Formatting results

Evaluation and presentation are separate. The engine produces a value; turning it into text is a second step you control.

import { formatValue } from "solve-engine/format";

formatValue(value); // "= 3000.00 m"

The leading = marker suits an editor result gutter. Strip it when rendering elsewhere.

Settings

formatValue takes an optional second argument, a full FormattingSettings object grouped by value type: decimal places for floats, units and percentages, padding for hex, and the locale used for the decimal separator.

It is a complete object, not a patch. Passing a few loose keys will not merge with the defaults, it will leave the rest undefined and throw. Spread DEFAULT_FORMATTING_SETTINGS and override the group you care about:

import { formatValue, DEFAULT_FORMATTING_SETTINGS } from "solve-engine/format";

formatValue(value, {
  ...DEFAULT_FORMATTING_SETTINGS,
  unitOfMeasurementResult: { decimalPlaces: 0 },
}); // "= 3000 m"

The groups are floatResult, numberResult, hexResult, unitOfMeasurementResult and percentageResult. Their fields are listed in the API reference.

Formatting yourself

Nothing obliges you to use the built-in formatter. A value exposes its type, its raw payload and its unit, which is enough to render however your product needs, and is often less code than fighting the settings for an unusual layout.

import { ValueType } from "solve-engine/vm";

function render(value): string {
  switch (value.type) {
    case ValueType.Uom:
      return `${value.toNumber().toLocaleString()} ${value.unit}`;
    case ValueType.Percentage:
      return `${value.toNumber()}%`;
    case ValueType.Pending:
      return "…";
    case ValueType.Error:
      return "";
    default:
      return String(value.toNumber());
  }
}

Handle Pending and Error explicitly. They are ordinary value types rather than exceptions, so a formatter that assumes every value is a finished number will render “NaN” the moment a currency line is still loading.