Chapter 06: Numbers, Math, and Truth

Why this chapter matters

Arithmetic is the simplest place to practice postfix reading because the stack effects are small: two numbers go in, one number comes out. Comparisons build on the same shape and leave booleans that later chapters use for conditionals.

What you will build

You will build a budget calculator and use it to learn numeric operations, comparisons, boolean helpers, checked conversions, and assertions.

Concepts in plain English

Ricochet has integer and float numeric values. Symbolic arithmetic words such as + and * are compact. Readable aliases such as add and multiply can make teaching code clearer.

Comparison words consume two values and leave true or false. Conversion words such as to_integer can fail, so they return Result values instead of pretending every string is a valid number.

Words introduced

Arithmetic and comparison words: +, add, -, subtract, *, multiply, /, divide, %, modulo, equals, =, not_equals?, !=, <, less_than?, >, greater_than?, <=, less_or_equals?, >=, and greater_or_equals?.

Helpers: negate, abs, min, max, clamp, not, and, or, assert, assert_true, assert_false, and assert_equals.

Conversions include to_number, to_integer, to_float, and size-specific integer and float conversions.

Guided example

Run the budget example:

bashrco run examples/learn/06-numbers-math-and-truth/budget.rco

The core calculation is ordinary postfix math:

ricochet$rent $food + spent var
$income $spent - remaining var
$remaining 0 > println

How to read the code

$rent $food + spent var reads the two named values, adds them, and names the result spent.

Checked conversions return Result values:

ricochet"42" to_integer dup ok? if
  value println
else
  error "kind" at println
end

The dup ok? if ... else ... end pattern keeps the original result below the condition so the chosen branch can unwrap either value or error.

Try it

Change income, rent, and food. Then add one assertion:

ricochet$remaining 57 assert_equals

If the value is wrong, the VM fails loudly. Assertions are useful in examples, tests, and small scripts where a wrong assumption should stop execution.

Check your understanding

• 1 2 + leaves 3.
• 1 2 < leaves true.
• "42" to_integer leaves a Result, not a bare integer.
• Use ok? before unwrapping a result whose input came from outside your control.

Common mistakes

• Ignoring Result values from conversions.
• Assuming mixed numeric operations never promote values. Integer plus float produces a float.
• Using truthy values where a precise comparison would explain intent.
• Forgetting that / with two integers stays integer division.

What you know now

You know how Ricochet handles everyday numeric work, truth checks, assertions, and checked conversions. Later host APIs use the same Result habit for recoverable failures.