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Kotlin Programming: The Big Nerd Ranch Guide, First Edition by David Greenhalgh, Josh Skeen

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Modifying Map Values

To complete the transaction, the price of the item should be deducted from the patron’s purse. The patronGold map associates gold balance values with a given patron’s name as a key. You will modify the gold balance value for a patron to record the patron’s new balance once the purchase is completed.

Your performPurchase and displayBalance functions are tied to Madrigal’s purse and get into details of gold and silver pieces that are not needed here. Delete them and the playerGold and playerSilver variables, which are only used in those functions. Then define a new performPurchase function to handle a patron purchase. (You will define a new function to display patron balances soon.)

To update the value after the ...

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