I'm trying to do the aggregate insertion of x-monotone polylines, but I get the following error:
terminate called after throwing an instance of 'CGAL::Precondition_exception'
what(): CGAL ERROR: precondition violation!
Expr: i != INVALID_INDEX
File: /home/vladimir/lib-cgal/include/CGAL/Arr_polycurve_basic_traits_2.h
Line: 727
And have no clue why it happens. Do I miss something? Is my input wrong? Or is it a bug? Here is a code snippet resulting in this behavior:
#include <vector>
#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Arr_segment_traits_2.h>
#include <CGAL/Arr_polyline_traits_2.h>
#include <CGAL/Arrangement_2.h>
typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef Kernel::Point_2 Point_2;
typedef CGAL::Arr_segment_traits_2<Kernel> Segment_traits_2;
typedef CGAL::Arr_polyline_traits_2<Segment_traits_2> Geom_traits_2;
typedef CGAL::Arrangement_2<Geom_traits_2> Arrangement_2;
int main()
{
Arrangement_2 arr;
std::vector<Geom_traits_2::X_monotone_curve_2> segments;
{
auto ctor = arr.geometry_traits()->construct_x_monotone_curve_2_object();
typedef std::vector<Point_2> Line;
std::vector<Line> lines = {
{{0,0}, {8,0}},
{{2,0}, {7,0}},
{{4,2}, {6,3}},
{{1,1}, {3,0}, {5,0}},
};
for (auto &line: lines) {
segments.push_back(ctor(line.begin(), line.end()));
}
}
insert(arr, segments.begin(), segments.end());
return 0;
}
CGAL version I'm using is 4.7, but I have tried it with 4.5.2 and the lates git version (81d638341) with the same result.
The lines are intersecting, but that should be fine as I understand. I have observed that changing {{1,1}, {3,0}, {5,0}} to {{2,1}, {3,0}, {5,0}} results in no error. And splitting {{1,1}, {3,0}, {5,0}} into two segments {{1,1}, {3,0}}, {{3,0}, {5,0}} results in no error as well.
I have also noticed another thread (link) with similar problem which was fixed, but I don't see this fix in the version 4.7. Probably it's fixed somewhere else in the code, or perhaps this fix got lost somehow.? Anyway, it looks like it's not related to my problem, but one never knows.
I was able to reproduce the problem and at first glance it looks like a bug. We are looking into it, but for now you have 2 options to work around the problem:
1. Use incremental insertion. The incremental insertion is based on a completely different algorithm.
2. Break each polyline into segments and construct an arrangement of segments instead of an arrangement of polylines. I've tested it with the minimal example that produces the problem you provided (that you, by the way for that) and it works fine.
BW, the link you mentioned is unrelated.
Related
Using this https://github.com/antlr/grammars-v4/tree/master/cpp antlr grammar Im trying to parse C++ code. Below is the same visitor class I'm using, I don't have much visitor function implemented,
#include <iostream>
#include <antlr4-runtime.h>
#include "parser/CPP14Lexer.h"
#include "parser/CPP14BaseVisitor.h"
#include "parser/CPP14Parser.h"
#include "parser/CPP14Visitor.h"
class TREEVisitor : public CPP14BaseVisitor {
public:
virtual antlrcpp::Any TREEVisitor::visitAdditiveExpression(
CPP14Parser::AdditiveExpressionContext *ctx) override
{
std::cout << "AddExpr : " << ctx->getText() << std::endl;
std::vector<CPP14Parser::MultiplicativeExpressionContext *> mulpExprCtx =
ctx->multiplicativeExpression();
for (CPP14Parser::MultiplicativeExpressionContext *mulpExprLp : mulpExprCtx)
{
std::vector<CPP14Parser::PointerMemberExpressionContext *> ptrMbrExprCtx =
mulpExprLp->pointerMemberExpression();
// ptrMbrExprCtx->pointerMemberExpression()->castExpression()->unaryExpression();
// Different parts of an expression
for (CPP14Parser::PointerMemberExpressionContext *ptrMbrExprLp : ptrMbrExprCtx)
{
std::cout << "=> " << ptrMbrExprLp->getText() << std::endl;
}
}
return visitChildren(ctx);
}
};
int main(int argc, char *argv[]) {
std::ifstream stream;
stream.open(argv[1]);
antlr4::ANTLRInputStream input(stream);
CPP14Lexer lexer(&input);
antlr4::CommonTokenStream tokens(&lexer);
CPP14Parser parser(&tokens);
antlr4::tree::ParseTree *tree = parser.translationunit();
// Visitor
auto *visitor = new TREEVisitor();
visitor->visit(tree);
return 0;
}
Im trying to parse the following C++ code,
int ii = a + b - getLength() * 10 / 1;
What I'm trying to achieve here is to get all of the variables that are used to initilize the variable i and their signs. Something like below, where i can relate each sign to the values/variables(for example to know that + as after a.
a
+
b
-
getLength()
*
10
/
1;
So far I can only get an output as follow,
AddExpr : a+b-c*10/1
=> a
=> b
=> getLength()
=> 10
=> 1
I don't seem to be able to get the signs between each operation.
I seem to have something related to the signs in that equation, I had only Star and Mod.
tree::TerminalNode* startTn = mulpExprLp->Star();
So I tried to change the grammar file to get other signs as well. While that gave me the signs in that equation but again... I wasn't ablel to know the position of each sign in the equation.
multiplicativeExpression:
pointerMemberExpression (
(Star | Div | Mod | Plus | Minus) pointerMemberExpression
)*;
I hope I could describe the problem clearly. I basically want to read the each part of an equation and know what is the position of each sign.
Thanks,
Alex
It looks like you need a better understanding of the structure of your parse tree.
I would suggest going back to the original grammar (there are many problems with your multiplcativeExpression, mostly around it not building a proper parse tree.
Viewing the graphical version of your parse tree should be quite useful. This page gives a brief intro to setting up a grun alias to use TestRig. It’s usually a good idea to “play around” a bit with grun and various input to gain a better understanding of what ANTLR produces (token streams, parse trees, etc.) for your grammar.
Take a look at the documentation and how to run the TestRig utility with the -gui command line option. This will give you a graphical representation of your parse tree. Your immediate issue is that, since you only have a visitor for additiveExpression, it won’t include the sub tree for the mutiplicativeExpression that will hold the structure for multiplication and division.
Also, since you’re not finding the operations you need to take a closer look at the cpp14parser::AdditiveExpressionContext generated for your additiveExpression. The operator(s) should be available at one of the indices of your children nodes (the rule is written to allow multiple addition/subtraction in a single context, so they’ll probably be available in some list/array structure (sorry, not intimately familiar with what ANTLR generates for C++)
BTW, you may find that, for your purposes, a listener is easier to use than a visitor. With Listeners a ParseTreeWalker takes care of walking the tree and calling back to your code as nodes are encountered. With Visitors, it’s up to you to navigate the parse Tree (they can be useful when you need more flexibility, and a bit easier to handle things if you want a value returned from visiting a node, but I find Listeners much simpler for most use cases)
So I tried using code from another post around here to see if I could use it, it was a code meant to utilize a potentiometer to move a servo motor, but when I attempted to compile it is gave the error above saying No operator "=" matches these operands in "Servo_Project.cpp". How do I go about fixing this error?
Just in case ill say this, the boards I was trying to compile the code were a NUCLEO-L476RG, the board from the post I mentioned utilized Nucleo L496ZG board and a Tower Pro Micro Servo 9G.
#include "mbed.h"
#include "Servo.h"
Servo myservo(D6);
AnalogOut MyPot(A0);
int main() {
float PotReading;
PotReading = MyPot.read();
while(1) {
for(int i=0; i<100; i++) {
myservo = (i/100);
wait(0.01);
}
}
}
This line:
myservo = (i/100);
Is wrong in a couple of ways. First, i/100 will always be zero - integer division truncates in C++. Second, there's not an = operator that allows an integer value to be assigned to a Servo object. YOu need to invoke some kind of Servo method instead, likely write().
myservo.write(SOMETHING);
The SOMETHING should be the position or speed of the servo you're trying to get working. See the Servo class reference for an explanation. Your code tries to use fractions from 0-1 and thatvisn't going to work - the Servo wants a position/speed between 0 and 180.
You should look in the Servo.h header to see what member functions and operators are implemented.
Assuming what you are using is this, it does have:
Servo& operator= (float percent);
Although note that the parameter is float and you are passing an int (the parameter is also in the range 0.0 to 1.0 - so not "percent" as its name suggests - so be wary, both the documentation and the naming are poor). You should have:
myservo = i/100.0f;
However, even though i / 100 would produce zero for all i in the loop, that does not explain the error, since an implicit cast should be possible - even if clearly undesirable. You should look in the actual header you are using to see if the operator= is declared - possibly you have the wrong file or a different version or just an entirely different implementation that happens to use teh same name.
I also notice that if you look in the header, there is no documentation mark-up for this function and the Servo& operator= (Servo& rhs); member is not documented at all - hence the confusing automatically generated "Shorthand for the write and read functions." on the Servo doc page when the function shown is only one of those things. It is possible it has been removed from your version.
Given that the documentation is incomplete and that the operator= looks like an after thought, the simplest solution is to use the read() / write() members directly in any case. Or implement your own Servo class - it appears to be only a thin wrapper/facade of the PwmOut class in any case. Since that is actually part of mbed rather than user contributed code of unknown quality, you may be on firmer ground.
I'm using the CGAL library in a a Visual Studio project.
I'm trying to create a polygon_set_2 composed of polygons with holes. I run into an exception when creating the polygon_set_2 even when just using simple polygons.
Typedefs:
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef K::Point_2 CGALPoint;
typedef CGAL::Polygon_2<K> CGALInnerPolygon;
typedef CGAL::Polygon_set_2<K> CGALMultiPolygon;
Problem code:
CGALInnerPolygon cgalpoly;
cgalpoly.push_back(CGALPoint(0, 0));
cgalpoly.push_back(CGALPoint(1, 1));
cgalpoly.push_back(CGALPoint(1, 0));
CGALMultiPolygon multipolygon;
multipolygon.insert(cgalpoly);
I get an exception on the insert call. Output for the exception is:
Exception thrown at 0x75112CF2 in XXX.exe: Microsoft C++ exception: CGAL::Precondition_exception at memory location 0x00191AF0
It was actually a combination of two things. First the polygon points much be counterclockwise as sloriot mentioned. To fix for this in the general case the following code was added:
if (cgalpoly.is_clockwise_oriented())
{
cgalpoly.reverse_orientation();
}
Secondly, the the Polygon_set_2 must use an exact construction kernel:
typedef CGAL::Exact_predicates_exact_constructions_kernel K;
I'm trying to do some 3D boolean operations with CGAL. I have successfully converted my polyhedra to nef polyhedra. However, when ever I try doing a simple union, I get an assertion fail on line 286 of SM_overlayer.h:
CGAL error: assertion violation!
Expression : G.mark(v1,0)==G.mark(v2,0)&& G.mark(v1,1)==G.mark(v2,1)
File : ./CGAL/include/CGAL/Nef_S2/SM_overlayer.h
Line : 287
I tried searching the documentation for "mark". Apparently it is a template argument on the Nef_polyhedron_3" that defaults to bool. However the documentation also says it is not implemented and that you shouldn't mess with it. I am a bit confused why there is even an assertion on some unimplemented feature. I tried simply commenting out the assertion, but it simply goes on to fail at a later point.
I am using the following kernel and typedefs as it was the only example I could find that allowed doubles in the construction of the meshes.
typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef CGAL::Nef_polyhedron_3<Kernel> Nef_polyhedron;
typedef CGAL::Polyhedron_3<Kernel> Polyhedron;
I used CGAL 4.6.3 installed with the exe installer. I have also tried the 4.7 beta and I get the same exception(at line 300 instead though).
Related github issue: https://github.com/CGAL/cgal/issues/353
EDIT: The issue turned out to be with the meshes. The meshes I were using had self intersections. Thus, even though is_valid, is_closed and is_triangular returned true, the mesh was in valid for conversion to a nef polyhedron. From CGAL 4.7. The Polygon mesh processing package has been introduced which contains this which can be used to check for self intersections.
I have a simple c program for printing n Fibonacci numbers and I would like to compile it to ELF object file. Instead of setting the number of fibonacci numbers (n) directly in my c code, I would like to set them in the registers since I am simulating it for an ARM processor.How can I do that?
Here is the code snippet
#include <stdio.h>
#include <stdlib.h>
#define ITERATIONS 3
static float fib(float i) {
return (i>1) ? fib(i-1) + fib(i-2) : i;
}
int main(int argc, char **argv) {
float i;
printf("starting...\n");
for(i=0; i<ITERATIONS; i++) {
printf("fib(%f) = %f\n", i, fib(i));
}
printf("finishing...\n");
return 0;
}
I would like to set the ITERATIONS counter in my Registers rather than in the code.
Thanks in advance
The register keyword can be used to suggest to the compiler that it uses a registers for the iterator and the number of iterations:
register float i;
register int numIterations = ITERATIONS;
but that will not help much. First of all, the compiler may or may not use your suggestion. Next, values will still need to be placed on the stack for the call to fib(), and, finally, depending on what functions you call within your loop, code in the procedure are calling could save your register contents in the stack frame at procedure entry, and restore them as part of the code implementing the procedure return.
If you really need to make every instruction count, then you will need to write machine code (using an assembly language). That way, you have direct control over your register usage. Assembly language programming is not for the faint of heart. Assembly language development is several times slower than using higher level languages, your risk of inserting bugs is greater, and they are much more difficult to track down. High level languages were developed for a reason, and the C language was developed to help write Unix. The minicomputers that ran the first Unix systems were extremely slow, but the reason C was used instead of assembly was that even then, it was more important to have code that took less time to code, had fewer bugs, and was easier to debug than assembler.
If you want to try this, here are the answers to a previous question on stackoverflow about resources for ARM programming that might be helpful.
One tactic you might take is to isolate your performance-critical code into a procedure, write the procedure in C, the capture the generated assembly language representation. Then rewrite the assembler to be more efficient. Test thoroughly, and get at least one other set of eyeballs to look the resulting code over.
Good Luck!
Make ITERATIONS a variable rather than a literal constant, then you can set its value directly in your debugger/simulator's watch or locals window just before the loop executes.
Alternatively as it appears you have stdio support, why not just accept the value via console input?