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/* xb_ex_expression.cpp
XBase64 Software Library
Copyright (c) 1997,2003,2014,2022 Gary A Kunkel
The xb64 software library is covered under
the terms of the GPL Version 3, 2007 license.
Email Contact:
xb64-devel@lists.sourceforge.net
xb64-users@lists.sourceforge.net
This example program demonstrates expression usage
*/
#include <xbase.h>
using namespace xb;
xbSchema MyV4Record[] =
{
{ "CFLD1", XB_CHAR_FLD, 20, 0 },
{ "CFLD2", XB_CHAR_FLD, 10, 0 },
{ "NFLD1", XB_NUMERIC_FLD, 5, 0 },
{ "DATE1", XB_DATE_FLD, 8, 0 },
{ "",0,0,0 }
};
//*********************************************************************************************************************************
void PrintResult( xbString *sExpression, xbExp *exp );
void PrintResult( xbString *sExpression, xbExp *exp ){
// Determine the expression return type
char cExpType = exp->GetReturnType();
// Process the expression results, dependent on return type
if( cExpType == XB_EXP_NUMERIC ){
xbDouble dResult;
exp->GetNumericResult( dResult );
std::cout << "Numeric result from expression [" << sExpression->Str() << "] is [" << dResult << "]" << std::endl;
} else if( cExpType == XB_EXP_DATE ){
xbDate dt;
exp->GetDateResult( dt );
std::cout << "Date result from expression [" << sExpression->Str() << "] is [" << dt.Str() << "]" << std::endl;
} else if( cExpType == XB_EXP_LOGICAL ){
xbBool bResult;
exp->GetBoolResult( bResult );
std::cout << "Bool result from expression [" << sExpression->Str() << "] is [" << (bResult ? " True" : "False") << "]" << std::endl;
} else if( cExpType == XB_EXP_CHAR ){
xbString sResult;
exp->GetStringResult( sResult );
std::cout << "Char result from expression [" << sExpression->Str() << "] is [" << sResult.Str() << "]" << std::endl;
}
}
//*********************************************************************************************************************************
int main( int ac, char ** av ){
xbInt16 iRc = 0;
xbInt16 iErrorStop = 0;
xbIx *pIx = NULL;
void *pTag = NULL;
xbXBase x;
xbDbf *MyFile = new xbDbf4( &x );
try{
if(( iRc = MyFile->CreateTable( "EXPEXAMPL.DBF", "TestMdxX2", MyV4Record, XB_OVERLAY, XB_MULTI_USER )) != XB_NO_ERROR ){
iErrorStop = 100;
throw iRc;
}
/*
CreateTag( const xbString &sIxType, const xbString &sName, const xbString &sKey, const xbString &sFilter,
xbInt16 iDescending, xbInt16 iUnique, xbInt16 iOverLay, xbIx **xbIxOut, void **vpTagOut );
*/
// the following index definition has two expressions
// 1) CFLD1+CFLD2 -- concat two char fields into an index key
// 2) .NOT. DELETED() -- don't include any deleted records in the index
if(( iRc = MyFile->CreateTag( "MDX", "TAG1", "CFLD1+CFLD2", ".NOT. DELETED()", 0, 0, XB_OVERLAY, &pIx, &pTag )) != XB_NO_ERROR ){
iErrorStop = 110;
throw iRc;
}
// add a record to the table
if(( iRc = MyFile->BlankRecord()) != XB_NO_ERROR ){
iErrorStop = 120;
throw iRc;
}
if(( iRc = MyFile->PutField( "CFLD1", "Some text" )) != XB_NO_ERROR ){
iErrorStop = 130;
throw iRc;
}
if(( iRc = MyFile->PutField( "CFLD2", "Other text" )) != XB_NO_ERROR ){
iErrorStop = 140;
throw iRc;
}
if(( iRc = MyFile->PutLongField( "NFLD1", 1000 )) != XB_NO_ERROR ){
iErrorStop = 150;
throw iRc;
}
xbDate dt;
dt.Set( "19890209" );
if(( iRc = MyFile->PutDateField( "DATE1", dt )) != XB_NO_ERROR ){
iErrorStop = 160;
throw iRc;
}
if(( iRc = MyFile->AppendRecord()) != XB_NO_ERROR ){
iErrorStop = 170;
throw iRc;
}
if(( iRc = MyFile->Commit()) != XB_NO_ERROR ){
iErrorStop = 180;
throw iRc;
}
// To use the XBase64 expression processing logic
// 1) Parse an expression with the xbExp::ParseExpression() method
// 2) Process the parsed expression with the xbExp::ProcessExpression() method
// 3) If needed, determine the expression return type with the xbExp::GetReturnType() method
// 4) Use the appriate methid to retrieve the expression value:
// xbExp::GetNumericResult()
// xbExp::GetDateResult()
// xbExp::GetLogicalResult()
// xbExp::GetStringResult()
// The expression only needs to be parsed once. The ProcessExpression() method can be used
// zero, one or many times after it is initially parsed.
// see docs/html/xbc5.html for expression documentation
// see example below
// Numeric expression example
xbString sExpression = "NFLD1 * (2 + RECNO())";
xbExp exp( &x );
// Parse the expression
if(( iRc = exp.ParseExpression( MyFile, sExpression )) != XB_NO_ERROR ){
iErrorStop = 190;
throw iRc;
}
// Process the parsed expression
if(( iRc = exp.ProcessExpression()) != XB_NO_ERROR ){
iErrorStop = 200;
return -1;
}
PrintResult( &sExpression, &exp );
// String expression example
sExpression = "CFLD1+CFLD2+'{'+DTOS(DATE1)+'}'";
xbExp exp2( &x );
if(( iRc = exp2.ParseExpression( MyFile, sExpression )) != XB_NO_ERROR ){
iErrorStop = 210;
throw iRc;
}
// Process the parsed expression
if(( iRc = exp2.ProcessExpression()) != XB_NO_ERROR ){
iErrorStop = 220;
return -1;
}
PrintResult( &sExpression, &exp2 );
// Date example
sExpression = "DATE() + 6";
xbExp exp3( &x );
if(( iRc = exp3.ParseExpression( MyFile, sExpression )) != XB_NO_ERROR ){
iErrorStop = 230;
throw iRc;
}
// Process the parsed expression
if(( iRc = exp3.ProcessExpression()) != XB_NO_ERROR ){
iErrorStop = 240;
return -1;
}
PrintResult( &sExpression, &exp3 );
// Logic example
sExpression = "NFLD1 = 5";
xbExp exp4( &x );
if(( iRc = exp4.ParseExpression( MyFile, sExpression )) != XB_NO_ERROR ){
iErrorStop = 250;
throw iRc;
}
// Process the parsed expression
if(( iRc = exp4.ProcessExpression()) != XB_NO_ERROR ){
iErrorStop = 260;
return -1;
}
PrintResult( &sExpression, &exp4 );
// Cleanup
MyFile->DeleteTable();
delete MyFile;
} catch (xbInt16 iRc ){
std::cout << "Error in program xb_ex_expression at location " << iErrorStop << std::endl;
std::cout << x.GetErrorMessage( iRc ) << std::endl;
}
return iRc;
}
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