[solved] Parsing expressions in xml file

abich

hello,
I use QRegExp to parse my expression.
@QString expression = "len>=1";

QRegExp xp("(\\w+)"); 
QString clockname, op, ter;


if (xp.indexIn(expression) != -1)
{
     clockname = xp.cap(1); // clockname=len
     op=xp.cap(2);// op is empty
     ter=xp.cap(3);//ter is empty

}@

My problem is that I can get clockname content but for the other variables i have nothing: they are empty.
I think my QRegExp is wrong, can any one help me?

MementoMori

having the text "len>=1" what do you want inside clockname, op and ter variables ?

Xander84

Hi, first if you are using Qt 5+ you should use QRegularExpression instead of QRegExp. QRegularExpression is easier to use, more standard compliant to the pear regex syntax and also faster (I think).

Ok about your regex string, it would help to know how your input can look like, maybe provide some more examples instead of just one? What I see you are just trying to use a "string split" with "\w" that is just word character (letters, numbers and _ as far as I know).
Also you are using the "indexIn" method, I don't hink that is what you want, you should check the introduction and examples in the documentation first: http://qt-project.org/doc/qt-5/qregularexpression.html#details

abich

using the expression "len>=1" i want to have "len" inside clockname, ">=" inside op and "1" inside ter.

PS: i have Qt 4

Xander84

ok then you have to stick with QRegExp for now..
anyway we don't know much about what the values in your case can be, that is why i asked for more examples.
With your single example it should be pretty easy if you have a "string" followed by a comparison or something and followed by a number.

you could use a regex like "(\w+)(\W+)(\d+)" maybe?

abich

In fact i have several values such as:
"x>=5 && y==0"
"x>=5 || y==0"
"x==5"
"e=id,x=0"

Xander84

well if you have AND (&&) and OR (||) relations and other stuff it might be a little more complicated, because you will have everything twice (variable, operator and value)?
I was playing around a little this code might be helpful to you:
@
QString expression = "x>=5 && y==0";

QRegExp xp(R"((\w+)(\W+)(\d+)\s*(&&|||)?)"); // c++11 raw string
QString clockname, op, ter, con;
int pos = 0;

while ((pos = xp.indexIn(expression, pos)) != -1)
{
clockname = xp.cap(1);
op = xp.cap(2);
ter = xp.cap(3);
con = xp.cap(4); // optional
pos += xp.matchedLength();
qDebug() << clockname << op << ter << con;
}
@
output for this example:
@
"x" ">=" "5" "&&"
"y" "==" "0" ""
@
if you can't use c++11 raw string you have to escape the regex (use \ for every )...

abich

it doesn't work unfortunately :/
What's c++ 11 raw ?? i used the expression with \, it is not working too

abich

the expression i used was:
@QRegExp xp("((\w+)(\W+)(\d+)\s*(\&\&|\|\|)?)");@

output:
@"x>=5&&" "x" ">=" "5"
"y==0" "y" "==" "0"@

Xander84

yeah sorry for the confusion with the raw string...

a raw string looks like this
@
R"(string)" == "string"
@
the () are part of the string delemiter and not the string content I think that confused you, so to convert my raw string you have to omit the outer ():
@
QRegExp xp(R"((\w+)(\W+)(\d+)\s*(&&|||)?)"); // c++11 raw string
// same as
QRegExp xp("(\w+)(\W+)(\d+)\s*(\&\&|\|\|)?"); // escaped string
@
if you leave the outer "( )" that is obviously the first regex capture ground and not want you wanted I guess. :)

If you want to learn more about c++11 string literals take a look at this site for example: http://en.cppreference.com/w/cpp/language/string_literal

abich

thanks for your help, it works! :)