#define IN_LIBEXSLT
#include "libexslt/libexslt.h"

#include <libxml/tree.h>
#include <libxml/xpath.h>
#include <libxml/xpathInternals.h>

#include <libxslt/xsltutils.h>
#include <libxslt/xsltInternals.h>
#include <libxslt/extensions.h>

#ifdef HAVE_MATH_H
#include <math.h>
#endif

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif

#include "exslt.h"

/**
 * exsltMathMin:
 * @ns:  a node-set
 *
 * Implements the EXSLT - Math min() function:
 *    number math:min (node-set)
 *
 * Returns the minimum value of the nodes passed as the argument, or
 *         xmlXPathNAN if @ns is NULL or empty or if one of the nodes
 *         turns into NaN.
 */
static double
exsltMathMin (xmlNodeSetPtr ns) {
    double ret, cur;
    int i;

    if ((ns == NULL) || (ns->nodeNr == 0))
	return(xmlXPathNAN);
    ret = xmlXPathCastNodeToNumber(ns->nodeTab[0]);
    if (xmlXPathIsNaN(ret))
	return(xmlXPathNAN);
    for (i = 1; i < ns->nodeNr; i++) {
	cur = xmlXPathCastNodeToNumber(ns->nodeTab[i]);
	if (xmlXPathIsNaN(cur))
	    return(xmlXPathNAN);
	if (cur < ret)
	    ret = cur;
    }
    return(ret);
}

/**
 * exsltMathMinFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathMin for use by the XPath processor.
 */
static void
exsltMathMinFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    xmlNodeSetPtr ns;
    double ret;
    void *user = NULL;

    if (nargs != 1) {
	xsltGenericError(xsltGenericErrorContext,
			 "math:min: invalid number of arguments\n");
	ctxt->error = XPATH_INVALID_ARITY;
	return;
    }
    /* We need to delay the freeing of value->user */
    if ((ctxt->value != NULL) && (ctxt->value->boolval != 0)) {
        user = ctxt->value->user;
	ctxt->value->boolval = 0;
	ctxt->value->user = NULL;
    }
    ns = xmlXPathPopNodeSet(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathMin(ns);

    xmlXPathFreeNodeSet(ns);
    if (user != NULL)
        xmlFreeNodeList((xmlNodePtr)user);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathMax:
 * @ns:  a node-set
 *
 * Implements the EXSLT - Math max() function:
 *    number math:max (node-set)
 *
 * Returns the maximum value of the nodes passed as arguments, or
 *         xmlXPathNAN if @ns is NULL or empty or if one of the nodes
 *         turns into NaN.
 */
static double
exsltMathMax (xmlNodeSetPtr ns) {
    double ret, cur;
    int i;

    if ((ns == NULL) || (ns->nodeNr == 0))
	return(xmlXPathNAN);
    ret = xmlXPathCastNodeToNumber(ns->nodeTab[0]);
    if (xmlXPathIsNaN(ret))
	return(xmlXPathNAN);
    for (i = 1; i < ns->nodeNr; i++) {
	cur = xmlXPathCastNodeToNumber(ns->nodeTab[i]);
	if (xmlXPathIsNaN(cur))
	    return(xmlXPathNAN);
	if (cur > ret)
	    ret = cur;
    }
    return(ret);
}

/**
 * exsltMathMaxFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathMax for use by the XPath processor.
 */
static void
exsltMathMaxFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    xmlNodeSetPtr ns;
    double ret;
    void *user = NULL;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }

    /* We need to delay the freeing of value->user */
    if ((ctxt->value != NULL) && (ctxt->value->boolval != 0)) {
	user = ctxt->value->user;
	ctxt->value->boolval = 0;
	ctxt->value->user = 0;
    }
    ns = xmlXPathPopNodeSet(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathMax(ns);

    xmlXPathFreeNodeSet(ns);

    if (user != NULL)
        xmlFreeNodeList((xmlNodePtr)user);
    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathHighest:
 * @ns:  a node-set
 *
 * Implements the EXSLT - Math highest() function:
 *    node-set math:highest (node-set)
 *
 * Returns the nodes in the node-set whose value is the maximum value
 *         for the node-set.
 */
static xmlNodeSetPtr
exsltMathHighest (xmlNodeSetPtr ns) {
    xmlNodeSetPtr ret = xmlXPathNodeSetCreate(NULL);
    double max, cur;
    int i;

    if ((ns == NULL) || (ns->nodeNr == 0))
	return(ret);

    max = xmlXPathCastNodeToNumber(ns->nodeTab[0]);
    if (xmlXPathIsNaN(max))
	return(ret);
    else
	xmlXPathNodeSetAddUnique(ret, ns->nodeTab[0]);

    for (i = 1; i < ns->nodeNr; i++) {
	cur = xmlXPathCastNodeToNumber(ns->nodeTab[i]);
	if (xmlXPathIsNaN(cur)) {
	    xmlXPathEmptyNodeSet(ret);
	    return(ret);
	}
	if (cur < max)
	    continue;
	if (cur > max) {
	    max = cur;
	    xmlXPathEmptyNodeSet(ret);
	    xmlXPathNodeSetAddUnique(ret, ns->nodeTab[i]);
	    continue;
	}
	xmlXPathNodeSetAddUnique(ret, ns->nodeTab[i]);
    }
    return(ret);
}

/**
 * exsltMathHighestFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathHighest for use by the XPath processor
 */
static void
exsltMathHighestFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    xmlNodeSetPtr ns, ret;
    void *user = NULL;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }

    /* We need to delay the freeing of value->user */
    if ((ctxt->value != NULL) && ctxt->value->boolval != 0) {
        user = ctxt->value->user;
	ctxt->value->boolval = 0;
	ctxt->value->user = NULL;
    }
    ns = xmlXPathPopNodeSet(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathHighest(ns);

    xmlXPathFreeNodeSet(ns);
    if (user != NULL)
        xmlFreeNodeList((xmlNodePtr)user);

    xmlXPathReturnNodeSet(ctxt, ret);
}

/**
 * exsltMathLowest:
 * @ns:  a node-set
 *
 * Implements the EXSLT - Math lowest() function
 *    node-set math:lowest (node-set)
 *
 * Returns the nodes in the node-set whose value is the minimum value
 *         for the node-set.
 */
static xmlNodeSetPtr
exsltMathLowest (xmlNodeSetPtr ns) {
    xmlNodeSetPtr ret = xmlXPathNodeSetCreate(NULL);
    double min, cur;
    int i;

    if ((ns == NULL) || (ns->nodeNr == 0))
	return(ret);

    min = xmlXPathCastNodeToNumber(ns->nodeTab[0]);
    if (xmlXPathIsNaN(min))
	return(ret);
    else
	xmlXPathNodeSetAddUnique(ret, ns->nodeTab[0]);

    for (i = 1; i < ns->nodeNr; i++) {
	cur = xmlXPathCastNodeToNumber(ns->nodeTab[i]);
	if (xmlXPathIsNaN(cur)) {
	    xmlXPathEmptyNodeSet(ret);
	    return(ret);
	}
        if (cur > min)
	    continue;
	if (cur < min) {
	    min = cur;
	    xmlXPathEmptyNodeSet(ret);
	    xmlXPathNodeSetAddUnique(ret, ns->nodeTab[i]);
            continue;
	}
	xmlXPathNodeSetAddUnique(ret, ns->nodeTab[i]);
    }
    return(ret);
}

/**
 * exsltMathLowestFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathLowest for use by the XPath processor
 */
static void
exsltMathLowestFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    xmlNodeSetPtr ns, ret;
    void *user = NULL;


    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }

    /* We need to delay the freeing of value->user */
    if ((ctxt->value != NULL) && (ctxt->value->boolval != 0)) {
        user = ctxt->value->user;
	ctxt->value->boolval = 0;
	ctxt->value->user = NULL;
    }
    ns = xmlXPathPopNodeSet(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathLowest(ns);

    xmlXPathFreeNodeSet(ns);
    if (user != NULL)
        xmlFreeNodeList((xmlNodePtr)user);

    xmlXPathReturnNodeSet(ctxt, ret);
}

/* math other functions */

/* constant values */
#define EXSLT_PI        (const xmlChar *) \
			"3.1415926535897932384626433832795028841971693993751"
#define EXSLT_E         (const xmlChar *) \
			"2.71828182845904523536028747135266249775724709369996"
#define EXSLT_SQRRT2    (const xmlChar *) \
			"1.41421356237309504880168872420969807856967187537694"
#define EXSLT_LN2       (const xmlChar *) \
			"0.69314718055994530941723212145817656807550013436025"
#define EXSLT_LN10      (const xmlChar *) \
			"2.30258509299404568402"
#define EXSLT_LOG2E     (const xmlChar *) \
			"1.4426950408889634074"
#define EXSLT_SQRT1_2   (const xmlChar *) \
			"0.70710678118654752440"

/**
 * exsltMathConstant
 * @name: string
 * @precision:  number
 *
 * Implements the EXSLT - Math constant function:
 *     number math:constant(string, number)
 *
 * Returns a number value of the given constant with the given precision or
 * xmlXPathNAN if name is unknown.
 * The constants are PI, E, SQRRT2, LN2, LN10, LOG2E, and SQRT1_2
 */
static double
exsltMathConstant (xmlChar *name, double precision) {
    xmlChar *str;
    double ret;

    if ((name == NULL) || (xmlXPathIsNaN(precision)) || (precision < 1.0)) {
        return xmlXPathNAN;
    }

    if (xmlStrEqual(name, BAD_CAST "PI")) {
        int len = xmlStrlen(EXSLT_PI);

        if (precision <= len)
            len = (int)precision;

        str = xmlStrsub(EXSLT_PI, 0, len);

    } else if (xmlStrEqual(name, BAD_CAST "E")) {
        int len = xmlStrlen(EXSLT_E);

        if (precision <= len)
            len = (int)precision;

        str = xmlStrsub(EXSLT_E, 0, len);

    } else if (xmlStrEqual(name, BAD_CAST "SQRRT2")) {
        int len = xmlStrlen(EXSLT_SQRRT2);

        if (precision <= len)
            len = (int)precision;

        str = xmlStrsub(EXSLT_SQRRT2, 0, len);

    } else if (xmlStrEqual(name, BAD_CAST "LN2")) {
        int len = xmlStrlen(EXSLT_LN2);

        if (precision <= len)
            len = (int)precision;

        str = xmlStrsub(EXSLT_LN2, 0, len);

    } else if (xmlStrEqual(name, BAD_CAST "LN10")) {
        int len = xmlStrlen(EXSLT_LN10);

        if (precision <= len)
            len = (int)precision;

        str = xmlStrsub(EXSLT_LN10, 0, len);

    } else if (xmlStrEqual(name, BAD_CAST "LOG2E")) {
        int len = xmlStrlen(EXSLT_LOG2E);

        if (precision <= len)
            len = (int)precision;

        str = xmlStrsub(EXSLT_LOG2E, 0, len);

    } else if (xmlStrEqual(name, BAD_CAST "SQRT1_2")) {
        int len = xmlStrlen(EXSLT_SQRT1_2);

        if (precision <= len)
            len = (int)precision;

        str = xmlStrsub(EXSLT_SQRT1_2, 0, len);

    } else {
	str = NULL;
    }
    if (str == NULL)
        return xmlXPathNAN;
    ret = xmlXPathCastStringToNumber(str);
    xmlFree(str);
    return ret;
}

/**
 * exsltMathConstantFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathConstant for use by the XPath processor.
 */
static void
exsltMathConstantFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double   ret;
    xmlChar *name;

    if (nargs != 2) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    name = xmlXPathPopString(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathConstant(name, ret);
    if (name != NULL)
	xmlFree(name);

    xmlXPathReturnNumber(ctxt, ret);
}

#if defined(HAVE_STDLIB_H) && defined(RAND_MAX)

/**
 * exsltMathRandom:
 *
 * Implements the EXSLT - Math random() function:
 *    number math:random ()
 *
 * Returns a random number between 0 and 1 inclusive.
 */
static double
exsltMathRandom (void) {
    double ret;
    int num;

    num = rand();
    ret = (double)num / (double)RAND_MAX;
    return(ret);
}

/**
 * exsltMathRandomFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathRandom for use by the XPath processor.
 */
static void
exsltMathRandomFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 0) {
	xmlXPathSetArityError(ctxt);
	return;
    }

    ret = exsltMathRandom();

    xmlXPathReturnNumber(ctxt, ret);
}

#endif /* defined(HAVE_STDLIB_H) && defined(RAND_MAX) */

#if HAVE_MATH_H

/**
 * exsltMathAbs:
 * @num:  a double
 *
 * Implements the EXSLT - Math abs() function:
 *    number math:abs (number)
 *
 * Returns the absolute value of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathAbs (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = fabs(num);
    return(ret);
}

/**
 * exsltMathAbsFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathAbs for use by the XPath processor.
 */
static void
exsltMathAbsFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathAbs(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathSqrt:
 * @num:  a double
 *
 * Implements the EXSLT - Math sqrt() function:
 *    number math:sqrt (number)
 *
 * Returns the square root of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathSqrt (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = sqrt(num);
    return(ret);
}

/**
 * exsltMathSqrtFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathSqrt for use by the XPath processor.
 */
static void
exsltMathSqrtFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathSqrt(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathPower:
 * @base:  a double
 * @power:  a double
 *
 * Implements the EXSLT - Math power() function:
 *    number math:power (number, number)
 *
 * Returns the power base and power arguments, or xmlXPathNAN
 * if either @base or @power is Nan.
 */
static double
exsltMathPower (double base, double power) {
    double ret;

    if ((xmlXPathIsNaN(base) || xmlXPathIsNaN(power)))
	return(xmlXPathNAN);
    ret = pow(base, power);
    return(ret);
}

/**
 * exsltMathPower:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathPower for use by the XPath processor.
 */
static void
exsltMathPowerFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret, base;

    if (nargs != 2) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    /* power */
    base = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathPower(base, ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathLog:
 * @num:  a double
 *
 * Implements the EXSLT - Math log() function:
 *    number math:log (number)
 *
 * Returns the natural log of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathLog (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = log(num);
    return(ret);
}

/**
 * exsltMathLogFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathLog for use by the XPath processor.
 */
static void
exsltMathLogFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathLog(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathSin:
 * @num:  a double
 *
 * Implements the EXSLT - Math sin() function:
 *    number math:sin (number)
 *
 * Returns the sine of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathSin (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = sin(num);
    return(ret);
}

/**
 * exsltMathSinFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathSin for use by the XPath processor.
 */
static void
exsltMathSinFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathSin(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathCos:
 * @num:  a double
 *
 * Implements the EXSLT - Math cos() function:
 *    number math:cos (number)
 *
 * Returns the cosine of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathCos (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = cos(num);
    return(ret);
}

/**
 * exsltMathCosFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathCos for use by the XPath processor.
 */
static void
exsltMathCosFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathCos(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathTan:
 * @num:  a double
 *
 * Implements the EXSLT - Math tan() function:
 *    number math:tan (number)
 *
 * Returns the tangent of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathTan (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = tan(num);
    return(ret);
}

/**
 * exsltMathTanFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathTan for use by the XPath processor.
 */
static void
exsltMathTanFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathTan(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathAsin:
 * @num:  a double
 *
 * Implements the EXSLT - Math asin() function:
 *    number math:asin (number)
 *
 * Returns the arc sine of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathAsin (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = asin(num);
    return(ret);
}

/**
 * exsltMathAsinFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathAsin for use by the XPath processor.
 */
static void
exsltMathAsinFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathAsin(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathAcos:
 * @num:  a double
 *
 * Implements the EXSLT - Math acos() function:
 *    number math:acos (number)
 *
 * Returns the arc cosine of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathAcos (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = acos(num);
    return(ret);
}

/**
 * exsltMathAcosFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathAcos for use by the XPath processor.
 */
static void
exsltMathAcosFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathAcos(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathAtan:
 * @num:  a double
 *
 * Implements the EXSLT - Math atan() function:
 *    number math:atan (number)
 *
 * Returns the arc tangent of the argument, or xmlXPathNAN if @num is Nan.
 */
static double
exsltMathAtan (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = atan(num);
    return(ret);
}

/**
 * exsltMathAtanFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathAtan for use by the XPath processor.
 */
static void
exsltMathAtanFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathAtan(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathAtan2:
 * @y:  a double
 * @x:  a double
 *
 * Implements the EXSLT - Math atan2() function:
 *    number math:atan2 (number, number)
 *
 * Returns the arc tangent function of the y/x arguments, or xmlXPathNAN
 * if either @y or @x is Nan.
 */
static double
exsltMathAtan2 (double y, double x) {
    double ret;

    if ((xmlXPathIsNaN(y) || xmlXPathIsNaN(x)))
	return(xmlXPathNAN);
    ret = atan2(y, x);
    return(ret);
}

/**
 * exsltMathAtan2Function:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathAtan2 for use by the XPath processor.
 */
static void
exsltMathAtan2Function (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret, x;

    if (nargs != 2) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    x = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    /* y */
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathAtan2(ret, x);

    xmlXPathReturnNumber(ctxt, ret);
}

/**
 * exsltMathExp:
 * @num:  a double
 *
 * Implements the EXSLT - Math exp() function:
 *    number math:exp (number)
 *
 * Returns the exponential function of the argument, or xmlXPathNAN if
 * @num is Nan.
 */
static double
exsltMathExp (double num) {
    double ret;

    if (xmlXPathIsNaN(num))
	return(xmlXPathNAN);
    ret = exp(num);
    return(ret);
}

/**
 * exsltMathExpFunction:
 * @ctxt:  an XPath parser context
 * @nargs:  the number of arguments
 *
 * Wraps #exsltMathExp for use by the XPath processor.
 */
static void
exsltMathExpFunction (xmlXPathParserContextPtr ctxt, int nargs) {
    double ret;

    if (nargs != 1) {
	xmlXPathSetArityError(ctxt);
	return;
    }
    ret = xmlXPathPopNumber(ctxt);
    if (xmlXPathCheckError(ctxt))
	return;

    ret = exsltMathExp(ret);

    xmlXPathReturnNumber(ctxt, ret);
}

#endif /* HAVE_MATH_H */

/**
 * exsltMathRegister:
 *
 * Registers the EXSLT - Math module
 */

void
exsltMathRegister (void) {
    xsltRegisterExtModuleFunction ((const xmlChar *) "min",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathMinFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "max",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathMaxFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "highest",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathHighestFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "lowest",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathLowestFunction);
    /* register other math functions */
    xsltRegisterExtModuleFunction ((const xmlChar *) "constant",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathConstantFunction);
#ifdef HAVE_STDLIB_H
    xsltRegisterExtModuleFunction ((const xmlChar *) "random",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathRandomFunction);
#endif
#if HAVE_MATH_H
    xsltRegisterExtModuleFunction ((const xmlChar *) "abs",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathAbsFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "sqrt",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathSqrtFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "power",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathPowerFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "log",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathLogFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "sin",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathSinFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "cos",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathCosFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "tan",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathTanFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "asin",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathAsinFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "acos",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathAcosFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "atan",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathAtanFunction);
    xsltRegisterExtModuleFunction ((const xmlChar *) "atan2",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathAtan2Function);
    xsltRegisterExtModuleFunction ((const xmlChar *) "exp",
				   EXSLT_MATH_NAMESPACE,
				   exsltMathExpFunction);
#endif
}

/**
 * exsltMathXpathCtxtRegister:
 *
 * Registers the EXSLT - Math module for use outside XSLT
 */
int
exsltMathXpathCtxtRegister (xmlXPathContextPtr ctxt, const xmlChar *prefix)
{
    if (ctxt
        && prefix
        && !xmlXPathRegisterNs(ctxt,
                               prefix,
                               (const xmlChar *) EXSLT_MATH_NAMESPACE)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "min",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathMinFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "max",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathMaxFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "highest",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathHighestFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "lowest",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathLowestFunction)
#ifdef HAVE_STDLIB_H
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "random",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathRandomFunction)
#endif
#if HAVE_MATH_H
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "abs",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathAbsFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "sqrt",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathSqrtFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "power",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathPowerFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "log",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathLogFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "sin",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathSinFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "cos",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathCosFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "tan",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathTanFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "asin",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathAsinFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "acos",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathAcosFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "atan",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathAtanFunction)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "atan2",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathAtan2Function)
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "exp",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathExpFunction)
#endif
        && !xmlXPathRegisterFuncNS(ctxt,
                                   (const xmlChar *) "constant",
                                   (const xmlChar *) EXSLT_MATH_NAMESPACE,
                                   exsltMathConstantFunction)) {
        return 0;
    }
    return -1;
}