import { Expr } from '../gpu/contract';

/** One item's field accessors at a loop index (the packed vec4 lane, decoded per kind). */
export interface ListItemAt {
    /** `position` fields: vec2 in the stored (x, 1−y) convention — what a position uniform holds. */
    position: (field: string) => Expr;
    /** `color` fields: linear rgba vec4. */
    color: (field: string) => Expr;
    /** `number` / `boolean` fields: f32 (booleans are ±1). */
    number: (field: string) => Expr;
}
export interface ListRef {
    /** The live item count (f32 uniform). */
    count: Expr;
    /** Field accessors for item `i` (an Expr indexing the lane arrays). */
    at: (i: Expr) => ListItemAt;
}
/** Bind a list prop's uniforms. */
export declare function listOf(params: {
    uniforms: Record<string, Expr>;
}, prop: string): ListRef;
/**
 * Sum a per-item expression over a list: `var acc = zero; for (i < count) { acc += body(i) }`.
 * `zero` sets the accumulator type (`'f32'` or `'vec3f'`). Statement machinery — see the module
 * header for the hoisting rule.
 */
export declare function accumulate(list: ListRef, body: (i: Expr) => Expr, opts?: {
    zero?: 'f32' | 'vec3f';
    deps?: Expr[];
    hint?: string;
}): Expr;
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