Arithmetic & strings

• + : add numbers, or concatenate strings
• - : subtract numbers
• * : multiply numbers
• / : divide numbers
• % : remainder of division
• Playground

Arithmetic operators work on numbers, with the usual precedence (use parentheses to group). + also concatenates strings — but never mixes the two: string + number is a compile error (TF2004), not silent coercion.

Operator	Effect
+	add numbers, or concatenate strings
-	subtract numbers
*	multiply numbers
/	divide numbers
%	remainder of division

+ : add numbers, or concatenate strings

Between two numbers, adds. Between two strings, concatenates. Mixing a string and a number is TF2004 — convert explicitly with string(...) first.

total: item.price + item.tax
fullName: user.firstName + " " + user.lastName

- : subtract numbers

remaining: order.total - order.paid

* : multiply numbers

subtotal: item.price * item.quantity

/ : divide numbers

unitPrice: item.subtotal / item.quantity

% : remainder of division

isEvenQty: item.quantity % 2 == 0

Playground

Mapping✔Playground ↗

input item: { price: number, quantity: number, taxRate: number }

map {
  subtotal: item.price * item.quantity,
  tax: item.price * item.quantity * item.taxRate,
  total: item.price * item.quantity * (1 + item.taxRate),
  isEvenQty: item.quantity % 2 == 0,
}

input item: { price: number, quantity: number, taxRate: number } map { subtotal: item.price * item.quantity, tax: item.price * item.quantity * item.taxRate, total: item.price * item.quantity * (1 + item.taxRate), isEvenQty: item.quantity % 2 == 0, }

Input JSON

{ "price": 19.9, "quantity": 3, "taxRate": 0.2 }

{ "price": 19.9, "quantity": 3, "taxRate": 0.2 }

Output

{
  "subtotal": 59.699999999999996,
  "tax": 11.94,
  "total": 71.63999999999999,
  "isEvenQty": false
}

inferred type{ subtotal: number; tax: number; total: number; isEvenQty: boolean; }

This example is intentionally broken — + never coerces:

input order: { id: number }

map {
  label: "Order #" + order.id,
}

Mixed-type formatting goes through an explicit conversion — "Order #" + string(order.id) — or stays in your host language.

Next: Comparisons.