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udf_stdnorm_density.cc
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udf_stdnorm_density.cc
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/*
returns the value of the density function of
the standard normal distribution for a given point
input parameters:
point (int or real)
number of decimals in result (int, optional)
output:
value of the density function of the standard normal distribution (real)
registering the function:
CREATE FUNCTION stdnorm_density RETURNS REAL SONAME 'udf_stdnorm_density.so';
getting rid of the function:
DROP FUNCTION stdnorm_density;
*/
#ifdef STANDARD
#include <stdio.h>
#include <string.h>
#ifdef __WIN__
typedef unsigned __int64 ulonglong;
typedef __int64 longlong;
#else
typedef unsigned long long ulonglong;
typedef long long longlong;
#endif /*__WIN__*/
#else
#include <my_global.h>
#include <my_sys.h>
#endif
#include <mysql.h>
#include <m_ctype.h>
#include <m_string.h>
#ifdef HAVE_DLOPEN
extern "C"
{
my_bool stdnorm_density_init(UDF_INIT *, UDF_ARGS *args, char *message);
double stdnorm_density(UDF_INIT *initid, UDF_ARGS *args, char *is_null,char *error);
}
my_bool stdnorm_density_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
if (args->arg_count != 1 && args->arg_count != 2)
{
strcpy(message,"stdnorm_density() must have one or two arguments");
return 1;
}
if (args->arg_type[0] != INT_RESULT && args->arg_type[0]!=REAL_RESULT)
{
strcpy(message,"stdnorm_density() must have an integer or a real as parameter 1");
return 1;
}
initid->decimals = 2;
if (args->arg_count==2 && args->arg_type[1]!=INT_RESULT)
{
strcpy(message,"stdnorm_density() must have an integer as parameter 2");
return 1;
}
if (args->arg_count==2 && (*((ulong*)args->args[1])<=16))
{
initid->decimals=*((ulong*)args->args[1]);
}
initid->maybe_null = 0;
initid->max_length = 20;
return 0;
}
double stdnorm_density(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error)
{
double x;
if (args->arg_type[0]==INT_RESULT)
{
x=(double) *((longlong*)args->args[0]);
} else if (args->arg_type[0]==REAL_RESULT)
{
x=(double) *((double*) args->args[0]);
}
return pow(2.71828182845904523536,-0.5*x*x)/2.506628274631000241612355;
}
#endif /* HAVE_DLOPEN */