Question

Have some variables that I need to perform validation on. Pseudocode is as follows but I feel there must be a more elegant soloution.

  If ( var != A || var != B || var != C || var != D )
        {
        reject
        }
    else if ( var == A || var == B)
        {
        do validation applicable to A or B
        }
    else if ( var == A || var == B || var == C || var == D )  
        {
        do validation applicable to all valid vars
        }

Answer 1

The original pseudocode is incorrect, so I have made some reasonable assumptions about the required behaviour.

// If var not equal to any of A,B,C or D...
if ( var != A && var != B && var != C && var != D ) 
{
    reject
}
// Otherwise var equal to one of A,B,C or D
else
{
    // If it is A or B...
    if( var == A || var == B )
    {
        do validation applicable to A or B
    }

    do validation applicable to all valid vars
}

Or you could flip the logic as follows:

// If var equal to one of A,B,C or D
if( var == A || var == B || var == C || var == D ) 
{
    // If it is A or B...
    if( var == A || var == B )
    {
        do validation applicable to A or B
    }

    do validation applicable to all valid vars
}
else
{
    reject
}

which may be clearer.