Questions tagged [turing-completeness]

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54
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6answers
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Are there minimum criteria for a programming language being Turing complete?

Does there exist a set of programming language constructs in a programming language in order for it to be considered Turing Complete? From what I can tell from wikipedia, the language needs to ...
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9answers
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Why are some programming languages Turing complete but lack some abilities of other languages?

I came across an odd problem when writing an interpreter that (should) hooks to external programs/functions: Functions in 'C' and 'C++' can't hook variadic functions, e.g. I can't make a function that ...
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9answers
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Is C actually Turing-complete?

I was trying to explain to someone that C is Turing-complete, and realized that I don't actually know if it is, indeed, technically Turing-complete. (C as in the abstract semantics, not as in an ...
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5answers
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What does being Turing complete mean?

I see that most definitions of what it is to be Turing-complete are tautological to a degree. For example if you Google "what does being Turing complete mean", you get: A computer is Turing ...
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5answers
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Can regular languages be Turing complete?

I was reading about Iota and Jot and found this section confusing: Unlike Iota, where the syntactic tree for a string can branch either on the left or on the right, Jot syntax is uniformly left-...
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7answers
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Are all turing complete languages interchangeable

Note, while I know how to program, I'm quite a beginner at CS theory. According to this answer Turing completeness is an abstract concept of computability. If a language is Turing complete, then ...
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5answers
6k views

Why are functional languages Turing complete?

Perhaps my limited understanding of the subject is incorrect, but this is what I understand so far: Functional programming is based off of Lambda Calculus, formulated by Alonzo Church. Imperative ...
21
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1answer
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Does a do-while loop suffice for Turing-completeness?

I know that, in imperative programming languages, a while-do loop is sufficient as a control flow construct to make the language Turing-complete (as far as control flow goes - of course we also need ...
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2answers
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Universality of the Toffoli gate

Regarding the quantum Toffoli gate: is it classicaly universal, and if so, why? is it quantumly universal, and why?
17
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2answers
6k views

How is the rule 110 Turing complete?

I've read the wikipedia page for rule 110 in cellular automata, and I more or less know how they work (a set of rules decides where to draw the next 1 or 0). I've just read they're Turing complete, ...
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4answers
2k views

What is required for universal analogue computation?

What operations need to be performed in order to do any arbitrary analogue computation? Would addition, subtraction, multiplication and division be sufficient? Also, does anyone know exactly what ...
15
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2answers
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What makes PROLOG Turing-complete?

I know that it can be proven PROLOG is Turing-complete by constructing a program that simulates a Turing machine like this: ...
14
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2answers
3k views

Connection between NAND gates and Turing completeness

I know that NAND gates can be used to create circuits that implement every truth table, and modern computers are built up of NAND gates. What is the theoretical link between NAND gates and Turing ...
14
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1answer
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Is There a Complete Problem for the Class of Turing Decidable Problems?

Languages such as $\text{HALT}_{TM}$ are $\textsf{RE-complete}$ under many-one reductions. It is trivial to see that $\text{co-RE}$ has complete problems, too. S. Schmitz [1] considers some classes ...
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2answers
591 views

Do Higher Order Functions provide more power to Functional Programming?

I've asked a similar question on cstheory.SE. According to this answer on Stackoverflow there is an algorithm that on a non-lazy pure functional programming language has an $\Omega(n \log n)$ ...
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3answers
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Can every self-modifying algorithm be modelled by a non-selfmodifying algorithm?

If we have any arbitrary computer program that can modify its instructions, is it possible to simulate that program with a program that cannot modify its instructions? Edit: I am new to ...
12
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2answers
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How many pairs of brackets are sufficient to make Brainfuck Turing complete?

Brainfuck is a Turing complete programming language that uses only 8 symbols (6 if you ignore I/O). The two most notable ones that push it to Turing completeness are ...
12
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1answer
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Is any language that can express its own compiler Turing-complete?

A comment over on tex.SE made me wonder. The statement is essentially: If I can write a compiler for language X in language X, then X is Turing-complete. In computability and formal languages ...
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2answers
3k views

Clear, complete, proof that a language is Turing Compete?

I have seen web sites that purport to "prove" that HTML5+CSS is Turing Complete. I have seen web sites that purport to "prove" that SQL is Turing Complete. I have seen a bunch of web sites that ...
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1answer
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How can a universal Turing machine simulate “bigger” ones?

I'm trying to find the answers of two questions about the Universal Turing machine. How can the Universal Turing machine simulate a Turing machine if the one that is being simulated has a bigger ...
10
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1answer
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Is there a dual concept to “Turing Complete” in logic?

Two computing models can be shown to be co complete if each can encode a universal simulator for the other. Two logics can be shown to be co complete if an encoding of the rules of inferences (and ...
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2answers
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Are Boolean functions Turing complete

A Boolean function is a function $f:\{0,1\}^n\rightarrow\{0,1\}$. The boolean basis $(\vee,\wedge)$ is known to be Turing complete as it allows any sequence $s\in\{0,1\}$ to be flipped or to be left ...
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2answers
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Is a stack machine with a forward read iterator Turing complete?

It is well known that a machine with a single stack as only unlimited storage is not Turing complete, if it can only read from the top of the stack. I want a machine which is (slightly) more powerful ...
7
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1answer
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How close are common programming languages to not being Turing complete?

The term "Turing completeness" has been discussed in several of the Computer Science classes that I've taken. However, I've never gotten an intuitive feel for what Turing completeness actually ...
7
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0answers
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Automata that is Turing complete if you add a nondeterminism

Pushdown automata have an interesting property: non-deterministic ones belong to a different computational class than deterministic ones. This is in contrast to finite state and turing machines, for ...
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0answers
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Make a tag system simulate a finite automaton?

Tag systems are Turing-complete. I was wondering if there is any easy way to create tag systems that simulate finite automata. So create tag systems that recognize languages, e.g. by having at the end ...
6
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2answers
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Is there a way to test “Turing completeness”?

I asked my algorithms teacher today the very same question that is stated in the title, but he seemed a bit unsure, either on the question or on the concept, so I thought I'd try here too. Is there a ...
6
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4answers
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Can we write algorithms without conditional statements?

Regarding turing completeness, i read that for a language/machine to be turing complete it is required that it has some sort of conditional. Consider the factorial problem, we would typically define ...
6
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4answers
484 views

Is a device with restrictive execution policies Turing-complete?

There are devices that do not allow users to load any application they want on it, only run a limited class of applications approved by the device vendor. Take an iPhone as an example where new ...
6
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2answers
788 views

Looping and branching with Algorithmic Differentiation

Algorithmic (aka Automatic) Differentiation is a wonderful technique for numerical computation of derivatives. I understand how it relates to the fact that we know how to deal with every elementary ...
6
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1answer
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Is model theory useful for computer scientists

It is often stated in the CS folklore that Turing was inspired by Gödel's incompleteness theorem, more specifically the diagonalization proof and the isomorphism between axiomatically generated ...
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1answer
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How is PowerPoint Turing complete?

From my understanding, Turing complete means that the program or machine can complete any computation that a Turing machine can complete, which to me means any computation. So how can something like ...
6
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4answers
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Is the halting problem always decidable for non-universal programs?

For every non-universal computable program $P$ that takes input of type $D$ does there exist some total computable function $g$ that takes an input $I$ of type $D$ and decides successfully whether $P$ ...
6
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0answers
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Unbounded-time programs in lambda calculus?

The Turing machine model has been extended to “infinitary turing machines”, which are Turing machines that can perform a countably and uncountably infinite amount of computations in finite time. Is ...
6
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0answers
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On the Turing Completeness of First Order Logic

It is well known that in Descriptive Complexity Theory FO is equivalent to AC0. However, this accepts a couple of a theory and a string <T,s> iff the ...
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3answers
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Is there an algorithm for converting Turing machines into equivalent Lambda expressions?

We know that Turing machines and Lambda Calculus are equivalent in power. And There are proofs for that, I'm sure. But is there an algorithm, a systematic way for us to convert a Turing machine into ...
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4answers
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Are Finite Automata Turing Complete?

Something is Turing Complete if it can be used to simulate any Turing Machine. So, can a Finite Automaton simulate a Turing Machine? On the question Can regular languages be Turing complete? they ...
5
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5answers
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Is there any example of automatas (or similar) systems that emerge complex internal structures on its own?

Automatas are turing-complete grid-based systems with progression rules on which we can encode arbitrarily complex structures. For example, this is a "glider gun" on Conway's Game of Life: Due to ...
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4answers
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Do we need recursion in programming language to solve any problem?

My question is simple: If we want to be able to solve every problem, that we can solve using recursions, do we need programming language to allow us use recursions? Assuming we are allowed to use: ...
5
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2answers
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Does a Universal Turing Machine have more computational power than a non-universal one?

I'm a bit confused about these concepts. As far as I understand, something is Turing complete when it can simulate a Turing machine. And there is this thing called a Universal Turing machine which is ...
5
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1answer
859 views

Is something more than Turing complete Turing complete?

In complexity theory, we do not call a decision problem that is not in NP "NP-complete". But in computability, do we call a machine model "Turing complete" if it can compute functions which Turing ...
5
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1answer
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Simplest Turing-complete ruleset for Markov algorithm

Is there an example of a particular ruleset for a Markov algorithm that is Turing-complete? If so, what is the simplest example of such a ruleset?
5
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1answer
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Can a language be Turing Complete if its only provision for unlimited code/memory is through recursion?

We've developed an esoteric language. In this language, a program contains a static amount of code, and a static amount of storage space. However, parts of the program can recurse, so the interpreter ...
5
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1answer
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How rule 110 would be proven to be universal if the tag system did not exist?

I was reading about Cellular Automata and I read in this question that Matthew Cook proved that rule 110 is universal, and that his proof relied upon showing how rule 110 can simulate a tag system. ...
5
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1answer
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Is a LBA with stack more powerful than a LBA without?

Even so a linear bounded automata (LBA) is strictly more powerful than a pushdown automata (PDA), adding a stack to a LBA might make it more powerful. A LBA with stack should not be Turing complete, ...
5
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2answers
277 views

Is a language with only a stack of fixed-size integers Turing-complete?

I encountered the brainfuck programming language which I know is turing complete. However I then decided to create a high level language that gets compiled to brainfuck code. There is only one data ...
5
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1answer
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Confused between turing-completeness and universal approximation - are they related?

I am trying to de-knot a point of confusion in my mind regarding "turing-completeness" and the "universal approximation theorem". The context here is deep neural nets: So, consider two types of ...
5
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0answers
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Why does Turing Tumble need gear bits to be turing complete?

I understand intuitively that gear bits in the massively successful Turing Tumble game (funded by kickstarter) are necessary for Turing completeness*. I had a fantasy about building a computer with ...
5
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0answers
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Computational power of Actor Model

In the question below, let TM be Turing machine, NTM be nondeterministic Turing machine and PTM be probabilistic Turing machine. In his paper "Actor Model of Computation: Scalable Robust Information ...
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2answers
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Non Recursively Enumerable Languages

Can someone give me an example of Non Recursively Enumerable language... i.e. A language which no Turing machine can accept ? What makes a language non recursively enumerable ?