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