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@mapbox/mapbox-gl-style-spec

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a specification for mapbox gl styles

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import {array, ValueType, NumberType} from '../types'; import RuntimeError from '../runtime_error'; import type {Expression, SerializedExpression} from '../expression'; import type ParsingContext from '../parsing_context'; import type EvaluationContext from '../evaluation_context'; import type {Type, ArrayType} from '../types'; import type {Value} from '../values'; class At implements Expression { type: Type; index: Expression; input: Expression; constructor(type: Type, index: Expression, input: Expression) { this.type = type; this.index = index; this.input = input; } static parse(args: ReadonlyArray<unknown>, context: ParsingContext): At | null | void { if (args.length !== 3) return context.error(`Expected 2 arguments, but found ${args.length - 1} instead.`); const index = context.parse(args[1], 1, NumberType); const input = context.parse(args[2], 2, array(context.expectedType || ValueType)); if (!index || !input) return null; const t = input.type as ArrayType; return new At(t.itemType, index, input); } evaluate(ctx: EvaluationContext): Value { const index = (this.index.evaluate(ctx) as number); const array = (this.input.evaluate(ctx) as Array<Value>); if (index < 0) { throw new RuntimeError(`Array index out of bounds: ${index} < 0.`); } if (index >= array.length) { throw new RuntimeError(`Array index out of bounds: ${index} > ${array.length - 1}.`); } if (index !== Math.floor(index)) { throw new RuntimeError(`Array index must be an integer, but found ${index} instead. Use at-interpolated to retrieve interpolated result with a fractional index.`); } return array[index]; } eachChild(fn: (_: Expression) => void) { fn(this.index); fn(this.input); } outputDefined(): boolean { return false; } serialize(): SerializedExpression { return ["at", this.index.serialize(), this.input.serialize()]; } } export default At;