IComparable and IComparable<ValueWithCaption>, so values can be sorted with LINQ's OrderBy.

var a = 10m.As("a");
var b = 5m.As("b");

bool gt        = a > b;        // true
bool gtDecimal = a > 7.5m;     // true

var sorted = new[] { a, b }.OrderBy(x => x).ToList();

Equality is value-based: a == b is true iff a.Value == b.Value, regardless of caption. This keeps ==, Equals, and CompareTo in agreement.

9. Static helpers — StaticValues.Zero, StaticValues.One

Convenience constants for use in folds and seeded reductions:

var total = items
    .Select(i => i.Amount.As("Amount"))
    .Aggregate(StaticValues.Zero, (acc, x) => acc + x);

10. Decimal formatting in output

FinalCalculationSteps runs every numeric token through a single formatting pass:

• Rounds to 2 decimal places
• Strips trailing zeros after the decimal point
• Inserts thousand separators (,)
• Drops the decimal point entirely when the value is an integer

Raw value	Rendered as
100m	100
1500m	1,500
1234.5m	1,234.5
1234.56789m	1,234.57
0.18m	0.18

11. CRLF-stable output

FinalCalculationSteps always emits CRLF (\r\n) line endings, regardless of host platform, so output is byte-stable across Windows, Linux, and macOS — handy for snapshot tests and reproducible reports.

---

Use case

The library exists for one job: making a calculation explain itself to a non-technical reader. Payroll slips, tax breakdowns, invoice reconciliations, audit reports — anywhere the user looks at a final number and asks "how did you get this?", you can hand them FinalCalculationSteps.

License

See LICENSE.

Collaboration by Claude