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feat: add C implementation for math/base/special/factorialln
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PR-URL: stdlib-js#2731 
Ref: stdlib-js#649 

Reviewed-by: Philipp Burckhardt <[email protected]>
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gunjjoshi committed Aug 21, 2024
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88 changes: 88 additions & 0 deletions lib/node_modules/@stdlib/math/base/special/factorialln/README.md
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<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/factorialln.h"
```

#### stdlib_base_factorialln( x )

Evaluates the natural logarithm of the [factorial function][factorial-function]. For input values other than negative integers, the function returns `ln( x! ) = ln( Γ(x+1) )`, where `Γ` is the [Gamma][gamma-function] function. For negative integers, the function returns `NaN`.

```c
double out = stdlib_base_factorialln( 3.0 );
// returns ~1.792

out = stdlib_base_factorialln( -1.5 );
// returns ~1.266
```

The function accepts the following arguments:

- **x**: `[in] double` input value.

```c
double stdlib_base_factorialln( const double n );
```
</section>
<!-- /.usage -->
<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
<section class="notes">
</section>
<!-- /.notes -->
<!-- C API usage examples. -->
<section class="examples">
### Examples
```c
#include "stdlib/math/base/special/factorialln.h"
#include <stdio.h>
int main( void ) {
const double x[] = { 2.0, 3.0, 5.0, 8.0 };
double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_factorialln( x[ i ] );
printf( "factorialln(%lf) = %lf\n", x[ i ], y );
}
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">
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/**
* @license Apache-2.0
*
* Copyright (c) 2024 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';

// MODULES //

var resolve = require( 'path' ).resolve;
var bench = require( '@stdlib/bench' );
var randu = require( '@stdlib/random/base/randu' );
var floor = require( '@stdlib/math/base/special/floor' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var tryRequire = require( '@stdlib/utils/try-require' );
var pkg = require( './../package.json' ).name;


// VARIABLES //

var factorialln = tryRequire( resolve( __dirname, './../lib/native.js' ) );
var opts = {
'skip': ( factorialln instanceof Error )
};


// MAIN //

bench( pkg+'::native,integers', opts, function benchmark( b ) {
var x;
var y;
var i;

b.tic();
for ( i = 0; i < b.iterations; i++ ) {
x = floor( randu() * 171.0 ) + 1.0;
y = factorialln( x );
if ( isnan( y ) ) {
b.fail( 'should not return NaN' );
}
}
b.toc();
if ( isnan( y ) ) {
b.fail( 'should not return NaN' );
}
b.pass( 'benchmark finished' );
b.end();
});

bench( pkg+'::native,decimals', opts, function benchmark( b ) {
var x;
var y;
var i;

b.tic();
for ( i = 0; i < b.iterations; i++ ) {
x = ( randu() * 171.0 ) + 1.0;
y = factorialln( x );
if ( isnan( y ) ) {
b.fail( 'should not return NaN' );
}
}
b.toc();
if ( isnan( y ) ) {
b.fail( 'should not return NaN' );
}
b.pass( 'benchmark finished' );
b.end();
});
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#/
# @license Apache-2.0
#
# Copyright (c) 2024 The Stdlib Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#/

# VARIABLES #

ifndef VERBOSE
QUIET := @
else
QUIET :=
endif

# Determine the OS ([1][1], [2][2]).
#
# [1]: https://en.wikipedia.org/wiki/Uname#Examples
# [2]: http://stackoverflow.com/a/27776822/2225624
OS ?= $(shell uname)
ifneq (, $(findstring MINGW,$(OS)))
OS := WINNT
else
ifneq (, $(findstring MSYS,$(OS)))
OS := WINNT
else
ifneq (, $(findstring CYGWIN,$(OS)))
OS := WINNT
else
ifneq (, $(findstring Windows_NT,$(OS)))
OS := WINNT
endif
endif
endif
endif

# Define the program used for compiling C source files:
ifdef C_COMPILER
CC := $(C_COMPILER)
else
CC := gcc
endif

# Define the command-line options when compiling C files:
CFLAGS ?= \
-std=c99 \
-O3 \
-Wall \
-pedantic

# Determine whether to generate position independent code ([1][1], [2][2]).
#
# [1]: https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#Code-Gen-Options
# [2]: http://stackoverflow.com/questions/5311515/gcc-fpic-option
ifeq ($(OS), WINNT)
fPIC ?=
else
fPIC ?= -fPIC
endif

# List of includes (e.g., `-I /foo/bar -I /beep/boop/include`):
INCLUDE ?=

# List of source files:
SOURCE_FILES ?=

# List of libraries (e.g., `-lopenblas -lpthread`):
LIBRARIES ?=

# List of library paths (e.g., `-L /foo/bar -L /beep/boop`):
LIBPATH ?=

# List of C targets:
c_targets := benchmark.out


# RULES #

#/
# Compiles source files.
#
# @param {string} [C_COMPILER] - C compiler (e.g., `gcc`)
# @param {string} [CFLAGS] - C compiler options
# @param {(string|void)} [fPIC] - compiler flag determining whether to generate position independent code (e.g., `-fPIC`)
# @param {string} [INCLUDE] - list of includes (e.g., `-I /foo/bar -I /beep/boop/include`)
# @param {string} [SOURCE_FILES] - list of source files
# @param {string} [LIBPATH] - list of library paths (e.g., `-L /foo/bar -L /beep/boop`)
# @param {string} [LIBRARIES] - list of libraries (e.g., `-lopenblas -lpthread`)
#
# @example
# make
#
# @example
# make all
#/
all: $(c_targets)

.PHONY: all

#/
# Compiles C source files.
#
# @private
# @param {string} CC - C compiler (e.g., `gcc`)
# @param {string} CFLAGS - C compiler options
# @param {(string|void)} fPIC - compiler flag determining whether to generate position independent code (e.g., `-fPIC`)
# @param {string} INCLUDE - list of includes (e.g., `-I /foo/bar`)
# @param {string} SOURCE_FILES - list of source files
# @param {string} LIBPATH - list of library paths (e.g., `-L /foo/bar`)
# @param {string} LIBRARIES - list of libraries (e.g., `-lopenblas`)
#/
$(c_targets): %.out: %.c
$(QUIET) $(CC) $(CFLAGS) $(fPIC) $(INCLUDE) -o $@ $(SOURCE_FILES) $< $(LIBPATH) -lm $(LIBRARIES)

#/
# Runs compiled benchmarks.
#
# @example
# make run
#/
run: $(c_targets)
$(QUIET) ./$<

.PHONY: run

#/
# Removes generated files.
#
# @example
# make clean
#/
clean:
$(QUIET) -rm -f *.o *.out

.PHONY: clean
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