Note 4 - Stock-based Compensation (Details Textual)	9 Months Ended
Jan. 26, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	5,800
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price \| $ / shares	$ 13.40
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	322,645
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance \| $ / shares	$ 10.64
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,814,413

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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