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/* Copyright (c) 1998, 1999, 2003, 2004 Lance Arsenault, (GNU GPL (v2+))
*/
/* class LogField: takes the log of the field passed to it. The log
* is computed at the time of the read() call. This does not store
* the field data in the LogField objects data, but just reads it from
* the Field object that was passed to it. The Field object that is
* passed to the constructor must stay valid for this to work.
*
*
* The function log(x) is not valid for x <= 0. So we need an error
* check.
*
*/
class LogField : public Field
{
public:
// value = count * scale + offset
inline LogField(Source *s, Field *f, value_t base=(value_t)10.0):
Field(s),
{
error = 0; // start with no error.
here lanceman
_isIncreasing = (scale > 0.0)? true: false;
_numberOfValues = MAXCOUNT;
_max = (_numberOfValues-1)*scale + offset;
_min = offset;
// assuming that count_t is unsigned so that -1 is the maxmum
// value
index = 0;
setName("linear field");
}
// read the list and advance the pointer to the next value in the
// series.
inline value_t read(void)
{
return scale*(index++) + offset;
}
// find the minimum values in the range of indexes
// indexing starts at 0.
inline value_t max(count_t i_max=((count_t) -1), count_t i_min=0)
{
if(i_max == ((count_t) -1))
i_max = _numberOfValues - 1;
if(scale > (value_t) 0.0)
return scale*(i_max) + offset;
else
return scale*(i_min) + offset;
}
// find the maximum values in the range of indexes
// indexing starts at 0.
inline value_t min(count_t i_max=((count_t) -1), count_t i_min=0)
{
if(i_max == ((count_t) -1))
i_max = _numberOfValues - 1;
if(scale < (value_t) 0.0)
return scale*(i_max) + offset;
else
return scale*(i_min) + offset;
}
// move the pointer to the first value.
inline void rewind(void) { index = 0; }
private:
// Index to the element to be read.
value_t base;
};
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