/**
 * Runtime registry mapping function names to their {@link FormulaFunction}
 * implementations. It is the single extension point for adding functions —
 * built-ins are registered at construction, and developers register custom
 * functions through the same API with no engine changes.
 *
 * @packageDocumentation
 */
import type { FormulaFunction } from './formula-function';
/**
 * A name → {@link FormulaFunction} lookup table.
 *
 * Lookup is case-insensitive by default (Excel semantics): names are stored
 * upper-cased. When constructed with `caseSensitive = true`, names are stored
 * verbatim and matched exactly.
 *
 * Registration is last-wins, so a custom function may deliberately override a
 * built-in of the same name.
 */
export declare class FunctionRegistry {
    private readonly caseSensitive;
    private readonly functions;
    /**
     * @param caseSensitive - When `true`, function names are matched exactly;
     *                        otherwise they are normalized to upper-case.
     */
    constructor(caseSensitive?: boolean);
    /** Normalizes a name to its lookup key per the case-sensitivity setting. */
    private key;
    /**
     * Registers (or overrides) a function.
     *
     * @param fn - The function implementation. Its {@link FormulaFunction.name}
     *             is used as the key.
     */
    register(fn: FormulaFunction): void;
    /**
     * Registers many functions in one call.
     *
     * @param fns - The function implementations to register.
     */
    registerAll(fns: Iterable<FormulaFunction>): void;
    /**
     * Removes a function by name.
     *
     * @param name - The function name (case-normalized per settings).
     * @returns `true` if a function was removed.
     */
    unregister(name: string): boolean;
    /**
     * Looks up a function by name.
     *
     * @param name - The function name as written in a formula.
     * @returns The implementation, or `undefined` if not registered.
     */
    get(name: string): FormulaFunction | undefined;
    /**
     * @param name - The function name as written in a formula.
     * @returns `true` if a function with this name is registered.
     */
    has(name: string): boolean;
    /** @returns The number of registered functions. */
    get size(): number;
    /** @returns All registered function names (normalized). */
    names(): string[];
}
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