Function asSmallInteger

src/compute-engine/boxed-expression/numerics.ts:139–167

(
  expr: number | Expression | undefined
)

 * Unlike `toInteger()` this functions fails if the expression is not an
 * integer. `toInteger()` will round the value to the nearest integer.
 */
export function asSmallInteger(
  expr: number | Expression | undefined
): number | null {
  if (expr === undefined || expr === null) return null;
  if (typeof expr === 'number') {
    if (
      Number.isInteger(expr) &&
      expr >= -SMALL_INTEGER &&
      expr <= SMALL_INTEGER
    )
      return expr;
    return null;
  }
  if (!isNumber(expr)) return null;
  const num = expr.numericValue;

  if (typeof num === 'number') {
    if (Number.isInteger(num) && num >= -SMALL_INTEGER && num <= SMALL_INTEGER)
      return num;
    return null;
  }

  if (num.im !== 0) return null;

  const n = num.re;
  if (Number.isInteger(n) && n >= -SMALL_INTEGER && n <= SMALL_INTEGER)
    return Number(n);
  return null;
}

/**