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Formula verification and errors

Updated 2026-06-22

Numio checks your formulas as you build and computes them defensively at runtime, so a reader never sees a raw spreadsheet error. This article explains the verified state and how invalid or unusual formulas behave.

The verified state

When you click Save on a formula in the expression editor, Numio tries to parse and evaluate it against a sample scope:

  • If it parses, the formula is marked verified. Verified formulas are shown in their group's color in the data tables.
  • If it can't parse, it isn't verified. The expression input turns red, and the formula stays unverified — but it is still kept.

A formula that has content but isn't verified shows a red row highlight in the formula table, so unfinished or broken formulas are easy to spot at a glance. An empty formula simply shows in gray rather than red.

Invalid formulas still save

Numio doesn't block you from saving a formula it couldn't verify. The text you entered is preserved so you can come back and fix it — verification is a signal, not a gate. Just remember that an unverified formula may not produce the result you expect when the calculator runs.

How errors are handled at runtime

The engine that computes results for your readers is built to never throw a visible error. Instead of #REF!, #DIV/0!, or #NAME?, it falls back to safe values:

  • Unknown functions silently return 0. If a formula calls a function Numio doesn't support, that call evaluates to 0 rather than failing. (See the functions reference for the supported list.)
  • Division by zero returns 0 instead of infinity or an error.
  • Empty and non-numeric cells count as 0 in arithmetic.
  • A cell that can't resolve to a number gives 0 — for example a result block pointed at a blank or broken cell shows 0.

Circular references

If a formula ends up referring back to itself — directly or through a chain of other cells — Numio detects the cycle and returns 0 for the looping reference rather than hanging or crashing. The rest of the workbook still computes normally.

Because these fallbacks are silent, a result of 0 can sometimes mean "the formula couldn't compute" rather than "the answer is zero." If a result is unexpectedly 0, check that:

  • every function you used is on the supported list,
  • referenced cells actually contain values,
  • and the formula doesn't reference itself.

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