does anybody know how to get struct from line? For example, i have struct:
struct Variable {
Variable(){}
string m_name = "";
uint_16 value = 0;
string comments = "";
}
And some variants of line:
string line = "foo 0x22 #Comments"; //hex value
or
string line = "foo 222 #Comments"; //decimal value
or
string line = "foo ((1<4)&2) #Comments"; //expression value
or
string line = "foo ((1<4)&2)"; //without comment
The question is, should i use syntax analysis? Thanks.
Assuming all your fields are separated by a common delimiter (And that I've understood your question correctly), just break up the input string at the delimiters and consume them with string conversion functions. something like:
Variable parseVariable(const std::string& line)
{
Variable variable;
// You must define 'split'
std::vector<std::string> inputFields = split(line, " ");
variable.m_name = inputFields[0];
// You must also define 'convertStringToUint16'
variable.value = convertStringToUint16(inputFields[1]);
if(inputFields.size() > 2)
{
variable.comments = inputFields[2];
}
return variable;
}
Disclaimer: this code has not been tested
Now, regarding your use of the term "expression" I am worried that you may want to be able to evaluate arbitrary expressions for the value variable. If so, I recommend you define a VERY small scope of expressions that can be evaluated, as even simple mathematical expressions require decent work to process correctly.
Related
An input file is entered with the following data:
Juan Dela Cruz 150.50 5
'Juan Dela Cruz' is a name that I would like to assign to string A,
'150.50' is a number I would like to assign to float B
and 5 is a number I would like to assign to int C.
If I try cin, it is delimited by the spaces in between.
If I use getline, it's getting the whole line as a string.
What would be the correct syntax for this?
If we analyze the string, then we can make the following observation. At the very end, we have an integer. In front of the integer we have a space. And in front of that the float value. And again in fron of that a space.
So, we can simply look from the back of the string for the 2nd last space. This can easily be achieved by
size_t position = lineFromeFile.rfind(' ', lineFromeFile.rfind(' ')-1);
We need a nested statement of rfind please see here, version no 3.
Then we build a substring with the name. From start of the string up to the found position.
For the numbers, we put the rest of the original string into an std::istringstream and then simply extract from there.
Please see the following simple code, which has just a few lines of code.
#include <iostream>
#include <string>
#include <cctype>
#include <sstream>
int main() {
// This is the string that we read via getline or whatever
std::string lineFromeFile("Juan Dela Cruz 150.50 5");
// Let's search for the 2nd last space
size_t position = lineFromeFile.rfind(' ', lineFromeFile.rfind(' ')-1);
// Get the name as a substring from the original string
std::string name = lineFromeFile.substr(0, position);
// Put the numbers in a istringstream for better extraction
std::istringstream iss(lineFromeFile.substr(position));
// Get the rest of the values
float fValue;
int iValue;
iss >> fValue >> iValue;
// Show result to use
std::cout << "\nName:\t" << name << "\nFloat:\t" << fValue << "\nInt:\t" << iValue << '\n';
return 0;
}
Probably simplest in this case would be to read whole line into string and then parse it with regex:
const std::regex reg("\\s*(\\S.*)\\s+(\\d+(\\.\\d+)?)\\s+(\\d+)\\s*");
std::smatch match;
if (std::regex_match( input, match, reg)) {
auto A = match[1];
auto B = std::stof( match[2] );
auto C = std::stoi( match[4] );
} else {
// error invalid format
}
Live example
As always when the input does not (or sometimes does not) match a strict enough syntax, read the whole line and then apply the rules which to a human are "obvious".
In this case (quoting comment by john):
Read the whole string as a single line. Then analyze the string to work out where the breaks are between A, B and C. Then convert each part to the type you require.
Specifically, you probably want to use reverse searching functions (e.g. https://en.cppreference.com/w/cpp/string/byte/strrchr ), because the last parts of the input seem the most strictly formatted, i.e. easiest to parse. The rest is then the unpredictable part at the start.
either try inputting the different data type in different lines and then use line breaks to input different data types or use the distinction to differentiate different data types like adding a . or comma
use the same symbol after each data package, for example, Juan Dela Cruz;150.50;5 then you can check for a ; and separate your string there.
If you want to use the same input format you could use digits as an indicator to separate them
How can i replace multiple occurrences of a character with a string containing the occurrence number.
e.g if i have the following expression.
insert into emp values(?,?,?)
I want the following converted string.
insert into emp values(_p_1,_p_2,_p_3)
I am trying this using the boost regular expression.
Can anyone tell me how to achieve this using the boost c++ (with no or minimum iteration).
currently I am using the following approach:
std::wstring q=L"insert into emp values(?,?,?)";
auto loc = q.find(L"?");
auto len = wcslen(L"?");
auto c=1;
while(loc != std::wstring::npos)
{
q.replace(loc, len , L"_p_"+to_wstring(c));
c++;
loc = q.find(L"?");
}
cout<<q.c_str();
Please suggest better and efficient approaches.
I'd just forget regular expressions and trying to do this simple thing with Boost.
It's like asking, "how do I add 1 to a variable using Boost regular expressions"?
Best answer, IMHO, is to instead just use ++ for the task of adding 1, and to use a loop to replace special characters with strings.
string const query_format = "insert into emp values(?,?,?)";
string const params[] = {"_p_1", "_p_2", "_p3"};
string query;
string const* p = params;
for( char const c : query_format )
{
if( c == '?' ) { query += *p++; } else { query += c; }
}
// Use `query`
One might choose to wrap this up as a replace function.
Disclaimer: code not touched by compiler.
If you control the query_format string, why not instead make the placeholders compatible with Boost format.
Re the parenthetical requirement
” with no or minimum iteration
there's iteration involved no matter how you do this. You can hide the iteration behind a function name, but that's all. It's logically impossible to actually avoid the iteration, and it's trivial (completely trivial) to hide it behind a function name.
I'm trying to read a ini file in a value listbox.
Example below works, but i don't know why.
ReadSectionValues contains a string list of ini lines.
How does Rad Studio parse the lines with:
ListValues->Names[i] is first part of the line and ListValues->Values[ListValues->Names[i]] is the second part?
int i;
try
{
//ShowMessage( ListBox1->Items->Strings[ListBox1->ItemIndex] );
TStringList *ListValues = new TStringList;
TIniFile* SettingsFile = new TIniFile(ExtractFilePath(Application->ExeName) + "settings.ini");
String s;
s = ListBox1->Items->Strings[ListBox1->ItemIndex];
SettingsFile->ReadSectionValues( s , ListValues);
for (i = 0; i < (ListValues->Count); i++) {
//ShowMessage(ListValues->Names[i]);
//ShowMessage(ListValues->Values[ListValues->Names[i]]);
vList1->InsertRow(ListValues->Names[i] , ListValues->Values[ListValues->Names[i]],True);
}
delete SettingsFile;
delete ListValues;
}
catch(Exception* e)
{
ShowMessage(e->Message);
}
Please explain, Rad stuido help found no explanation.
void __fastcall ReadSectionValues(
const System::UnicodeString Section,
System::Classes::TStrings* Strings
)
is a method, which gets all lines of ini-file section with name Section and stores them in TStrings-object Strings. Note that these strings have format name=value.
TStrings class has two access properties Names and Values. Their parse algorithm is very simple. If you get stringsObject->Values[1] it takes second line from stringsObject and splits it into two strings on = (or other value of NameValueSeparator property of stringsObject). The string to the left of = (separator) is returned as name (by property Name) and the string to the right of = is returned as value (by property Value).
I have two vectors, one which holds my regular expressions and one which holds the string in which will be checked against the regular expression, most of them work fine except for this one (shown below) the string is a correct string and matches the regular expression but it outputs incorrect instead of correct.
INPUT STRING
.C/IATA
CODE IS BELOW
std::string errorMessages [6][6] = {
{
"Correct Corparate Name\n",
},
{
"Incorrect Format for Corporate Name\n",
}
};
std::vector<std::string> el;
split(el,message,boost::is_any_of("\n"));
std::string a = ("");
for(int i = 0; i < el.size(); i++)
{
if(el[i].substr(0,3) == ".C/")
{
DCS_LOG_DEBUG("--------------- Validating .C/ ---------------");
output.push_back("\n--------------- Validating .C/ ---------------\n");
str = el[i].substr(3);
split(st,str,boost::is_any_of("/"));
for (int split_id = 0 ; split_id < splitMask.size() ; split_id++ )
{
boost::regex const string_matcher_id(splitMask[split_id]);
if(boost::regex_match(st[split_id],string_matcher_id))
{
a = errorMessages[0][split_id];
DCS_LOG_DEBUG("" << a )
}
else
{
a = errorMessages[1][split_id];
DCS_LOG_DEBUG("" << a)
}
output.push_back(a);
}
}
else
{
DCS_LOG_DEBUG("Do Nothing");
}
st[split_id] = "IATA"
splitMask[split_id] = "[a-zA-Z]{1,15}" <---
But it still outputs Incorrect format for corporate name
I cannot see why it prints incorrect when it should be correct can someone help me here please ?
Your regex and the surrounding logic is OK.
You need to extend your logging and to print the relevant part of splitMask and st right before the call to boost::regex_match to double check that the values are what you believe they are. Print them surrounded in some punctuation and also print the string length to be sure.
As you probably know, boost::regex_match only finds a match if the whole string is a match; therefore, if there is a non-printable character somewhere, or maybe a trailing space character, that will perfectly explain the result you have seen.
Ok, gah, syntax conversion issue here...How would I do this in AutoIt?
String theStr = "Here is a string";
String theNewStr = "";
for ( int theCount = 0; theCount < theStr.Size(); theCount++ )
{
theNewStr.Append(theStr[theCount]);
}
I am trying to access individual chars within a string in AutoIt and extract them. Thats's it. Thanks.
What about this:
$theStr = StringSplit("Here is a string", "") ; Create an array
$theNewStr = ""
For $i = 1 to $theStr[0] Step 1
$theNewStr = $theNewStr & $theStr[$i]
Next
MsgBox(0, "Result", $theNewStr)
#include <string>
std::string theStr = "Here is a string";
std::string theNewStr;
//don't need to assign blank string, already blank on create
for (size_t theCount = 0; theCount < theStr.Size(); theCount++ )
{
theNewStr += theStr[theCount];
}
//or you could just do
//theNewStr=theStr;
//instead of all the above
in autoit, it's just as simple to copy a string. to access a piece of a string (including a character, which is still a string) you use StringMid() which is a holdover from Microsoft BASIC-80 and now Visual BASIC (and all BASICs). you can stil do
theNewStr = theStr
or you can do it the hard way:
For $theCount = 1 to StringLen($theStr)
theNewStr &= StringMid($theStr, $theCount, 1)
Next
;Arrays and strings are 1-based (well arrays some of the time unfortunately).
& is concatenation in autoit. stringmid extracts a chunk of a string. it MIGHT also allow you to do the reverse: replace a chunk of a string with something else. but I would do unit testing with that. I think that works in BASIC, but not sure about autoit.