double s_to_r8 ( char *s, int *lchar, int *error )
/******************************************************************************/
/*
Purpose:
S_TO_R8 reads an R8 value from a string.
Discussion:
We have had some trouble with input of the form 1.0E-312.
For now, let's assume anything less than 1.0E-20 is zero.
This routine will read as many characters as possible until it reaches
the end of the string, or encounters a character which cannot be
part of the real number.
Legal input is:
1 blanks,
2 '+' or '-' sign,
2.5 spaces
3 integer part,
4 decimal point,
5 fraction part,
6 'E' or 'e' or 'D' or 'd', exponent marker,
7 exponent sign,
8 exponent integer part,
9 exponent decimal point,
10 exponent fraction part,
11 blanks,
12 final comma or semicolon.
with most quantities optional.
Example:
S R
'1' 1.0
' 1 ' 1.0
'1A' 1.0
'12,34,56' 12.0
' 34 7' 34.0
'-1E2ABCD' -100.0
'-1X2ABCD' -1.0
' 2E-1' 0.2
'23.45' 23.45
'-4.2E+2' -420.0
'17d2' 1700.0
'-14e-2' -0.14
'e2' 100.0
'-12.73e-9.23' -12.73 * 10.0^(-9.23)
Licensing:
This code is distributed under the GNU LGPL license.
Modified:
24 June 2005
Author:
John Burkardt
Parameters:
Input, char *S, the string containing the
data to be read. Reading will begin at position 1 and
terminate at the end of the string, or when no more
characters can be read to form a legal real. Blanks,
commas, or other nonnumeric data will, in particular,
cause the conversion to halt.
Output, int *LCHAR, the number of characters read from
the string to form the number, including any terminating
characters such as a trailing comma or blanks.
Output, int *ERROR, is TRUE (1) if an error occurred and FALSE (0)
otherwise.
Output, double S_TO_R8, the value that was read from the string.
*/
{
char c;
int ihave;
int isgn;
int iterm;
int jbot;
int jsgn;
int jtop;
int nchar;
int ndig;
double r;
double rbot;
double rexp;
double rtop;
char TAB = 9;
nchar = s_len_trim ( s );
*error = 0;
r = 0.0;
*lchar = -1;
isgn = 1;
rtop = 0.0;
rbot = 1.0;
jsgn = 1;
jtop = 0;
jbot = 1;
ihave = 1;
iterm = 0;
for ( ; ; )
{
c = s[*lchar+1];
*lchar = *lchar + 1;
/*
Blank or TAB character.
*/
if ( c == ' ' || c == TAB )
{
if ( ihave == 2 )
{
}
else if ( ihave == 6 || ihave == 7 )
{
iterm = 1;
}
else if ( 1 < ihave )
{
ihave = 11;
}
}
/*
Comma.
*/
else if ( c == ',' || c == ';' )
{
if ( ihave != 1 )
{
iterm = 1;
ihave = 12;
*lchar = *lchar + 1;
}
}
/*
Minus sign.
*/
else if ( c == '-' )
{
if ( ihave == 1 )
{
ihave = 2;
isgn = -1;
}
else if ( ihave == 6 )
{
ihave = 7;
jsgn = -1;
}
else
{
iterm = 1;
}
}
/*
Plus sign.
*/
else if ( c == '+' )
{
if ( ihave == 1 )
{
ihave = 2;
}
else if ( ihave == 6 )
{
ihave = 7;
}
else
{
iterm = 1;
}
}
/*
Decimal point.
*/
else if ( c == '.' )
{
if ( ihave < 4 )
{
ihave = 4;
}
else if ( 6 <= ihave && ihave <= 8 )
{
ihave = 9;
}
else
{
iterm = 1;
}
}
/*
Exponent marker.
*/
else if ( ch_eqi ( c, 'E' ) || ch_eqi ( c, 'D' ) )
{
if ( ihave < 6 )
{
ihave = 6;
}
else
{
iterm = 1;
}
}
/*
Digit.
*/
else if ( ihave < 11 && '0' <= c && c <= '9' )
{
if ( ihave <= 2 )
{
ihave = 3;
}
else if ( ihave == 4 )
{
ihave = 5;
}
else if ( ihave == 6 || ihave == 7 )
{
ihave = 8;
}
else if ( ihave == 9 )
{
ihave = 10;
}
ndig = ch_to_digit ( c );
if ( ihave == 3 )
{
rtop = 10.0 * rtop + ( double ) ndig;
}
else if ( ihave == 5 )
{
rtop = 10.0 * rtop + ( double ) ndig;
rbot = 10.0 * rbot;
}
else if ( ihave == 8 )
{
jtop = 10 * jtop + ndig;
}
else if ( ihave == 10 )
{
jtop = 10 * jtop + ndig;
jbot = 10 * jbot;
}
}
/*
Anything else is regarded as a terminator.
*/
else
{
iterm = 1;
}
/*
If we haven't seen a terminator, and we haven't examined the
entire string, go get the next character.
*/
if ( iterm == 1 || nchar <= *lchar + 1 )
{
break;
}
}
/*
If we haven't seen a terminator, and we have examined the
entire string, then we're done, and LCHAR is equal to NCHAR.
*/
if ( iterm != 1 && (*lchar) + 1 == nchar )
{
*lchar = nchar;
}
/*
Number seems to have terminated. Have we got a legal number?
Not if we terminated in states 1, 2, 6 or 7!
*/
if ( ihave == 1 || ihave == 2 || ihave == 6 || ihave == 7 )
{
*error = 1;
return r;
}
/*
Number seems OK. Form it.
We have had some trouble with input of the form 1.0E-312.
For now, let's assume anything less than 1.0E-20 is zero.
*/
if ( jtop == 0 )
{
rexp = 1.0;
}
else
{
if ( jbot == 1 )
{
if ( jsgn * jtop < -20 )
{
rexp = 0.0;
}
else
{
rexp = pow ( ( double ) 10.0, ( double ) ( jsgn * jtop ) );
}
}
else
{
if ( jsgn * jtop < -20 * jbot )
{
rexp = 0.0;
}
else
{
rexp = jsgn * jtop;
rexp = rexp / jbot;
rexp = pow ( ( double ) 10.0, ( double ) rexp );
}
}
}
r = isgn * rexp * rtop / rbot;
return r;
}
double s_to_r8 ( std::string s, int *lchar, bool *error )
{
char c;
int ihave;
int isgn;
int iterm;
int jbot;
int jsgn;
int jtop;
int nchar;
int ndig;
double r;
double rbot;
double rexp;
double rtop;
char TAB = 9;
nchar = s_len_trim ( s );
*error = false;
r = 0.0;
*lchar = -1;
isgn = 1;
rtop = 0.0;
rbot = 1.0;
jsgn = 1;
jtop = 0;
jbot = 1;
ihave = 1;
iterm = 0;
for ( ; ; )
{
c = s[*lchar+1];
*lchar = *lchar + 1;
//
// Blank or TAB character.
//
if ( c == ' ' || c == TAB )
{
if ( ihave == 2 )
{
}
else if ( ihave == 6 || ihave == 7 )
{
iterm = 1;
}
else if ( 1 < ihave )
{
ihave = 11;
}
}
//
// Comma.
//
else if ( c == ',' || c == ';' )
{
if ( ihave != 1 )
{
iterm = 1;
ihave = 12;
*lchar = *lchar + 1;
}
}
//
// Minus sign.
//
else if ( c == '-' )
{
if ( ihave == 1 )
{
ihave = 2;
isgn = -1;
}
else if ( ihave == 6 )
{
ihave = 7;
jsgn = -1;
}
else
{
iterm = 1;
}
}
//
// Plus sign.
//
else if ( c == '+' )
{
if ( ihave == 1 )
{
ihave = 2;
}
else if ( ihave == 6 )
{
ihave = 7;
}
else
{
iterm = 1;
}
}
//
// Decimal point.
//
else if ( c == '.' )
{
if ( ihave < 4 )
{
ihave = 4;
}
else if ( 6 <= ihave && ihave <= 8 )
{
ihave = 9;
}
else
{
iterm = 1;
}
}
//
// Exponent marker.
//
else if ( ch_eqi ( c, 'E' ) || ch_eqi ( c, 'D' ) )
{
if ( ihave < 6 )
{
ihave = 6;
}
else
{
iterm = 1;
}
}
//
// Digit.
//
else if ( ihave < 11 && '0' <= c && c <= '9' )
{
if ( ihave <= 2 )
{
ihave = 3;
}
else if ( ihave == 4 )
{
ihave = 5;
}
else if ( ihave == 6 || ihave == 7 )
{
ihave = 8;
}
else if ( ihave == 9 )
{
ihave = 10;
}
ndig = ch_to_digit ( c );
if ( ihave == 3 )
{
rtop = 10.0 * rtop + ( double ) ndig;
}
else if ( ihave == 5 )
{
rtop = 10.0 * rtop + ( double ) ndig;
rbot = 10.0 * rbot;
}
else if ( ihave == 8 )
{
jtop = 10 * jtop + ndig;
}
else if ( ihave == 10 )
{
jtop = 10 * jtop + ndig;
jbot = 10 * jbot;
}
}
//
// Anything else is regarded as a terminator.
//
else
{
iterm = 1;
}
//
// If we haven't seen a terminator, and we haven't examined the
// entire std::string, go get the next character.
//
if ( iterm == 1 || nchar <= *lchar + 1 )
{
break;
}
}
//
// If we haven't seen a terminator, and we have examined the
// entire std::string, then we're done, and LCHAR is equal to NCHAR.
//
if ( iterm != 1 && (*lchar) + 1 == nchar )
{
*lchar = nchar;
}
//
// Number seems to have terminated. Have we got a legal number?
// Not if we terminated in states 1, 2, 6 or 7!
//
if ( ihave == 1 || ihave == 2 || ihave == 6 || ihave == 7 )
{
*error = true;
return r;
}
//
// Number seems OK. Form it.
//
if ( jtop == 0 )
{
rexp = 1.0;
}
else
{
if ( jbot == 1 )
{
rexp = pow ( 10.0, jsgn * jtop );
}
else
{
rexp = jsgn * jtop;
rexp = rexp / jbot;
rexp = pow ( 10.0, rexp );
}
}
r = isgn * rexp * rtop / rbot;
return r;
}