2 variable switch loop

Question

Hi everyone,

Is it possible to use switch statement over if else when condition is made of 2 variables.

Thanks.

added:

foreach( DataRow row in workingTable.Rows )
        {                
            if( isKey && isValue )
                workingDictionary.Add( row[ keyIdentifier ].ToString(), row[ valueIdentifier ] );                            
            else if( isKey && !isValue )
                workingDictionary.Add( row[ keyIdentifier ].ToString(), row[ sValueIdentifier ] );                                                    
            else if( !isKey && isValue )
                workingDictionary.Add( row[ sKeyIdentifier ].ToString(), row[ valueIdentifier ] );                                                   
            else
                workingDictionary.Add( row[ sKeyIdentifier ].ToString(), row[ sValueIdentifier ] );                 
        }

Answer 1

That depends on the language – VB for example can theoretically do this, as can Ruby. For most other languages, one switch = one variable.

By the way, there’s no such thing as a “switch loop” (ignoring Duff’s device).

Answer 2

The switch statement is not a loop, it provides an alternative to using multiple if-else statements.

If you're asking can I use two variables in a switch statement, the answer is usually no but maybe you could combine the values to do something like in C#:

string sVal1 "abc", sVal2 = "xyz";
switch(sVal1 + "_" + sVal2)
{
    case "abc_xyz":
        // do something
        break;
    case "def_sdr":
        // do something
        break;
    default:
        // all else
        break;
}

Most likely in your case you're going to need to use to if-else statements. A switch is not what you want.

Answer 3

if isKey and isValue are bool castable to int, force them in respective bits.

unsigned char sw_var = isKey + 2*isValue;

Then sw_var is 0-3 depending on the booleans.

You can bind a number of bit fields that way:

unsigned long long bitfield = 
    key1 * (1ULL<<0)
  + key2 * (1ULL<<1)
  + key3 * (1ULL<<2)
  ...
  + key63 * (1ULL<<63);

(of course using all the resulting combinations a switch key would be extremely silly...)

Answer 4

Or you could rewrite the code something like this...

foreach( DataRow row in workingTable.Rows ) 
{
    int keyIndex = isKey ? keyIdentifier : sKeyIdentifier;
    int valueIndex = isValue ? valueIdentifier : sValueIdentifier;

    workingDictionary.Add( row[ keyIndex ].ToString(), row[ valueIndex ] );                             
}