# Prove whether this language is (partially) decidable [duplicate]

I'm currently working on a few turing machine exercises and I can't understand how I can prove whether the below is at least partially decidable:

$\{M \mid L(M) = \{x \mid |x| = 10\}\;\}$ where $|x|$ is the length of word $x$

Can anyone explain to me what the above statement actually means and an idea of how to go about it please?

## marked as duplicate by Raphael♦Nov 4 '17 at 20:27

• This statement means the set of TM indexes (natural numbers under some fixed encoding) where each TM accepts a language containing all strings of length $10$. – fade2black Nov 3 '17 at 19:31
• Another way to explain it, "$\{x \mid |x| = 10\}$ is the (finite) set of strings of length $10$. $L(M)$ represents the language accepted by $M$. $A = \{ M \mid ...\mbox{ someproperty }... \}$ represents the set of Turing machines that satisfy "someproperty". Your question is: given a Turing machine $M$ does there exist an algorithm that is able to halt if $M$ accepts exactly the strings of length $10$ and rejects all the strings longer or shorter than $10$? If yes then $A$ is partially decidable. – Vor Nov 4 '17 at 20:08