# Questions tagged [fixed-point]

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### Quines that output functions of code and input

​​A Quine is a (non-empty) program that takes no inputs and returns its own source code as the output. For a function f: strings * 'a -> 'b, define an f-Quine as a program P that takes an input x ...
71 views

### Self referential hash function possible?

Is there a hashing function $f$ that for each input $x$ if $f(x) = y$, then $f(x \, || \, y) = y$? In other words, if we concatenate its output with the input, the result will not change. Furthermore, ...
418 views

### How is the input to a BROUWER algorithm done

The Brouwer fixpoint theorem states that any continuous mapping $f$, from a convex, compact set to itself will contain a fixpoint. The Brouwer algorithm finds these (approximate) fixpoints. But how is ...
210 views

### Bisimulation and the Knaster–Tarski theorem: What does the least fixed point mean?

Given a suitable lattice and a monotonic function $F$, we can compute the bisimilarity of a labeled transition system (its greatest bisimulation) by computing the greatest fixed point of $F$ using ...
59 views

### What are the fixed-points of the Y combinator?

Since the Y combinator itself is a function (albeit a higher-order one), I was wondering what the fixed-points of Y itself are.
1 vote
49 views

### Is there a term for the inverse of a fixed-point operator?

When working with recursion it is often useful to find the least or greatest fixed points of a morphism, often using a fixed-point combinator. When working with recursion schemes, the inverse ...
1 vote
33 views

### How do we know that $F^{n + 1}(\overrightarrow{\emptyset}) = F(F^n(\overrightarrow{\emptyset}))$?

I am currently studying the textbook Principles of Program Analysis by Flemming Nielson, Hanne R. Nielson, and Chris Hankin. Chapter 1.3 Data Flow Analysis says the following: The least solution. The ...
285 views

### How to prove that the Church encoding, forall r. (F r -> r) -> r, gives an initial algebra of the functor F?

The well-known Church encoding of natural numbers can be generalized to use an arbitrary (covariant) functor F. The result is the type, call it ...
1 vote
166 views

### Find the fixed point of a recursive functional?

A functional is a function which takes another function as a parameter. The fixed point of a function is an input such that F(x) = x Given an example functional, <...
114 views

### Termination of Z combinator with call-by-value

I am trying to build my own λ-calculus interpreter. So far it supports both call-by-value and normal order. I now want to try recursion via fixed points. The $Y$ combinator works with normal order, ...
1 vote
101 views

### Fixed Points of Factorial Function

(This is taken from the book Semantics with Applications) I'm trying to determine the fixed points for the following block: ...
35 views

### Trying to determine Fixed Points

I'm basically trying to solve 4.2 (Taken from Semantics with Applications) As I see it, the functional F will be defined like so: ...
844 views

### Fixed point of hash

Are hashing algorithms constructed to guarantee that no fixed point exists? My assumption is not, because I don’t see what utility that would have. (Please correct me if I’m wrong.) As such, purely ...
378 views

### Logical characterization of P versus NP problem (and references for least fixed point logic)

Wikipedia says the following (and more) about the logical characterization of the P versus NP problem here: Thus, the question "is P a proper subset of NP" can be reformulated as "is existential ...
878 views

### Why Does the Fixed Point Theorem Apply to Quines?

A quine is a program that outputs its own source code without taking in any input. An example would be this (taken from here) ...
1 vote
3k views

### How does conversion from fixed-point to floating-point happen?

I came across to the code that convert 32-bit signed fixed-point number (16.16) to a float and it looks like (pseudocode) floating = fixed / 65536.0 Could you ...
1 vote
38 views

### Hebbian rule doesn't get to a fixpoint

I'm trying to implement an Hopfield Network for pictures of 32x32 bits either 1 or -1; I have these 3 pictures and I transform each of them in a vector of 1024 elements. Then I take the 3 vectors and ...
1 vote
157 views

### Is Datalog negation and the built-in predicate $\neq$ similar?

I was reading "Principles of Database & Knowledge-Base Systems, Vol. 1" by Jeffrey D. Ullman. There is a chapter about Datalog negation and as I was seeing the problems of negation I kept thinking ...
1 vote
474 views

### Neural Networks: Simulate the working of Dynamic Fixed Point representation of the weights on hardware

I am looking to implement a neural network on hardware using Verilog. I have completed and tested with floating point representation and a 20 bit fixed point representation. I want to further reduce ...
2k views

### What is a fixpoint?

Could someone please explain me, what is a fix point? I caught the minimum explanation about fix point from the website: After infinitely many iterations we should get to a fix point where ...
141 views

### Why doesn't this quine-less language contradict Kleene's recursion theorem?

Kleene's recursion theorem implies that every Turing complete programming language that satisfies certain properties have quines. This website claims that this is incorrect, and that there is a Turing ...
746 views

### Decimal to Fixed Point Conversion

I am having trouble to get the intuition behind the following approach: We take the fraction point (say: .642) and continuously multiply by 2, taking whatever ends up right of the point as our next ...
Assume a CPO $Q,\leq$ and a Scott-continuous function $f : Q \rightarrow Q$. As it is known, the chain $\bot \leq f(\bot) \leq \ldots \leq f^n(\bot)$ (where $f^n$ denotes the function $n-1$-times ...