manybody/tools.hpp File Reference

Some mathematical and other tools. More...

#include <string>
#include <sstream>
#include <cmath>
#include <vector>

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Functions
std::string	format (double x, int prec=16)
	Simple function to format a double with a given precision. Useful if we don't want to mess with, e.g., cout's settings and produce predictable double-output.
void	print_copyright (std::ostream &os)
	Print copyright notice.
std::string	move_to (int N)
	Move to position (using ANSI escape seq.).
double	lnfact (int n)
	Compute ln(n!).
double	fact (int n)
	Compute n!.
double	lnbinom (int n, int m)
	Compute log of factorial, ln(n!/m!/(n-m)!).
double	binom (int n, int m)
	Compute "n ober m" = n!/(m!(n-m)!).
template<typename T>
std::string	yesno (const T &x)
	Return string "yes" if true, "no" if false.
template<typename T>
int	m1pow (const T &i)
	Compute pow(-1,i). Used a lot!
template<typename T>
T	sqr (const T &x)
	Compute square of number; used a lot!
template<class T>
size_t	count_bits (const T &x)
	Count bits in a word. See http://graphics.stanford.edu/~seander/bithacks.html.
template<typename T>
std::string	to_binary (const T &a, const size_t &n=0)
	Compute a binary string version of number.
template<class Vector>
bool	general_inc (Vector &alpha, int min, int max, size_t digit=0)
	Simple recursive function to step through multi-indices.
bool	more_general_inc (std::vector< int > &alpha, const std::vector< int > &min, const std::vector< int > &max, int digit=0)
	Simple recursive function to step through multi-indices. More general version of general_inc(). Here, the max and min values are different for each index in the multi-index.

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Detailed Description

Some mathematical and other tools.

Author:

Simen Kvaal

Date:

6-13-08

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Function Documentation

double binom	(	int	n,
		int	m
	)			[inline]

Compute "n ober m" = n!/(m!(n-m)!).

Parameters:

	n	a number
	m	a number

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double fact

(

int

n

)

[inline]

Compute n!.

Parameters:

n

number to take factorial of

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std::string format	(	double	x,
		int	prec = 16
	)			[inline]

Simple function to format a double with a given precision. Useful if we don't want to mess with, e.g., cout's settings and produce predictable double-output.

Parameters:

	x	number to write
	prec	precision

template<class Vector>

bool general_inc	(	Vector &	alpha,
		int	min,
		int	max,
		size_t	digit = 0
	)			[inline]

Simple recursive function to step through multi-indices.

The template parameter Vector must implement Vector::size() and Vector::operator[]().

Parameters:

	alpha	Multi-index
	min	Minimum value of each index
	max	Maximum value + 1 of each index
	digit	Which digit to increase. User should not use this; used for recursion.

Returns:

true if alpha = (max-1,max-1,....,max-1) upon entry, such that it wraps around to (min,min,...min); false otherwise.

double lnbinom	(	int	n,
		int	m
	)			[inline]

Compute log of factorial, ln(n!/m!/(n-m)!).

Parameters:

	n	a number
	m	a number

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double lnfact

(

int

n

)

[inline]

Compute ln(n!).

Parameters:

n

number to take factorial of

bool more_general_inc	(	std::vector< int > &	alpha,
		const std::vector< int > &	min,
		const std::vector< int > &	max,
		int	digit = 0
	)			[inline]

Simple recursive function to step through multi-indices. More general version of general_inc(). Here, the max and min values are different for each index in the multi-index.

The template parameter Vector must implement Vector::size() and Vector::operator[]().

Parameters:

	alpha	Multi-index
	min	Minimum value of each index
	max	Maximum value + 1 of each index
	digit	Which digit to increase. User should not use this; used for recursion.

Returns:

true if alpha = (max[0]-1,max[1]-1,....,max[n]-1) upon entry, such that it wraps around to (min[0],min[1]...,min[n]); false otherwise.

std::string move_to

(

int

N

)

[inline]

Move to position (using ANSI escape seq.).

Parameters:

N

position on line, should be >=0.

template<typename T>

std::string to_binary	(	const T &	a,
		const size_t &	n = 0
	)

Compute a binary string version of number.

Parameters:

	a	Number to convert
	n	Number of bits to use; n = 0 (default) means all bits.

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