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Undefined values: Difference between revisions
→{{header|Mathematica}}
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=={{header|Mathematica}}==
Mathematica is a symbolic mathematical software. Variables without given values are treated as symbols.
<lang Mathematica>ConditionalExpression[a, False]▼
<lang Mathematica>a
->Undefined▼
-> a
a + a
-> 2 a
ValueQ[a]
-> False
a = 5
-> 5
ValueQ[a]
-> True</lang>
Mathematica also has a build-in symbol "Undefined", representing a quantity with no defined value.
▲<lang Mathematica>ConditionalExpression[a, False]
->Undefined</lang>
Mathematical expressions containing Undefined evaluate to Undefined:
<lang Mathematica>Sin[Undefined]
-> Undefined </lang>
Of course you can assign Undefined to be the value of a variable. Here "Undefined" is itself a value.
<lang Mathematica>a = Undefined
▲-> Undefined
a
-> Undefined
ValueQ[a]
-> True</lang>
=={{header|MATLAB}} / {{header|Octave}}==
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