Variable keeps getting error that it may not be defined in my user-built function.

53 次查看（过去 30 天）
Sean
Sean 2024-10-24，1:01
编辑： dpb 2024-10-24，15:57
function computerColumn = computerPicksColumn(currentTokens)
% determines where the computer will drop a black token
% INPUTS:
% currentTokens: 6 by 7 matrix of integers that are 1 (yellow)
% 2 (red token) and 3 (black token)
% RETURNS:
% computerColumn: an integer between 1 and 7 that represents a column
% that is not full, i.e. a token could be dropped in it
% Initialize the column choice
computerColumn = randi(7); % Randomly chooses a column from 1 to 7
tokenValue = 3; % black tokens have a value of 3
% Check if the chosen column is valid
while true
% Check if the column is full
% Find the lowest available row in the chosen column
for row = 6:-1:1
if currentTokens(row, computerColumn) == 1
currentTokens(row, computerColumn) = tokenValue; % Place the token
return; % Exit the function after placing the token
end
end
end
end
this is the code, right above in the if statement the second line (currentTokens(r,c) = tokenValue) keeps giving an error message that variable assigned to variable might be unused.

请先登录，再回答此问题。

回答（1 个）

dpb
dpb 2024-10-24，14:41
编辑：dpb 2024-10-24，15:57
That is because it isn't used (referenced again after set).
When the function returns, the local array of that name will be lost(*); the return value is defined to be ComputerColumn and MATLAB is (by operation if not strictly by implementation) "call by value" so the array in the argument list is not updated in the caller's workspace.
You need to change the return variables to match; if the intent is to modify currentTokens in the caller, then you need to return it as well...
function [computerColumn, currentTokens] = computerPicksColumn(currentTokens)
(*) See <Base and Function Workspaces> on the different workspaces functions operate under.

类别

在 Help Center 和 File Exchange 中查找有关 Web Services 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by