### Setup WASM Build Environment

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/wasm/README.md

Installs the wasm32-unknown-unknown target and the wasm-bindgen CLI for building Rust WASM projects.

```bash
rustup target add wasm32-unknown-unknown --toolchain nightly
wasm-bindgen --version
```

--------------------------------

### Install Rust

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/wasm/README.md

Installs Rust using the official installation script. Ensure you have a stable internet connection.

```bash
curl https://sh.rustup.rs -sSf | sh
```

--------------------------------

### Install hpx-cli using pip

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Install the hpx-cli tool and its executable for Python users via pip. This is a quick way to get started if you are working within a Python environment.

```bash
pip install -U hpx-cli
hpx --help
```

--------------------------------

### Start Local HTTP Server (Python 3)

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/wasm/README.md

Starts a simple HTTP server using Python 3 for serving local files. Useful for testing web assets.

```bash
python -m http.server
```

--------------------------------

### Start Local HTTP Server (Python 2)

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/wasm/README.md

Starts a simple HTTP server using Python 2 for serving local files. Useful for testing web assets.

```bash
python -m SimpleHTTPServer
```

--------------------------------

### Build and Install HEALPix PSQL Extension

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Builds the release version of the HEALPix extension using native CPU features and installs it. This is a prerequisite before creating the extension in the database.

```bash
RUSTFLAGS='-C target-cpu=native' cargo build --release
make
make install
```

--------------------------------

### Install hpx-cli from Source using Cargo

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Build and install the hpx-cli tool from the cloned source code using Cargo, Rust's package manager. Note that compilation may take a significant amount of time due to heavy monomorphization.

```bash
cargo install --path crates/cli
```

--------------------------------

### Find PostgreSQL Library Directory

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Utility command to locate the directory where PostgreSQL extensions are installed. Useful for troubleshooting installation issues.

```bash
pg_config --pkglibdir
```

--------------------------------

### Compile for 32-bit Target on 64-bit Linux

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/README.md

To target 32-bit on a 64-bit Linux system, first install the target using rustup, then install the necessary multilib support for GCC, and finally build with the specified target and RUSTFLAGS.

```bash
rustup target install i686-unknown-linux-gnu
sudo apt-get install gcc-multilib
RUSTFLAGS=' - C target-cpu=native' cargo build - - target=i686-unknown-linux-gnu - - release
```

--------------------------------

### Install cdshealpix Python Package

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/README.md

Installs the cdshealpix Python package using pip. This command is used to set up the Python interface for cdshealpix.

```bash
pip install -U cdshealpix
```

--------------------------------

### Update Rust Compiler

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Ensure you have the latest Rust compiler installed, which may be necessary for building the hpx-cli from source. This command updates your existing Rust toolchain.

```bash
rustup update
```

--------------------------------

### Run HEALPix PSQL Extension Regression Tests

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Executes the regression tests for the HEALPix PostgreSQL extension to verify its installation and functionality. May require specifying a PostgreSQL user with creation permissions.

```bash
make installcheck
```

```bash
PGUSER=postgres make installcheck
```

--------------------------------

### Approximate Cone Overlap MOC

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/README.md

Generates a HEALPix MOC representing the cells overlapped by a given cone, using an approximate method. Requires importing `get` and `Layer` from `cdshealpix::nested`.

```rust
use cdshealpix::nested::{get, Layer};

let depth = 6_u8;
let nested_d6 = get(depth);

let lon = 13.158329_f64.to_radians();
let lat = - 72.80028_f64.to_radians();
let radius = 5.64323_f64.to_radians();

let moc = nested_d6.cone_overlap_approx(lon, lat, radius);
for cell in moc.into_iter() {
println ! ("cell: {:?}", cell);
}
```

--------------------------------

### Get HEALPix Cell Vertices

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/README.md

Retrieves the spherical coordinates of the four vertices for a given HEALPix cell at a specified depth. Requires importing `get_or_create` and `Layer` from `cdshealpix::nested`.

```rust
use cdshealpix::nested::{get_or_create, Layer};

let depth = 12_u8;
let cell_number= 10_u64;

let nested_d12 = get_or_create(depth);

let [
(lon_south, lat_south),
(lon_east,  lat_east),
(lon_north, lat_north),
(lon_west,  lat_west)
] = nested_d12.vertices(cell_number);
```

--------------------------------

### Compute HEALPix Cell Number

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/README.md

Calculates the HEALPix cell number for a given spherical position at a specific depth. Requires importing `nside`, `get`, and `Layer` from `cdshealpix`.

```rust
use cdshealpix::nside;
use cdshealpix::nested::{get, Layer};


let depth = 12_u8;
let lon = 12.5_f64.to_radians();
let lat = 89.99999_f64.to_radians();

let nested_d12 = get(depth);
let nside = nside(depth) as u64;
let expected_cell_number = nside * nside - 1;

assert_eq!(expected_cell_number, nested_d12.hash(lon, lat));
```

--------------------------------

### Initialize HEALPix WebAssembly Module

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/wasm/demo.html

Initializes the WebAssembly module and sets up an event listener for the compute button. This code should be run when the page loads.

```javascript
delete WebAssembly.instantiateStreaming;

function init() {
  hpx = wasm_bindgen;
  $('#compute').click(function() {
    $('#hpxhash').val(hpx.lonlatToNested($('#depth').val(), $('#lon').val(), $('#lat').val()));
  });
}

wasm_bindgen('./cdshealpix_bg.wasm')
  .then(init)
  .catch(console.error);
```

--------------------------------

### HEALPix CLI Main Help

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Displays the main help message for the HEALPix CLI tool, listing available commands and global options.

```bash
> hpx --help
Command-line tool to play with HEALPix

Usage: hpx <COMMAND>

Commands:
  proj    Computes the projected coordinates (x, y) ∊ ([0..8[, [-2..2]) of input equatorial coordinates
  unproj  Computes the equatorial coordinates of Healpix projected coordinates (x, y) ∊ ([0..8[, [-2..2])
  nested  Operations in the HEALPix NESTED scheme
  sort    Sorts a CSV file by order 29 HEALPix NESTED indices, uses external sort to support huge files
  hcidx   Create an index on an HEALPix NESTED sorted CSV file to then quickly retrieve rows in a given HEALPix cell
  qhcidx  Query an HEALPix sorted and indexed CSV file (see the 'hcidx' command)
  map     Create and manipulate HEALPix count and density maps
  mom     Create and manipulate HEALPix count and density maps
  cov     Compute the list of NESTED Healpix cells in a given sky region (see also moc-cli)
  help    Print this message or the help of the given subcommand(s)

Options:
  -h, --help     Print help
  -V, --version  Print version

```

--------------------------------

### HEALPix WebAssembly Initialization and Usage

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/wasm/test.html

Initializes the HEALPix WebAssembly module and demonstrates calling various HEALPix functions from JavaScript. This snippet shows how to use the 'hpx' alias for wasm_bindgen and logs the output of different HEALPix operations to the browser console.

```javascript
delete WebAssembly.instantiateStreaming;

function run() {
  // use 'hpx', an alias nicer than 'wasm_bindgen'
  hpx = wasm_bindgen;
  console.log("You can call methods (coordinate are given and returned in degrees):")
  console.log(" hpx.getOrderMax()")
  console.log(" hpx.lonlatToNested(order, ra, dec)")
  console.log(" hpx.multiLonlatToNested(order, [ra1, dec1, ra2, dec2, ..., raN, decN])")
  console.log(" hpx.nestedCenter(order, cellNumber)")
  console.log(" hpx.vertices(order, cellNumber)")
  console.log(" hpx.nestedNeighbours(order, cellNumber)")
  console.log(" hpx.nestedQueryCone(order, cone_ra, cone_dec, cone_radius)")
  console.log(" hpx.nestedQueryConeBMOC(order, cone_ra, cone_dec, cone_radius)")
  console.log(" hpx.nestedQueryPolygon(order, [ra1, dec1, ra2, dec2, ..., raN, decN])")
  console.log(" hpx.nestedQueryPolygonBMOC(order, [ra1, dec1, ra2, dec2, ..., raN, decN])")
  console.log("From a BMOC, you can get its number of cells `bmoc.getSize()` and access each cell `bmoc.getCell(i)`")
  console.log("From a Cell, you can access directly its `order`, `icell` and `idfull` attributes")
  console.log("")
  console.log("Unrelated to HELPix: multi-polygone query")
  console.log(" map = hpx.PolygonMap.new()")
  console.log(" map.addPolygon(int_ID, [ra1, dec1, ra2, dec2, ..., raN, decN]);")
  console.log(" map.addPolygon(int_ID, [ra1, dec1, ra2, dec2, ..., raN, decN]);")
  console.log(" map.polygonContaining(ra, dec);")
  console.log(" map.rmPolygon(int_ID);")
}

wasm_bindgen('./cdshealpix_bg.wasm')
  .then(run)
  .catch(console.error);

Look at your web browser console!
```

--------------------------------

### Compile with Native CPU Optimizations

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/README.md

To achieve best performance on your hardware, compile using RUSTFLAGS='-C target-cpu=native'. This enables BMI2 instructions PDEP and PEXT for bit interleaving if supported by your processor.

```bash
RUSTFLAGS='-C target-cpu=native' cargo build --release
```

--------------------------------

### Visualize Density MOM Map as PNG

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Converts a HEALPix density MOM FITS file into a PNG image for visualization. This process is faster than visualizing the raw density map.

```bash
time hpx mom view --silent gaia_edr3_dist.dens.mom.fits gaia_edr3_dist.dens.mom.png allsky 400

real	0m0,494s
user	0m0,478s
sys	0m0,013s
```

--------------------------------

### Initialize KaTeX Rendering for Math Expressions

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/katex.html

This script renders KaTeX math expressions found in elements with the class 'language-math' in display mode. It also processes inline math expressions marked with '$'.

```javascript
use strict";
document.addEventListener("DOMContentLoaded", function () {
    var maths = document.getElementsByClassName("language-math");
    for (var i=0; i<maths.length; i++) {
        var el = maths[i];
        katex.render(el.innerText, el, {displayMode: true});
    }
    var codes = document.getElementsByTagName("code");
    for (i=0; i<codes.length; i++) {
        el = codes[i];
        if (el.classList.contains("language-math")) continue;
        if (el.classList.contains("language-inline-math")) {
            katex.render(el.innerText, el);
            continue;
        }
        var parent = el.parentNode;
        if (parent.nodeName.toLowerCase() === "pre") continue;
        // TODO: Can this be done with DOM manipulation rather than string manipulation?
        // https://stackoverflow.com/q/48438067/3019990
        var inlineMath = "$" + el.outerHTML + "$";
        if (parent.innerHTML.indexOf(inlineMath) !== -1) {
            el.classList.add("language-inline-math");
            parent.innerHTML = parent.innerHTML.replace("$" + el.outerHTML + "$", el.outerHTML);
            i--;
        }
    }
});
```

--------------------------------

### HEALPix Nested Scheme Help

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Shows the help message for the 'nested' subcommand, detailing operations within the HEALPix NESTED scheme.

```bash
> hpx nested --help
Operations in the HEALPix NESTED scheme

Usage: hpx nested <COMMAND>

Commands:
  table       Prints the table of Healpix layers properties (depth, nside, ncells, ...)
  bestdepth   For a cone of given radius, returns the largest depth at which the cone covers max 9 cells
  hash        Get the Healpix hash value (aka ipix or cell number) of given equatorial position(s)
  bilinear    Get the bilinear interpolation parameters, 4x(hash, weight), of given equatorial position(s)
  center      Get the longitude and latitude (in degrees) of the center of the cell of given hash value
  vertices    Get the longitude and latitude (in degrees) of the 4 vertices (S, W, N, E) of the cell of given hash value
  neighbours  Get the hash value (aka ipix or cell number) of the neighbours of the cell of given hash value (S, SE, E, SW, NE, W, NW, N)
  touniq      Transform regular hash values (aka ipix or cell numbers) into the UNIQ representation
  toring      Transform regular hash values (aka ipix or cell numbers) from the NESTED to the RING scheme
  help        Print this message or the help of the given subcommand(s)

Options:
  -h, --help  Print help


```

--------------------------------

### HEALPix Coverage Command Help

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Displays help for the 'cov' command, used to compute HEALPix cell coverage for various sky regions.

```bash
> hpx cov --help
Compute the list of NESTED Healpix cells in a given sky region (see also moc-cli)

Usage: hpx cov [OPTIONS] <DEPTH> <COMMAND>

Commands:
  cone      Cone coverage
  ellipse   Elliptical cone coverage
  ring      Ring coverage
  zone      Zone coverage
  box       Box coverage
  polygon   Polygon coverage
  stcs      STC-S region coverage
  stcsfile  STC-S region provided in a file coverage
  convert   From reading a regular FITS encoded BMOC
  help      Print this message or the help of the given subcommand(s)

Arguments:
  <DEPTH>
          Maximum depth (aka order) of the Healpix cells in the coverage

Options:
  -t, --out-type <OUTPUT_TYPE>
          Output type
          
          [default: csv]

          Possible values:
          - csv:      CSV serialization
          - fits:     FITS serialization
          - bintable: FITS BINTABLE serialization

  -o, --output-file <FILE>
          Write in the given output file instead of stdout (mandatory for FITS)

  -h, --help
          Print help (see a summary with '-h')


```

--------------------------------

### Visualize Density MOM Map Zoomed Region

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Generates a PNG visualization of a specific region of a density MOM map. Provides a compressed and noise-reduced view of localized data.

```bash
> time hpx mom view --silent gaia_edr3_dist.dens.mom.fits gaia_edr3_dist.dens.mom.lmc.png custom -l 280.4652 -b -32.8884 sin 400 400 --x-bounds [-0.15..0.15] --y-bounds [-0.15..0.15]

real	0m0,237s
user	0m0,227s
sys	0m0,010s
```

--------------------------------

### Visualize Density Map as PNG

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Converts a HEALPix density map FITS file into a PNG image for visualization. Supports custom projections and dimensions.

```bash
> time hpx map view --silent gaia_edr3_dist.dens.fits gaia_edr3_dist.dens.png allsky 400

real	0m20,361s
user	0m19,246s
sys	0m0,492s
```

--------------------------------

### Benchmark Native CPU Optimizations

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/README.md

You can test the performance impact of native CPU optimizations by running benchmarks. If the result of 'ZOrderCurve/BMI' is slower than 'ZOrderCurve/LUPT', it is recommended to compile without 'native' support.

```bash
RUSTFLAGS='-C target-cpu=native' cargo bench
```

--------------------------------

### Create HEALPix Extension in PostgreSQL

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

This SQL command registers the HEALPix extension within your PostgreSQL database, making its functions available for use. It only needs to be run once.

```sql
CREATE EXTENSION pg_cds_healpix;
```

--------------------------------

### Compute Density Map from CSV

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Builds a HEALPix density map from a large CSV file. Use this for initial density estimation. Supports parallel processing and chunking for large files.

```bash
> time hpx map dens 11 gaia_edr3_dist.dens.fits csv -d , -l 2 -b 3 --header --chunk-size 100000000 --parallel 32 gaia_edr3_dist.csv

real	15m27,858s
user	27m20,545s
sys	34m42,810s
```

--------------------------------

### Clone CDS HEALPix Rust Project

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Obtain the source code for the CDS HEALPix Rust library, which is required if you plan to build the hpx-cli from source. This command clones the official repository.

```bash
git clone https://github.com/cds-astro/cds-healpix-rust
```

--------------------------------

### Compute Density Map (Optimized)

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

An optimized method for computing density maps by piping pre-processed CSV data. This approach is faster for single-threaded operations.

```bash
> time cut -d , -f 2,3 gaia_edr3_dist.csv | tail -n +2 \
  | hpx map dens 11 gaia_edr3_dist.dens.fits list -d ,

real	8m25,812s
user	11m7,242s
sys	3m40,669s
```

--------------------------------

### Compute BMOC for a Sky Cone

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Computes a Binary Occupancy Cube (BMOC) for a specified cone on the sky. This is used to represent regions of interest efficiently.

```bash
time hpx cov 9 --out-type fits --output-file cone.bmoc.fits cone 080.8942 -69.7561 0.2

real	0m0,006s
user	0m0,001s
sys	0m0,005s
```

--------------------------------

### Visualize Density Map Zoomed Region

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Generates a PNG visualization of a specific region of a density map. Useful for detailed inspection of smaller areas.

```bash
> time hpx map view --silent gaia_edr3_dist.dens.fits gaia_edr3_dist.dens.lmc.png custom -l 280.4652 -b -32.8884 sin 400 400 --x-bounds [-0.15..0.15] --y-bounds [-0.15..0.15]

real	0m7,507s
user	0m7,277s
sys	0m0,229s
```

--------------------------------

### Index Sorted CSV File to HEALPix FITS

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Indexes a pre-sorted CSV file into a HEALPix FITS format. This is useful for creating compact and queryable HEALPix indices.

```bash
time hpx hcidx --header -d , --depth 9 -o gaia_edr3_dist.sorted.hci.fits -l 2 -b 3 gaia_edr3_dist.sorted.csv

real	6m39,257s
user	4m51,979s
sys	1m30,032s
```

--------------------------------

### Visualize and Center HEALPix Cells from BMOC

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Converts a BMOC to a list of HEALPix cells and computes their centers. This helps in visualizing the coverage of the BMOC.

```bash
time hpx cov 9 convert cone.bmoc.fits | tail -n +2 | hpx nested center 9 csv -d , -f 2 --header --paste --paste-header "center_lon,center_lat"
order,ipix,is_fully_covered_flag,center_lon,center_lat
9,2118189,0,080.7110091743119,-69.9794867201383
9,2118191,0,080.3424657534247,-69.8866968891410
9,2118194,0,081.1238532110092,-69.9794867201383
9,2118195,0,081.1643835616438,-69.8866968891410
9,2118196,0,081.5753424657534,-69.7938937311056
9,2118197,0,081.6136363636364,-69.7938937311056
9,2118198,0,081.2045454545455,-69.7938937311056
9,2118199,0,081.2443438914027,-69.7010771793946
9,2118200,0,080.7534246575343,-69.8866968891410
9,2118201,1,080.7954545454545,-69.7938937311056
9,2118202,0,080.3863636363636,-69.7938937311056
9,2118203,0,080.4298642533936,-69.7010771793946
9,2118204,1,080.8371040723982,-69.7010771793946
9,2118205,0,080.8783783783784,-69.6082471672874
9,2118206,0,080.4729729729730,-69.6082471672874
9,2118207,0,080.5156950672646,-69.5154036279795
9,2118240,0,081.6515837104072,-69.7010771793946
9,2118242,0,081.2837837837838,-69.6082471672874
9,2118248,0,080.9192825112108,-69.5154036279795

real	0m0,008s
user	0m0,005s
sys	0m0,013s
```

--------------------------------

### Convert Density Map to Density MOM

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Converts a density map into a density MOM (multi-resolution map) using a chi-square criterion. This significantly compresses the data and removes noise.

```bash
> time hpx map convert gaia_edr3_dist.dens.fits gaia_edr3_dist.dens.mom.fits dens2chi2mom

real	0m0,978s
user	0m0,661s
sys	0m0,317s
```

--------------------------------

### Query HEALPix Index with BMOC

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Queries a HEALPix index file using a BMOC to retrieve and count sources within the specified regions. This is a fast operation for large datasets.

```bash
time hpx qhcidx gaia_edr3_dist.sorted.hci.fits bmoc cone.bmoc.fits | wc -l
240021

real	0m0,207s (0m0.034s with a hot cache)
user	0m0,000s
sys	0m0,076s
```

--------------------------------

### hpx_nside

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Computes the Nside for a given HEALPix depth. The depth must be between 0 and 29.

```APIDOC
## hpx_nside(INTEGER)->INTEGER

### Description
Computes the Nside for a given HEALPix depth. The depth must be an integer within the range [0, 29].

### Parameters
#### Path Parameters
- **depth** (INTEGER) - Required - The HEALPix depth.

### Response
#### Success Response (200)
- **nside** (INTEGER) - The computed Nside value.

### Response Example
```json
{
  "nside": 16
}
```
```

--------------------------------

### Sort Large CSV File by HEALPix Order

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/cli/README.md

Sorts a large CSV file based on HEALPix indices. Use this to prepare data for efficient HEALPix indexing.

```bash
time hpx sort --header -d , -o gaia_edr3_dist.sorted.csv -l 2 -b 3 gaia_edr3_dist.csv

real  89m5,997s
user  184m9.269s
sys 23m21,342s
```

--------------------------------

### hpx_hash

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Computes the hash/index of a HEALPix cell for a given position and depth. Depth must be [0,29] and latitude [-90,90].

```APIDOC
## hpx_hash(INTEGER, DOUBLE PRECISION, DOUBLE PRECISION)->BIGINT

### Description
Computes the hash/index of the HEALPix cell including the given position at the given depth. The depth must be within [0,29] and the latitude within [-90,90].

### Parameters
#### Path Parameters
- **depth** (INTEGER) - Required - The HEALPix depth.
- **latitude** (DOUBLE PRECISION) - Required - The latitude of the position.
- **longitude** (DOUBLE PRECISION) - Required - The longitude of the position.

### Response
#### Success Response (200)
- **hash** (BIGINT) - The computed HEALPix cell hash/index.

### Response Example
```json
{
  "hash": 19456
}
```
```

--------------------------------

### hpx_center

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Computes the center coordinates (longitude, latitude) of a specified HEALPix cell. Depth must be [0,29] and hash within [0, 12*Nside^2[.

```APIDOC
## hpx_center(INTEGER, BIGINT)->DOUBLE PRECISION[]

### Description
Computes the center of the specified HEALPix cell. The depth must be within [0,29] and the hash within [0, 12*Nside^2[.

### Parameters
#### Path Parameters
- **depth** (INTEGER) - Required - The HEALPix depth.
- **hash** (BIGINT) - Required - The hash/index of the HEALPix cell.

### Response
#### Success Response (200)
- **center** (DOUBLE PRECISION[]) - An array containing the longitude and latitude of the cell's center.

### Response Example
```json
{
  "center": [69.609375, 34.2288663278126]
}
```
```

--------------------------------

### Compute HEALPix Hash

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Computes the HEALPix cell hash (index) for a given depth and spherical coordinates (longitude, latitude). Valid depths are [0, 29] and latitudes are [-90, 90].

```sql
psql=# SELECT hpx_hash(6, 0.0, 0.0);
 hpx_hash
----------
    19456
(1 row)
```

--------------------------------

### Compute HEALPix Nside

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Calculates the Nside value for a given HEALPix depth. Ensure the depth is within the valid range [0, 29].

```sql
psql=# SELECT hpx_nside(4);

hpx_nside
-----------
        16
(1 row)
```

--------------------------------

### Compute HEALPix Cell Center

Source: https://github.com/cds-astro/cds-healpix-rust/blob/master/crates/libpsql/README.md

Calculates the center coordinates (longitude, latitude) of a specified HEALPix cell identified by its depth and hash. Ensure depth is within [0, 29] and hash is within [0, 12*Nside^2[.

```sql
psql=# SELECT hpx_center(6, 1234);
          hpx_center        
------------------------------
 {69.609375,34.2288663278126}
(1 row)
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.