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I am new in programming but I have a yacc/lex project and some difficulty in writing the error message in detail (line and type of error). Any help with a small example, please.
Add the following to your flex scanner definition, to cause the scanner to track line numbers:
%option yylineno
(See the flex manual.)
Then add the following declarations to your bison grammar:
%define parse.error verbose
%define parse.lac full
(See the bison manual chapters on error reporting and LAC (lookahead correction).
Finally, use a definition of yyerror which uses the line number information. At a minimum, something like:
void yyerror(const char* msg) {
fprintf(stderr, "At line %d: %s\n", yylineno, msg);
}
Ask bad questions get correct but uninformative answers
void yyerror(const char *s);
extern int line_num;
void yyerror(const char *s)
{
std::cerr << "PARSING ERROR: " << line_num << " " << s << std::endl;
exit(1);
}
Related
this question is a continuing of Error on Constrained Delaunay Triangulation and Gabriel Triangulations
Trying to write a minimal example for that problem I planned insert the triangulation
in a file (std::ofstream) using the << operator of CDT without calling the CGAL::make_conforming_Delaunay_2(cdt); or CGAL::make_conforming_Gabriel_2(cdt),
knowing that until this point everything occured OK.
The triangulation was created without problems and before the exit of the aplication I saved the triangulation in a file using the << operator of CDT. The file was saved without error.
When I tried to read the file using the >> operator of CDT an exception was raised (inside the >> operator). The text of exception is:
CGAL ERROR: assertion violation!\nExpr: s == LEFT_TURN\nFile: C:\\dev\\CGAL-5.3.1\\include\\CGAL\\Triangulation_2.h\nLine: 919
The code I wrote:
int main()
{
CDT cdt;
std::ifstream ArqSuperficie("trian.dtr"); This file was created with << operator of CDT
if (ArqSuperficie.good() == false)
{
return 1;
}
try()
{
ArqSuperficie >> cdt;
}
catch(std::exception& e)
{
std::cerr << "ERROR: exception " << e.what() << std::endl;
}
return 0;
}
Why CDT cannot read a file created by itself, of a triangulation that was created by itself without errors?
Based on the message of the exception I can´t have a clue of what is happening...
Thank you
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I want to implement a command line application in C/Objective C which will act as a calculator of more than two numbers.
E.g ./calc 5 + 4 * 6
= 29
I just need an idea or simple algorithm to start. I will appreciate any help on this.
The algorithm you want is the infix notation to postfix notation converter.
You can find some more info on it over here.
http://scriptasylum.com/tutorials/infix_postfix/algorithms/infix-postfix/index.htm.
EDIT: I am not sure if this will help, but here is an implementation in Java. I'm not familiar with Objective-C
// converts a infix string to postfix string
private void convertInfixToPostfix(){
// create an empty operand stack
operatorStack = new Stack<>();
Operator operator = null;
Operand operand = null;
for(int i = 0; i < expressionTokens.size(); i++){
String token = expressionTokens.get(i);
Element element = new Element(token);
if(element.isOperand(token)){ // check if element is operand
// add the element to the postfix string
operand = new Operand(element.getStringValue());
postFixString.add(operand);
}
else if(operatorStack.isEmpty()){
// push the token to the operator stack, its an operator
operator = new Operator(element.getStringValue());
operatorStack.push(operator);
}
else {
operator = new Operator(element.getStringValue());
while(!operatorStack.isEmpty() &&
(operatorStack.peek().getPrecedence()
<= operator.getPrecedence()))
postFixString.add(operatorStack.pop());
operatorStack.push(operator);
}
}
// add the rest of the operator stack to the postfix string
while(!operatorStack.isEmpty()){
Operator remainingOperator = operatorStack.pop();
postFixString.add(remainingOperator);
}
}
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I have been assigned a project in my lab to implement CAN protocol on ARM 7.
I looked for some tutorials and sample code, but all looks so much complex that I think I should get some help on the coding part. Can anybody explain me the basic transmitter and receiver coding on any ARM board?
The sender code is the following. I have used question marks where I don't understand the full meaning of an expression.
#include <lpc23xx.h>
#include "type.h
#include "can.h"
#include <LPC23xx.H>
CAN_MSG MsgBuf_RX1,MsgBuf_RX2; // TX and RX Buffers for CAN message
volatile DWORD CAN1RxDone, CAN2RxDone;
int main(void)
{
DWORD tempbuf1,tempbuf2;
int current;
FIO2DIR=0x000000FF;
CAN_Init(BITRATE100K28_8MHZ);
MsgBuf_RX2.Frame = 0x0;
MsgBuf_RX2.MsgID = 0x0;
MsgBuf_RX2.DataA = 0x0;
MsgBuf_RX2.DataB = 0x0;
CAN_SetACCF(ACCF_BYPASS);
while (1)
{
while (!(CAN2GSR & (1 << 0)) )
;
if (CAN2RxDone == TRUE)
{
tempbuf1 = MsgBuf_RX2.DataA; // Data A has 32 bits, of which only the
// first 16 bits are actual data
tempbuf2 = (tempbuf1 & 0x0000ffff); //??
current = tempbuf2;
if ((current/3) >= 25)
FIO2SET |= 0x00000001; ///??
}
CAN2RxDone = FALSE;
if (MsgBuf_RX2.Frame & (1 << 10)) //?
{
MsgBuf_RX2.Frame &= ~(1 << 10); //?
}
}
}
Keil provides some examples and programs for CAN development: http://www.keil.com/dd/vtr/4152/7837.htm
Here you can find CAN source for LPC2129: http://www.siwawi.arubi.uni-kl.de/avr_projects/arm_projects/
Here some examples: http://mbed.org/handbook/CAN
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Closed 10 years ago.
I am new to TLM.
Someone can give me an example code for connecting two processes by a TLM fifo?
Thank you
I searched in doulos, but I only saw examples of sockets.
Someone helped me and I leave here a code example of a tlm fifo
#include "systemc"
#include "tlm.h"
// PRODUCER 1
SC_MODULE(producer)
{
sc_core::sc_port< tlm::tlm_fifo_put_if<int> > out; //FIFO OUT
SC_CTOR(producer)
: out("out")
{
SC_THREAD(run); //função
}
void run()
{
int i = 42;
std::cout << name() << ": " << i << std::endl;
out->put(i);
}
}; // producer
// CONSUMER
SC_MODULE(consumer)
{
sc_core::sc_port< tlm::tlm_fifo_get_if<int> > in;
SC_CTOR(consumer)
: in("in")
{
SC_THREAD(run); //função
}
void run()
{
int i = in->get();
std::cout << name() << ": " << i << std::endl;
}
}; // consumer
// MAIN
int sc_main(int, char*[] )
{
tlm::tlm_fifo<int> fifo("fifo");
producer prod("producer");
prod.out(fifo);
consumer cons("consumer");
cons.in(fifo);
sc_core::sc_start();
char myLine[100];
cin.getline(myLine, 100);
return 0;
}
Thank you
there are some good examples in doulos website.
I'm trying to allow users to simply hit Enter without typing anything, and use this to mean accepting a default value. scanf isn't doing what I want and the app still 'blocks': the next line of code doesn't run.
The only way is to actually type something THEN press Enter.
I tried using NSFileHandle and fileHandleWithStandardInput; however, it seems that the user is now forced to hit Ctrl-D to indicate EOF.
Someone suggested using fgets, but I cannot work out what to pass as 3rd parameter (of FILE* type). Tried stdin but it doesn't 'block'.
How do I accept input from a user, using Objective-C, and at the same time allow the user to simply hit Enter without being forced to type anything? How do I read a single line, even if that line is blank?
Assuming the code doesn't block and the next line runs immediately (as you seemed to indicate early in the question and in a comment), you have a common problem when mixing non-line-based and line-based input.
What happens is you have a newline left in the buffer, and fgets sees that, reads it, and returns, instead of doing what you really want: ignoring it, and then reading a line.
The solution is to simply do the ignoring part yourself, and then call fgets:
#include <stdio.h>
#include <string.h>
FILE* ignoreline(FILE* stream) {
for (int c; (c = fgetc(stream)) != EOF;) {
if (c == '\n') break;
}
return stream;
}
void example_use() {
char buf[1000];
ignoreline(stdin);
fgets(buf, sizeof buf, stdin);
// or, since it returns the stream, can be more compact:
fgets(buf, sizeof buf, ignoreline(stdin));
}
int main() { // error handling omitted
int n;
printf("Enter a number: ");
scanf("%d", &n);
char buf[1000];
printf("Enter a line: ");
ignoreline(stdin); // comment this line and compare the difference
fgets(buf, sizeof buf, stdin);
*strchr(buf, '\n') = '\0';
printf("You entered '%s'.\n", buf);
return 0;
}
Note that it is also common and encouraged to "pair" the ignoreline with the scanf (or other non-line-based input) to turn that into line-based input. You may want to modify it, in that case, so you can tell the difference between input of "42 abc" and "42" (in the "Enter a number" case). Some people just use fgets everywhere, then parse that line with sscanf, and while that works, it's not necessary.
I use getch(); in library conio.h
simply the program waits for any key to be pressed
If you're using Windows, you can use the ReadConsoleInput function (see MSDN for more on this) :
INPUT_RECORD keyin;
DWORD r;
while (ReadConsoleInput(GetStdHandle(STD_INPUT_HANDLE),&keyin,1,&r)) {
if (keyin.EventType!=KEY_EVENT) continue;
if (keyin.Event.KeyEvent.wVirtualKeyCode==VK_SPACE) break; ///use these VK codes to get any key's input
if (keyin.Event.KeyEvent.wVirtualKeyCode==VK_F1)
{
printf("You pressed F1\n");
}
if (keyin.Event.KeyEvent.wVirtualKeyCode==VK_F2)
{
printf("You pressed F2\n",);
}
}//end while loop
You don't need to hit enter after each key then.This works like a dream for me...
use getchar() to take input without using scanf function...