Unit Converter Widget

I was wondering if someone had made a unit converter widget , a widget that can convert the input from a unit (say meters) to a relative unit (say millimeters) i am more interested on the algorithm that they used to support lots of units

baray98

I haven't done a general widget for unit conversion , so can't paste the code here.
But i had tried to generalize unit conversions. My skills were limited when i did this after Jacek had suggested me in this post.

I had come out with this some time back to help me convert between different units.
If some one has better idea, please do help so that i can improve my code too.

unit.h

Code:

---

#define MU0  12.566370614e-7          /* magnetic constant         */
#define C0   299792458.0              /* speed of light in vacuum  */
#define ZF0  376.73031346958504364963 /* wave resistance in vacuum */
 
namespace Units
{
  enum UnitType {
    Frequency=0,
    Length,
    Resistance,
    Angle,
    None = -1
  };
 
  enum FrequencyUnits {
    GHz=0,Hz,KHz,MHz
  };
 
  enum LengthUnits {
    mil=0,cm,mm,m,um,in,ft
  };
 
  enum ResistanceUnits {
    Ohm=0,kOhm
  };
 
  enum AngleUnits {
    Deg=0,Rad
  };
  const QStringList freqList(QStringList() << "GHz" << "Hz" << "kHz" << "MHz");
  const QStringList resList(QStringList() << "Ohm" << "kOhm");
  const QStringList lenList(QStringList() << "mil" << "cm" << "mm" << "m" << "um" << "in" << "ft");
  const QStringList angleList(QStringList() << "deg" << "rad");
 
  QString toString(FrequencyUnits f);
  QString toString(LengthUnits l);
  QString toString(ResistanceUnits r);
  QString toString(AngleUnits a);
  QString toString(int un,UnitType t);
  int toInt(const QString& unit);
  double convert(double value, Units::UnitType ut, int fromUnit, int toUnit);
};

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unit.cpp

Code:

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namespace Units
{
   // Unit conversion array for length.
   double lengthConversionTable[7][7] = {
      { 1.0,       2.54e-3,   2.54e-2,   2.54e-5,   25.4,     1.e-3,   1./12000},
      {1./2.54e-3,    1.0,     10.0,      1.e-2,    1.e4,   1./2.54,   1./30.48},
      {1./2.54e-2,  1./10.,     1.0,       1.e-3,   1.e3,   1./25.4,   1./304.8},
      {1./2.54e-5,    1.e2,    1.e3,         1.0,   1.e6,  1./2.54e-2, 1./0.3048},
      {1./25.4,      1.e-4,   1.e-3,       1.e-6,    1.0,  1./2.54e4,  1./3.048e5},
      {1.e3,          2.54,    25.4,     2.54e-2, 2.54e4,        1.0,    1./12.},
      {1.2e4,        30.48,   304.8,      0.3048, 3.048e5,      12.0,       1.0}
   };
 
   // Unit conversion array for frequencies.
   double frequencyConversionTable[4][4] = {
      { 1.0,     1.e9,     1.e6,      1.e3},
      { 1.e-9,   1.0,      1.e-3,     1.e-6},
      { 1.e-6,   1.e3,     1.0,       1.e-3},
      { 1.e-3,   1.e6,     1.e3,      1.0}
   };
 
   // Unit conversion array for resistances.
   double resistanceConversionTable[2][2] = {
      {1.0,    1.e-3},
      {1.e3,   1.0}
   };
 
   // Unit conversion array for angles.
   double angleConversionTable[2][2] = {
      {1.0,         M_PI/180.0},
      {180.0/M_PI,         1.0}
   };
 
   QString toString(FrequencyUnits f)
   {
      return Units::freqList[int(f)];
   }
   QString toString(LengthUnits l)
   {
      return Units::lenList[int(l)];
   }
   QString toString(ResistanceUnits r)
   {
      return Units::resList[int(r)];
   }
   QString toString(AngleUnits a)
   {
      return Units::angleList[int(a)];
   }
 
   QString toString(int u, UnitType t)
   {
      switch(t) {
         case Frequency:
            return toString(FrequencyUnits(u));
         case Length:
            return toString(LengthUnits(u));
         case Resistance:
            return toString(ResistanceUnits(u));
         case Angle:
            return toString(AngleUnits(u));
         default:
            return QString();
      };
   }
 
   double convert(double value, Units::UnitType ut, int fromUnit, int toUnit)
   {
      double cnv = value;
      switch(ut)
      {
         case Frequency:
            cnv *= frequencyConversionTable[int(fromUnit)][toUnit];
            break;
         case Length:
            cnv *= lengthConversionTable[int(fromUnit)][toUnit];
            break;
         case Resistance:
            cnv *= resistanceConversionTable[int(fromUnit)][toUnit];
            break;
         case Angle:
            cnv *= angleConversionTable[int(fromUnit)][toUnit];
            break;
         default:
            break;
      };
      return cnv;
   }
 
   int toInt(const QString& unit)
   {
      if(unit == "NA")
         return None;
      for(int i=0; i<freqList.size(); ++i)
      {
         if(unit == freqList[i])
            return i;
      }
      for(int i=0; i<lenList.size(); ++i)
      {
         if(unit == lenList[i])
            return i;
      }
      for(int i=0; i<resList.size(); ++i)
      {
         if(unit == resList[i])
            return i;
      }
      for(int i=0; i<angleList.size(); ++i)
      {
         if(unit == angleList[i])
            return i;
      }
      return None;
   }
};

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I think the best way would be to have a class (but not a widget) that reads definitions and formulas from an XML or ini file. Then it's just a matter of finding a proper formula, parsing and executing it. You can even keep scripts in the file and execute them using the script engine Qt provides.

Gopala I am lost in generating a temperatureConversion table

I need it in Celsius , Farenheit, Kelvin


hope you can help me out

baray98

Quote:

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Originally Posted by baray98

Gopala I am lost in generating a temperatureConversion table

I need it in Celsius , Farenheit, Kelvin


hope you can help me out

baray98

---

I had done this some time before. May be this can be improved.

Code:

---

enum TemperatureUnit {
  Celsius,
  Farenheit,
  Kelvin
};
 
double convert(double val, TemperatureUnit from, TemperatureUnit to)
{
  if(from == Celsius) {
	if(to == Kelvin)
	  return val + 273.15;
	else if(to == Farenheit)
	  return 1.8*val + 32;
	else
	  return val;
  }
  else if(from == Farenheit) {
	if(to == Celsius)
	  return (val - 32)*1.8;
	else if(to == Kelvin)
	  return (val - 32)*1.8 + 273.15;
	else
	  return val;
  }
  else {
	if(to == Celsius)
	  return val - 273.15;
	else if(to == Farenheit)
	  return (val-273.15)*1.8 + 32;
	else
	  return val;
  }
}

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Isn't this by any chance an academic/school problem?

Quote:

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Isn't this by any chance an academic/school problem?

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I'd even say this is not a programming issue, this should be posted on a school math forum.
Once you have the formula, what is there to do? "hack" the "code"?
Come on...

I tought there was a way of converting temp using some kinda table but, thank you

baray98

I made a Quantity class that did conversions for me, with Weight and Volume subclasses. It was based on Fowler's Quantity Analysis Pattern. You can get it at <http://www.usermode.org/code/quantity-0.1.tar.gz>.

Quote:

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Originally Posted by baray98

I tought there was a way of converting temp using some kinda table but, thank you

baray98

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Do you think is it ever possible ? :rolleyes:

Quote:

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Do you think is it ever possible ?

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For a defined range and resolution - sure!
Actually used by time critical applications, since its only a LUT lookup instead of a calculation.

Like a multiplication table from school ;)

i want to know what is the main code for mm to cm to m widget .. gopala krishna can you help me with that.

Quote:

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gopala krishna can you help me with that.

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Really? You think digging up an 8 year old thread and asking one of the posters is going to help?

1 m = 100 cm = 1000 mm

It's a couple of lines of code - what would be the point of a widget to do that? Maybe you should be a little more clear about what it is you actually want to do.

Is this a homework project by any chance?