struct _String {
    u8[] cs;
    new _String={ u8[] b -> cs=b; };
    int _hashCode;
};

val _equals = { !_String !self, !_String s ->
    if( self == s ) return true;
    if( self.cs# != s.cs# ) return false;
    for( int i=0; i< self.cs#; i++ )
        if( self.cs[i] != s.cs[i] )
            return false;
    return true;
};

val _hashCode = { !_String self ->
    self._hashCode
    ?  self._hashCode
    : (self._hashCode = _hashCodeString(self));
};

val _hashCodeString = { !_String self ->
    int hash=0;
    if( self.cs ) {
        for( int i=0; i< self.cs#; i++ )
            hash = hash*31 + self.cs[i];
    }
    if( !hash ) hash = 123456789;
    return hash;
};

!_String !s = new _String(new u8[17]);
s.cs[0] =  67; // C
s.cs[1] = 108; // l
_hashCode(s);