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feat: add the C src files
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef STDLIB_STATS_BASE_DISTS_CHI_VARIANCE_H
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#define STDLIB_STATS_BASE_DISTS_CHI_VARIANCE_H
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/*
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* If C++, prevent name mangling so that the compiler emits a binary file having undecorated names, thus mirroring the behavior of a C compiler.
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*/
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* Returns the variance of a chi distribution.
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*
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* @param k degrees of freedom (must be non-negative)
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* @return variance
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*/
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double stdlib_base_dists_chi_variance( const double k );
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#ifdef __cplusplus
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}
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#endif
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#endif // !STDLIB_STATS_BASE_DISTS_CHI_VARIANCE_H
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#/
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# @license Apache-2.0
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#
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# Copyright (c) 2025 The Stdlib Authors.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#/
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# VARIABLES #
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ifndef VERBOSE
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QUIET := @
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else
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QUIET :=
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endif
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# Determine the OS ([1][1], [2][2]).
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#
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# [1]: https://en.wikipedia.org/wiki/Uname#Examples
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# [2]: http://stackoverflow.com/a/27776822/2225624
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OS ?= $(shell uname)
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ifneq (, $(findstring MINGW,$(OS)))
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OS := WINNT
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else
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ifneq (, $(findstring MSYS,$(OS)))
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OS := WINNT
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else
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ifneq (, $(findstring CYGWIN,$(OS)))
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OS := WINNT
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else
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ifneq (, $(findstring Windows_NT,$(OS)))
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OS := WINNT
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endif
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endif
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endif
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endif
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# RULES #
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#/
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# Removes generated files for building an add-on.
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#
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# @example
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# make clean-addon
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#/
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clean-addon:
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$(QUIET) -rm -f *.o *.node
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.PHONY: clean-addon
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#/
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# Removes generated files.
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#
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# @example
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# make clean
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#/
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clean: clean-addon
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.PHONY: clean
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "stdlib/math/base/napi/unary.h"
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#include "stdlib/stats/base/dists/chi/variance.h"
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// cppcheck-suppress shadowFunction
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STDLIB_MATH_BASE_NAPI_MODULE_D_D( stdlib_base_dists_chi_variance )
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "stdlib/math/base/assert/is_nan.h"
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#include "stdlib/stats/base/dists/chi/mean.h"
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/**
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* Returns the variance of a chi distribution.
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*
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* @param k degrees of freedom (must be non-negative)
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* @return variance, or NaN if input is invalid
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*
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* @example
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* double v = stdlib_base_dists_chi_variance( 9.0 );
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* // returns ~0.485
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*
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* @example
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* double v = stdlib_base_dists_chi_variance( 1.0 );
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* // returns ~0.363
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*
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* @example
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* double v = stdlib_base_dists_chi_variance( -0.2 );
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* // returns NaN
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*
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* @example
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* double v = stdlib_base_dists_chi_variance( NAN );
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* // returns NaN
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*/
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double stdlib_base_dists_chi_variance( const double k ) {
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if ( stdlib_base_is_nan( k ) || k < 0.0 ) {
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return 0.0 / 0.0; // NaN
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}
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double mu = stdlib_base_dists_chi_mean( k );
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return k - ( mu * mu );
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}

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