THcParmList.cxx

/** \class THcParmList
    \ingroup Base

A THcParmList object holds an arbitrary list of parameters and
their values.  Parameters may be integers, real numbers or strings.
Integers and floating point numbers can be one dimensional arrays.
(Strings can not be arrays.)  In addition to values, each parameter
may have a title/description.  (No titles are saved for string parameters.)

The Hall C analyzer make one instance of this class available via the
global `gHcParms`.  The detector classes look for their
configuration parameters in that list.

This class is built on THaVarList, adding a method to load the list of
parameters from Hall C ENGINE style CTP parameter files and a method
to retrieve a set of parameters from the list.

An instance of THaTextvars is created to hold the string parameters.

*/

#define INCLUDESTR "#include"

#include "TObjArray.h"
#include "TObjString.h"
#include "TSystem.h"

#include "THcParmList.h"
#include "THaVar.h"
#include "THaFormula.h"

#include "TMath.h"

/* #incluce <algorithm> include <fstream> include <cstring> */
#include <iostream>
#include <fstream>
#include <cassert>
#include <cstdlib>
#include <stdexcept>

using namespace std;
Int_t  fDebug   = 1;  // Keep this at one while we're working on the code    

ClassImp(THcParmList)

/// Create empty numerical and string parameter lists
THcParmList::THcParmList() : THaVarList()
{
  TextList = new THaTextvars;
}

inline static bool IsComment( const string& s, string::size_type pos )
{
  return ( pos != string::npos && pos < s.length() &&
	   (s[pos] == '#' || s[pos] == ';' || s.substr(pos,2) == "//") );
}

void THcParmList::Load( const char* fname, Int_t RunNumber )
{
  /**
Load the parameter cache by reading a CTP style parameter file.  Most
parameter files used in the ENGINE should work.

A line in the file of the form
~~~
   varname = value1[, value2, value3, value4]  [; Comment]
~~~
adds the variable `varname` to the parameter cache and the value after
the equal sign is stored.  If a list of values is given, then the
values are saved as an array.  Lists of values may be continued on
additional lines.  Lines without a `=` are interpreted as such continuation
lines.  Text after a ";" is treated as a comment.  If this comment is
on a line defining a parameter, then it is saved as the
title/description for the parameter.

Values may be expressions composed of numbers and previously defined
parameters.  These expressions are evaluated with THaFormula.

Lines of the form
~~~
   varname = "A string"
~~~
or
~~~
   varname = 'A string'
~~~
create string parameters.

A parameter file can load other files with the include statement
~~~
   #include "filename"
~~~

The ENGINE CTP support parameter "blocks" which were marked with
`begin` and `end` statements.  These statements are ignored.

  */

  static const char* const whtspc = " \t";

  ifstream ifiles[100];		// Should use stack instead

  Int_t nfiles=0;
  ifiles[nfiles].open(fname);
  if(ifiles[nfiles].is_open()) {
    cout << "Opening parameter file: [" << nfiles << "] " << fname << endl;
    nfiles++;
  }

  if(!nfiles) {
    static const char* const here   = "THcParmList::LoadFromFile";
    Error (here, "error opening parameter file %s",fname);
    return;			// Need a success argument returned
  }
  
  string line;
  char varname[100];
  Int_t InRunRange;
  Int_t currentindex = 0;

  varname[0] = '\0';

  if(RunNumber > 0) {
    InRunRange = 0;		// Wait until run number range matching RunNumber is found
    cout << "Reading Parameters for run " << RunNumber << endl;
  } else {
    InRunRange = 1;		// Interpret all lines
  }

  while(nfiles) {
    string current_comment("");
    // EJB_Note:  existing_comment is never used.
    // string existing_comment("");
    string::size_type start, pos = 0;

    if(!getline(ifiles[nfiles-1],line)) {
      ifiles[nfiles-1].close();
      nfiles--;
      //      cout << nfiles << ": " << "Closed" << endl;
      continue;
    }
    // Look for include statement
    if(line.compare(0,strlen(INCLUDESTR),INCLUDESTR)==0) {
      line.erase(0,strlen(INCLUDESTR));
      pos = line.find_first_not_of(whtspc);
      // Strip leading white space
      if(pos != string::npos && pos > 0 && pos < line.length()) {
	line.erase(0,pos);
      }
      char quotechar=line[0];
      if(quotechar == '"' || quotechar == '\'') {
	line.erase(0,1);
	line.erase(line.find_first_of(quotechar));
      } else {
	line.erase(line.find_first_of(whtspc));
      }
      //      cout << line << endl;
      ifiles[nfiles].open(line.c_str());
      if(ifiles[nfiles].is_open()) {
	cout << "Opening parameter file: [" << nfiles << "] " << line << endl;
	nfiles++;
      }
      continue;
    }

    // Blank line or comment?
    if( line.empty()
	|| (start = line.find_first_not_of( whtspc )) == string::npos
	|| IsComment(line, start) )
      continue;

    // Get rid of trailing comments and leading and trailing whitespace
    // Need to save the comment and put it in the thVar
    
    while( (pos = line.find_first_of("#;/", pos+1)) != string::npos ) {
      if( IsComment(line, pos) ) {
	current_comment.assign(line,pos+1,line.length());
	line.erase(pos);	// Strip off comment
	// Strip leading white space from comment
	//cout << "CommentA: " << current_comment << endl;
	pos = current_comment.find_first_not_of(whtspc);
	if(pos!=string::npos && pos > 0 && pos < current_comment.length()) {
	  current_comment.erase(0,pos);
	}
	//cout << "CommentB: " << current_comment << endl;
	break;
      }
    }
    pos = line.find_last_not_of( whtspc );
    assert( pos != string::npos );
    if( pos != string::npos && ++pos < line.length() )
      line.erase(pos);
    pos = line.find_first_not_of(whtspc);
    // Strip leading white space
    if(pos != string::npos && pos > 0 && pos < line.length()) {
      line.erase(0,pos);
    }
    // Ignore begin and end statements
    if(line.compare(0,5,"begin")==0 ||
       line.compare(0,3,"end")==0) {
      cout << "Skipping: " << line << endl;
      continue;
    }

    // Get rid of all white space not in quotes
    // Step through one char at a time 
    pos = 0;
    int inquote=0;
    char quotechar=' ';
    // cout << "Unstripped line: |" << line << "|" << endl;
    while(pos<line.length()) {
      if(inquote) {
	if(line[pos++] == quotechar) { // Possibly end of quoted string
	  if(line[pos] == quotechar) { // Protected quote
	    pos++;		// Skip the protected quote
	  } else {		// End of quoted string
	    inquote = 0;
	    quotechar = ' ';
	    pos++;
	  }
	}
      } else {
	if(line[pos] == ' ' || line[pos] == '\t') {
	  line.erase(pos,1);
	} else if(line[pos] == '"' || line[pos] == '\'') {
	  quotechar = line[pos++];\
	  inquote = 1;
	} else {
	  pos++;
	}
      }
    }
    // cout << "Stripped line: |" << line << "|" << endl;

    // Need to do something to bug out if line is empty

    // If in Engine database mode, check if line is a number range AAAA-BBBB
    if(RunNumber>0) {
      if(line.find_first_not_of("0123456789-")==string::npos) { // Interpret as runnum range
	if( (pos=line.find_first_of("-")) != string::npos) {
	  Int_t RangeStart=atoi(line.substr(0,pos).c_str());
	  Int_t RangeEnd=atoi(line.substr(pos+1,string::npos).c_str());
	  if(RunNumber >= RangeStart && RunNumber <= RangeEnd) {
	    InRunRange = 1;
	  } else {
	    InRunRange = 0;
	  }
	} else {		// A single number.  Run 
	  if(atoi(line.c_str()) == RunNumber) {
	    InRunRange = 1;
	  } else {
	    InRunRange = 0;
	  }
	}
	continue;		// Skip to next line
      }
    }

    if(!InRunRange) continue;

    // Interpret left of = as var name
    Int_t valuestartpos=0;  // Stays zero if no = found
    Int_t ttype = 0;     // Are any of the values floating point?
    if((pos=line.find_first_of("="))!=string::npos) {
      strcpy(varname, (line.substr(0,pos)).c_str());
      valuestartpos = pos+1;
      currentindex = 0;
    }

    // If first char after = is a quote, then this is a string assignment
    if(line[valuestartpos] == '"' || line[valuestartpos] == '\'') {
      quotechar = line[valuestartpos++];
      // Scan until end of line or terminating quote
      //      valuestartpos++;
      pos = valuestartpos;
      while(pos<line.length()) {
	if(line[pos++] == quotechar) { // Possibly end of quoted string
	  if(line[pos] == quotechar) { // Protected quote
	    pos++;
	  } else {
	    pos--;
	    break;
	  }
	}
      }
      if(TextList) {
	// Should check that a numerical assignment doesn't exist, but for
	// now, the same variable name can be used for strings and numbers
	string varnames(varname);
	AddString(varnames, line.substr(valuestartpos,pos-valuestartpos));
      }
      continue;
    }
      
    TString values((line.substr(valuestartpos)).c_str());
    TObjArray *vararr = values.Tokenize(",");
    Int_t nvals = vararr->GetLast()+1;
    
    Int_t* ip=0;
    Double_t* fp=0;
    // or expressions
    for(Int_t i=0;(ttype==0&&i<nvals);i++) {
      TString valstr = ((TObjString *)vararr->At(i))->GetString();
      if(valstr.IsFloat()) {	// Is a number
	if(valstr.Contains(".") || valstr.Contains("e",TString::kIgnoreCase)) {
	  ttype = 1;
	  break;
	}
      } else {
	ttype = 2;		// Force float if expression or Var
	break;
      }
    }

    // New pseudo code
    // currentindex = where next item goes
    // nvals = number of new items on line
    // newlength = curentindex+nvals

    // if (variable already exists)   (valuestartpos is 0 or a find succeeded)
    //       get existinglegnth
    //       if (existinglength > newlength && type doesn't change) {
    //            copy nvals values directly into array
    //       else
    //            make new longer array of length max(existinglength, newlength)
    //            copy existinglength values into longer array changing type if needed
    //            delete old varname
    //            recreate varname of proper length
    // else (variable doesn't exist)
    //      make array of newlength
    //      create varname
    //  
    // There is some code duplication here.  Refactor later

    Int_t newlength = currentindex + nvals;
    THaVar* existingvar=Find(varname);
    if(existingvar) {
      string existingcomment;
      existingcomment.assign(existingvar->GetTitle());
      if(!existingcomment.empty()) {
	current_comment.assign(existingcomment);
      }
      Int_t existingtype=existingvar->GetType();
      Int_t existinglength=existingvar->GetLen();
      if(newlength > existinglength ||
	 (existingtype == kInt && ttype > 0)) { // Length or type change needed
	if(newlength < existinglength) newlength = existinglength;
	Int_t newtype=-1;
	if(ttype>0 || existingtype == kDouble) {
	  newtype = kDouble;
	  fp = new Double_t[newlength];
	  if(existingtype == kDouble) {
	    Double_t* existingp= (Double_t*) existingvar->GetValuePointer();
	    for(Int_t i=0;i<existinglength;i++) {
	      fp[i] = existingp[i];
	    }
	  } else if(existingtype == kInt) {
	    Int_t* existingp= (Int_t*) existingvar->GetValuePointer();
	    for(Int_t i=0;i<existinglength;i++) {
	      fp[i] = existingp[i];
	    }
	  } else {
	    cout << "Whoops!" << endl;
	  }
	} else if(existingtype == kInt) {	// Stays int
	  newtype = kInt;
	  ip = new Int_t[newlength];
	  Int_t* existingp= (Int_t*) existingvar->GetValuePointer();
	  for(Int_t i=0;i<existinglength;i++) {
	    ip[i] = existingp[i];
	  }
	} else {
	  cout << "Whoops!" << endl;
	}
	// Now copy new values in
	for(Int_t i=0;i<nvals;i++) {
	  TString valstr = ((TObjString *)vararr->At(i))->GetString();
	  if(newtype == kInt) {
	    ip[currentindex+i] = valstr.Atoi();
	  } else {
	    if(valstr.IsFloat()) {
	      fp[currentindex+i] = valstr.Atof();
	    } else {
	      THaFormula* formula = new THaFormula
		("temp",valstr.Data(), (Bool_t) 0, this, 0);
	      fp[currentindex+i] = formula->Eval();
	      delete formula;
	    }
	  }
	}
	currentindex += nvals;
	// Remove old variable and recreate
	if(existingtype == kDouble) {
	  delete [] (Double_t*) existingvar->GetValuePointer();
	} else if (existingtype == kInt) {
	  delete [] (Int_t*) existingvar->GetValuePointer();
	}
	RemoveName(varname);
	char *arrayname=new char [strlen(varname)+20];
	sprintf(arrayname,"%s[%d]",varname,newlength);
	if(newtype == kInt) {
	  Define(arrayname, current_comment.c_str(), *ip);
	} else {
	  Define(arrayname, current_comment.c_str(), *fp);
	}
	delete[] arrayname;
      } else {
	// Existing array long enough and of right type, just copy to it.
	if(ttype == 0 && existingtype == kInt) {
	  Int_t* existingp= (Int_t*) existingvar->GetValuePointer();
	  for(Int_t i=0;i<nvals;i++) {
	    TString valstr = ((TObjString *)vararr->At(i))->GetString();
	    existingp[currentindex+i] = valstr.Atoi();
	  }
	} else {
	  Double_t* existingp= (Double_t*) existingvar->GetValuePointer();
	  for(Int_t i=0;i<nvals;i++) {
	    TString valstr = ((TObjString *)vararr->At(i))->GetString();
	    if(valstr.IsFloat()) {
	      existingp[currentindex+i] = valstr.Atof();
	    } else {
	      THaFormula* formula = new THaFormula
		("temp",valstr.Data(), (Bool_t) 0, this, 0);
	      existingp[currentindex+i] = formula->Eval();
	      delete formula;
	    }
	  }
	}
	currentindex += nvals;
      }	
    } else {
      if(currentindex !=0) {
	cout << "currentindex=" << currentindex << " shouldn't be!" << endl;
      }
      if(ttype==0) {
	ip = new Int_t[nvals];
      } else {
	fp = new Double_t[nvals];
      }
      for(Int_t i=0;i<nvals;i++) {
	TString valstr = ((TObjString *)vararr->At(i))->GetString();
	if(ttype==0) {
	  ip[i] = valstr.Atoi();
	} else {
	  if(valstr.IsFloat()) {
	    fp[i] = valstr.Atof();
	  } else {
	    THaFormula* formula = new THaFormula
	      ("temp",valstr.Data(), (Bool_t) 0, this, 0);
	    fp[i] = formula->Eval();
	    delete formula;
	  }
	}
      }
      currentindex = nvals;
      
      char *arrayname=new char [strlen(varname)+20];
      sprintf(arrayname,"%s[%d]",varname,nvals);
      if(ttype==0) {
	Define(arrayname, current_comment.c_str(), *ip);
      } else {
	Define(arrayname, current_comment.c_str(), *fp);
      }
      delete[] arrayname;
    }

    delete vararr;		// Discard result of Tokenize

    //    cout << line << endl;

  }

  return;

}
//_____________________________________________________________________________
Int_t THcParmList::LoadParmValues(const DBRequest* list, const char* prefix)
{
  /**

Retrieve parameter values from the parameter cache.

The following example loads several parameters held in the `gHcParms`
parameter cache into scalar variables or arrays.
~~~
  DBRequest list[]={
    {"nplanes", &fNPlanes, kInt},
    {"name", &fName, kString},
    {"array", fArray, kDouble, fArraySize},
    {"optional", &FOptionalvar, kDouble, 0, 1},
    {0}
  };
  gHcParms->LoadParmValues((DBRequest*)&list,"h");
~~~
If a string is passed as the second parameter of LoadParmValues, then
that string is prepended to the parameter names given in the DBRequest
list.  In the above example, the values for the parameters `hnplanes`,
`hname`, `harray`, and `hoptional` are loaded.

If a requested parameter is not found in the parameter cache, an error
is printed.  If the 5th element of a DBRequest structure is true (non
zero), then there will be no error if the parameter is missing.

  */
  
  const DBRequest *ti = list;
  Int_t cnt=0;
  Int_t this_cnt=0;

  if( !prefix ) prefix = "";

  while ( ti && ti->name ) {
    string keystr(prefix); keystr.append(ti->name);
    const char* key = keystr.c_str();
    //    cout <<"Now at "<<ti->name<<endl;
    this_cnt = 0;
    if(this->Find(key)) {
      VarType ty = this->Find(key)->GetType();
      if (ti->nelem>1) {
	// it is an array, use the appropriateinterface
	switch (ti->type) {
	case (kDouble) :
	  this_cnt = GetArray(key,static_cast<Double_t*>(ti->var),ti->nelem);
	  break;
	case (kInt) :
	  this_cnt = GetArray(key,static_cast<Int_t*>(ti->var),ti->nelem);
	  break;
	default:
	  Error("THcParmList","Invalid type to read %s",key);
	  break;
	}

      } else {
	switch (ti->type) {
	case (kDouble) :
	  if(ty == kInt) {
	    *static_cast<Double_t*>(ti->var)=*(Int_t *)this->Find(key)->GetValuePointer();	    
	  } else if (ty == kDouble) {
	    *static_cast<Double_t*>(ti->var)=*(Double_t *)this->Find(key)->GetValuePointer();
	  } else {
	    cout << "*** ERROR!!! Type Mismatch " << key << endl;
	  }
	  this_cnt=1;

	  break;
	case (kInt) :
	  if(ty == kInt) {
	    *static_cast<Int_t*>(ti->var)=*(Int_t *)this->Find(key)->GetValuePointer();
	  } else if (ty == kDouble) {
	    *static_cast<Int_t*>(ti->var)=TMath::Nint(*(Double_t *)this->Find(key)->GetValuePointer());
	    cout << "*** WARNING!!!  Rounded " << key << " to nearest integer " << endl;
	  } else {
	    cout << "*** ERROR!!! Type Mismatch " << key << endl;
	  }
	  this_cnt=1;
	  break;
	default:
	  Error("THcParmList","Invalid type to read %s",key);
	  break;
	}
      }
    } else {			// See if it is a text variable
      const char* value = GetString(key);
      if(value) {
	this_cnt = 1;
	if(ti->type == kString) {
	  *((string*)ti->var) = string(value);
	} else if (ti->type == kTString) {
	  *((TString*)ti->var) = (TString) value;
	} else {
	  Error("THcParmList","No conversion for strings: %s",key);
	}
      }
    }
    if (this_cnt<=0) {
      if ( !ti->optional ) {
        string msg = string("Could not find `") + key + "` in database!";
        throw std::runtime_error("<THcParmList::LoadParmValues>: " + msg);
      }
    }
    cnt += this_cnt;
    ti++;
  }
  return cnt;
}

//  READING AN ARRAY INTO A C-style ARRAY
//_____________________________________________________________________________
Int_t THcParmList::GetArray(const char* attr, Int_t* array, Int_t size)
{
  // Read in a set of Int_t's in to a C-style array.
  
  return ReadArray(attr,array,size);
}
//_____________________________________________________________________________
Int_t THcParmList::GetArray(const char* attr, Double_t* array, Int_t size)
{
  // Read in a set of Double_t's in to a vector.
  
  return ReadArray(attr,array,size);
}

//_____________________________________________________________________________
template<class T>
Int_t THcParmList::ReadArray(const char* attrC, T* array, Int_t size)
{
  // Copy values from parameter store to array
  // No resizing is done, so only 'size' elements may be stored.

  Int_t cnt=0;

  THaVar *var = Find(attrC);
  if(!var) return(cnt);
  VarType ty = var->GetType();
  if( ty != kInt && ty != kDouble) {
    cout << "*** ERROR: " << attrC << " has unsupported type " << ty << endl;
    return(cnt);
  }
  Int_t sz = var->GetLen();
  const void *vp = var->GetValuePointer();
  if(size != sz) {
    cout << "*** WARNING: requested " << size << " elements of " << attrC <<
      " which has length " << sz << endl;
  }
  if(size<sz) sz = size;
  Int_t donint = 0;
  if(ty == kDouble && typeid(array[0]) == typeid(Int_t)) {
    donint = 1;			// Use nint when putting doubles in nint
    cout << "*** WARNING!!!  Rounded " << attrC << " elements to nearest integer " << endl;
  }
  for(cnt=0;cnt<sz;cnt++) {
    if(ty == kInt) {
      array[cnt] = ((Int_t*)vp)[cnt];
    } else
      if(donint) {
	array[cnt] = TMath::Nint(((Double_t*)vp)[cnt]);
      } else {
	array[cnt] = ((Double_t*)vp)[cnt];
      }
  }
  return(cnt);
}

//_____________________________________________________________________________
void THcParmList::PrintFull( Option_t* option ) const
{
  // Print all the numeric parameter desciptions and values.
  // Print all the text parameters
  THaVarList::PrintFull(option);
  TextList->Print();
}
#ifdef WITH_CCDB
//_____________________________________________________________________________
Int_t THcParmList::OpenCCDB(Int_t runnum)
{
  // Use the Environment variable "CCDB_CONNECTION" as the
  // connection string
  const char* connection_string = gSystem->Getenv("CCDB_CONNECTION");

  return(OpenCCDB(runnum,connection_string));
}
Int_t THcParmList::OpenCCDB(Int_t runnum, const char* connection_string)
{
  // Connect to a CCDB database pointed to by connection_string

  std::string s (connection_string);
  CCDB_obj = new SQLiteCalibration(runnum);
  Int_t result = CCDB_obj->Connect(s);
  if(!result) return -1;	// Need some error codes
  cout << "Opened " << s << " for run " << runnum << endl;
  return 0;
}
Int_t THcParmList::CloseCCDB()
{
  delete CCDB_obj;
  return(0);
}
Int_t THcParmList::LoadCCDBDirectory(const char* directory, 
				     const char* prefix)
{
  // Load all parameters in directory
  // Prepend prefix onto the name of each

  std::string dirname (directory);

  if(dirname[dirname.length()-1]!='/') {
    dirname.append("/");
  }
  Int_t dirlen=dirname.length();

  vector<string> namepaths;
  CCDB_obj->GetListOfNamepaths(namepaths);
  for(UInt_t iname=0;iname<namepaths.size();iname++) {
    std::string varname (namepaths[iname]);
    if(varname.compare(0,dirlen,dirname) == 0) {
      varname.replace(0,dirlen,prefix);
      //      cout << namepaths[iname] << " -> " << varname << endl;

      // To what extent is there duplication here with Load() method?

      // Retrieve assignment
      Assignment* assignment = CCDB_obj->GetAssignment(namepaths[iname], true);
      ConstantsTypeColumn::ColumnTypes ccdbtype=assignment->GetValueType(0);
      Int_t ccdbncolumns=assignment->GetColumnsCount();
      Int_t ccdbnrows=assignment->GetRowsCount();
      std::string title = assignment->GetTypeTable()->GetComment();

      // Only load single column tables
      if(ccdbncolumns == 1) {

	THaVar* existingvar=Find(varname.c_str());
	// Need to append [size] to end of varname
	char sizestring[20];
	sprintf(sizestring,"[%d]",ccdbnrows);
	std::string size_str (sizestring);
	std::string varnamearray (varname);
	varnamearray.append(size_str);

	// Select data type
	if(ccdbtype==ConstantsTypeColumn::cIntColumn) {
	  vector<vector<int> > data;
	  CCDB_obj->GetCalib(data, namepaths[iname]);

	  if(existingvar) {
	    RemoveName(varname.c_str());
	  }

	  Int_t* ip = new Int_t[data.size()];
	  for(UInt_t row=0;row<data.size(); row++) {
	    ip[row] = data[row][0];
	  }
	  Define(varnamearray.c_str(), title.c_str(), *ip);

	} else if (ccdbtype==ConstantsTypeColumn::cDoubleColumn) {
	  vector<vector<double> > data;
	  CCDB_obj->GetCalib(data, namepaths[iname]);

	  if(existingvar) {
	    RemoveName(varname.c_str());
	  }

	  Double_t* fp = new Double_t[data.size()];
	  for(UInt_t row=0;row<data.size(); row++) {
	    fp[row] = data[row][0];
	  }
	  Define(varnamearray.c_str(), title.c_str(), *fp);
	} else if (ccdbtype==ConstantsTypeColumn::cStringColumn) {
	  if(ccdbnrows > 1) {
	    cout << namepaths[iname] << ": Only first element of CCDB string array loaded."  << endl;
	  }
	  vector<vector<string> > data;
	  CCDB_obj->GetCalib(data, namepaths[iname]);
	  AddString(varname, data[0][0]);
	} else {
	  cout << namepaths[iname] << ": Unsupported CCDB data type: " << ccdbtype << endl;
	}
      } else {
	cout << namepaths[iname] << ": Multicolumn CCDB variables not supported" << endl;
      }
    }	
  }
  return 0;
}

#endif