org.openscience.cdk.math.FortranFormat Maven / Gradle / Ivy
/* Copyright (C) 1998-2007 Dan Gezelter
*
* Contact: [email protected]
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1
* of the License, or (at your option) any later version.
* All we ask is that proper credit is given for our work, which includes
* - but is not limited to - adding the above copyright notice to the beginning
* of your source code files, and to any copyright notice that you may distribute
* with programs based on this work.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*/
package org.openscience.cdk.math;
/**
* Converts a String representation of a Fortran double to a double.
*
* A modified version of the atof method provided in the Core Java
* books by Cay S. Horstmann & Gary Cornell. The main difference
* here is that we scan for Fortran double precision characters
* ('D' and 'd') which often cause the C versions of atof to
* barf.
*
* @author Dan Gezelter
*
* @cdk.module standard
* @cdk.githash
*/
public class FortranFormat {
/**
* Converts a string of digits to an double.
*
* @param s a string denoting a double
*/
public static double atof(String s) {
int i = 0;
int sign = 1;
double r = 0; // integer part
double p = 1; // exponent of fractional part
int state = 0; // 0 = int part, 1 = frac part
while (i < s.length() && Character.isWhitespace(s.charAt(i)))
i++;
if (i < s.length() && s.charAt(i) == '-') {
sign = -1;
i++;
} else if (i < s.length() && s.charAt(i) == '+') {
i++;
}
while (i < s.length()) {
char ch = s.charAt(i);
if ('0' <= ch && ch <= '9') {
if (state == 0)
r = r * 10 + ch - '0';
else if (state == 1) {
p = p / 10;
r = r + p * (ch - '0');
}
} else if (ch == '.') {
if (state == 0)
state = 1;
else
return sign * r;
} else if (ch == 'e' || ch == 'E' || ch == 'd' || ch == 'D') {
long e = (int) parseLong(s.substring(i + 1), 10);
return sign * r * Math.pow(10, e);
} else
return sign * r;
i++;
}
return sign * r;
}
private static long parseLong(String s, int base) {
int i = 0;
int sign = 1;
long r = 0;
while (i < s.length() && Character.isWhitespace(s.charAt(i)))
i++;
if (i < s.length() && s.charAt(i) == '-') {
sign = -1;
i++;
} else if (i < s.length() && s.charAt(i) == '+') {
i++;
}
while (i < s.length()) {
char ch = s.charAt(i);
if ('0' <= ch && ch < '0' + base)
r = r * base + ch - '0';
else if ('A' <= ch && ch < 'A' + base - 10)
r = r * base + ch - 'A' + 10;
else if ('a' <= ch && ch < 'a' + base - 10)
r = r * base + ch - 'a' + 10;
else
return r * sign;
i++;
}
return r * sign;
}
}