Why is exist(variable,'var') not seeing a variable?

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Bogdan Dzyubak
Bogdan Dzyubak 2018-9-24
回答： Steven Lord 2018-9-24
I have a function to which a variable is passed. The variable exists:
'signedOrNot = signed'
When I call 'exist signedOrNot var' it is found:
ans = 1
But when I use exist(signedOrNot,'var'), as I would in an if statement, it is not:
ans = 0
Any thoughts?

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采纳的回答

Fangjun Jiang
Fangjun Jiang 2018-9-24
exist('signedOrNot','var')

更多回答（1 个）

Steven Lord
Steven Lord 2018-9-24
This line of code tests whether the variable with the name signedOrNot exists in the workspace.
exist('signedOrNot', 'var')
This line of code tests whether the variable whose name is stored in the variable signedOrNot exists in the workspace.
exist(signedOrNot, 'var')
Compare:
% if a variable by this name exists, choose a different name
signedOrNot = 'thisVariableShouldNotExist';
passingName = exist('signedOrNot', 'var') % true, signedOrNot exists
passingContentsOfVariable = exist(signedOrNot, 'var') % false, thisVariableShouldNotExist doesn't
with:
x = 42;
signedOrNot = 'x';
passingName = exist('signedOrNot', 'var') % true, signedOrNot exists
passingContentsOfVariable = exist(signedOrNot, 'var') % true, x exists

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