Re: Get point is moving backwards.
RyanMcCoskrie wrote:
This is an oversimplified version that does nothing much but will
give the same effect:
int main(int argc, char **argv)
{
ifstream input(argv[1]);
string str;
while(input >> str){
if(str == "foo") foo();
}
}
void foo()
{
string str;
if(input >> str) cout << str;
else exit(1);
}
I don't think that the code above will compile and show whatever problem
you have in mind.
In this example there are to words in the input file: bar and baz.
The bug comes up on the second iteration of the loop in main, for some
reason the program here is reading from the beginning of the file but
the foo function reads it from the correct position and thus exits the
program with an error.
I'm not sure I understand what that means.
I rewrote your code to make a few small changes. I changed the call to
exit to throw an exception instead and added try/catch. I passed input
to foo, so that the symbol is defined and uses the same stream as main
uses. I put the code in a little loop, so that I could try it with
different "files" although I used a std::istringstream instead of a
std::ifstream, it just seemed like it would be a little easier for
testing, although there is the possibility of a bug in your version of
std::ifstream that doesn't exist in std::istringstream. The example
below is complete and compilable although perhaps not commendable.
#include <iostream>
#include <sstream>
#include <string>
struct FooException {};
void foo(std::istream &input) {
std::string str;
if(input >> str) {
std::cout << str << std::endl;
}
else {
throw FooException();
}
}
void test(const std::string &text) {
try {
std::istringstream input(text);
std::string str;
while(input >> str) {
if(str == "foo") {
foo(input);
}
}
}
catch( const FooException &) {
std::cout << "FooException caught" << std::endl;
}
catch(...) {
std::cout << "exception caught" << std::endl;
}
}
int main() {
static const std::string tests[] = {
"bar baz",
"bar foo",
"bar foo baz",
};
for(size_t i=0; i<sizeof(tests)/sizeof(tests[0]); i++) {
const std::string &t = tests[i];
std::cout
<< "** "
<< unsigned int(i)
<< " trying "
<< t
<< std::endl;
test(t);
}
}
The output from this is:
** 0 trying bar baz
** 1 trying bar foo
FooException caught
** 2 trying bar foo baz
baz
This seems to make sense to me, so I think that I don't understand
exactly what problem you're having. If the above doesn't work the same
way for you, or if it doesn't shed light on the problem you're having,
could you please post a small example that compiles on your system and
demonstrates the actual problem that you're having and could you please
say what compiler and version you're using.
Thanks,
LR
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