What is the output of the Java program?
int a=10;
if(a==9)
System.out.println("OK ");
System.out.println("MASTER");
else
System.out.println("BYE");
It gives you error
$javac HelloWorld.java
HelloWorld.java:12: error: 'else' without 'if'
else
^
1 error
You can put braces like
int a=10;
if(a==9){
System.out.println("OK ");
System.out.println("MASTER");
}
else
System.out.println("BYE");
To get output
BYE
Related
Imagine I have some function like this:
fun dummyFunction():Int{
if(True){
val a = 1
} else {
val a = 2
}
return a
}
Stack trace (from LeetCode):
Line 7: Char 11: error: unresolved reference: a
return a
^
Why this code gives unresolved reference: a error? Every help is appreciated
P.S. I know how to solve this. But I got curious about this very situation
This error is for scope of variables
The "a" variable just exist in {} of the if and the else
Way to fix this problem is define the "a" in out of if-else
Don't hate cause of Turbo, I already hate my school!
I wish to show an error msg if a character is entered instead of an int or float in some file such as age or percentage.
I wrote this function:
template <class Type>
Type modcin(Type var) {
take_input: //Label
int count = 0;
cin>>var;
if(!cin){
cin.clear();
cin.ignore();
for ( ; count < 1; count++) { //Printed only once
cout<<"\n Invalid input! Try again: ";
}
goto take_input;
}
return var;
}
but the output is not desirable:
How do I stop the error msg from being repeated multiple times?
Is there a better method?
NOTE: Please make sure that this is TurboC++ that we are talking about, I tried using the approach in this question, but even after including limits.h, it doesn't work.
Here, a code snippet in C++.
template <class Type>
Type modcin(Type var) {
int i=0;
do{
cin>>var;
int count = 0;
if(!cin) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
for ( ; count < 1; count++) { //Printed only once
cout<<"\n Invalid input! Try again: ";
cin>>var;
}
}
} while (!cin);
return var;
}
The variables are tailored to match yours' so you can understand better. This code isn't perfect though.
It can't handle cases like "1fff", here you would just get a 1 in return. I tried solving it but then a infinite loop was being encountered, when I'll fix it, I'll update the code.
It also can't function in TurboC++ effectively. I don't know if there are alternatives but the numeric_limits<streamsize>::max() argument gives a compiler error ('undefined symbol' error for numeric_limits & streamsize and 'prototype must be defined' error for max()) in Turbo C++.
So, to make it work in Turbo C++. Replace the numeric_limits<streamsize>::max() argument with some big int value such as 100.
This will make it so that the buffer is only ignored/cleared till 100 characters are reached or '\n' (enter button/newline character) is pressed.
EDIT
The following code can be executed on both Turbo C++ or proper C++. The comments are provided to explain the functioning:
template <class Type> //Data Integrity Maintenance Function
Type modcin(Type var) { //for data types: int, float, double
cin >> var;
if (cin) { //Extracted an int, but it is unknown if more input exists
//---- The following code covers cases: 12sfds** -----//
char c;
if (cin.get(c)) { // Or: cin >> c, depending on how you want to handle whitespace.
cin.putback(c); //More input exists.
if (c != '\n') { // Doesn't work if you use cin >> c above.
cout << "\nType Error!\t Try Again: ";
cin.clear(); //Clears the error state of cin stream
cin.ignore(100, '\n'); //NOTE: Buffer Flushed <|>
var = modcin(var); //Recursive Repeatation
}
}
}
else { //In case, some unexpected operation occurs [Covers cases: abc**]
cout << "\nType Error!\t Try Again: ";
cin.clear(); //Clears the error state of cin stream
cin.ignore(100, '\n'); //NOTE: Buffer Flushed <|>
var = modcin(var);
}
return var;
//NOTE: The '**' represent any values from ASCII. Decimal, characters, numbers, etc.
}
I'm very new to ANTLR4 and am trying to build my own language. So my grammar starts at
program: <EOF> | statement | functionDef | statement program | functionDef program;
and my statement is
statement: selectionStatement | compoundStatement | ...;
and
selectionStatement
: If LeftParen expression RightParen compoundStatement (Else compoundStatement)?
| Switch LeftParen expression RightParen compoundStatement
;
compoundStatement
: LeftBrace statement* RightBrace;
Now the problem is, that when I test a piece of code against selectionStatement or statement it passes the test, but when I test it against program it fails to recognize. Can anyone help me on this? Thank you very much
edit: the code I use to test is the following:
if (x == 2) {}
It passes the test against selectionStatement and statement but fails at program. It appears that program only accepts if...else
if (x == 2) {} else {}
Edit 2:
The error message I received was
<unknown>: Incorrect error: no viable alternative at input 'if(x==2){}'
Cannot answer your question given the incomplete information provided: the statement rule is partial and the compoundStatement rule is missing.
Nonetheless, there are two techniques you should be using to answer this kind of question yourself (in addition to unit tests).
First, ensure that the lexer is working as expected. This answer shows how to dump the token stream directly.
Second, use a custom ErrorListener to provide a meaningful/detailed description of its parse path to every encountered error. An example:
public class JavaErrorListener extends BaseErrorListener {
public int lastError = -1;
#Override
public void syntaxError(Recognizer<?, ?> recognizer, Object offendingSymbol, int line, int charPositionInLine,
String msg, RecognitionException e) {
Parser parser = (Parser) recognizer;
String name = parser.getSourceName();
TokenStream tokens = parser.getInputStream();
Token offSymbol = (Token) offendingSymbol;
int thisError = offSymbol.getTokenIndex();
if (offSymbol.getType() == -1 && thisError == tokens.size() - 1) {
Log.debug(this, name + ": Incorrect error: " + msg);
return;
}
String offSymName = JavaLexer.VOCABULARY.getSymbolicName(offSymbol.getType());
List<String> stack = parser.getRuleInvocationStack();
// Collections.reverse(stack);
Log.error(this, name);
Log.error(this, "Rule stack: " + stack);
Log.error(this, "At line " + line + ":" + charPositionInLine + " at " + offSymName + ": " + msg);
if (thisError > lastError + 10) {
lastError = thisError - 10;
}
for (int idx = lastError + 1; idx <= thisError; idx++) {
Token token = tokens.get(idx);
if (token.getChannel() != Token.HIDDEN_CHANNEL) Log.error(this, token.toString());
}
lastError = thisError;
}
}
Note: adjust the Log statements to whatever logging package you are using.
Finally, Antlr doesn't do 'weird' things - just things that you don't understand.
Here's the ugly long code:
var i;
if(true)
i = 1;
else
i = 0;
When I try this:
var i = (true ? 0 : 1);
it doesn't work resulting in an error on the following line. I guess I was a bit inattentive reading Dart's syntax specs, so can anybody show me the right way?
This looks perfectly fine from a syntax point of view. You can omit the parentheses.
I get a warning 'Dead code' at '1' with your example because of 'true'.
The Darteditor shows you a hint that you wrote code that may contain a bug because he knows your expression can never evaluate to 1 because of the hardcoded 'true'.
void main(List<String> args) {
var b = true;
var i = b ? 0 : 1;
}
doesn't produce a warning.
#include<stdio.h>
#include<error.h>
#include<sys/shm.h>
#include "/opt/PostgreSQL/9.1/include/libpq-fe.h"
int main()
{
PGconn *conn;
int buf_ptr=0;
int i;
{
fprintf(stderr,"connection to database failed:%s",PQerrorMessage(conn));
exit(0);
}
else
{
printf("connection to database successful \n");
}
printf("Do you want to create a table enter 1 \n ");
scanf("%d",&i);
if(i==1)
{
EXEC SQl CREATE TABLE EMPOYE(
ENO INT,
ENAME VARCHAR(10));
}
return 0;
}
hello i am a newbie i am learning embedded c
i want to create a simple code where a table is created in c
when i am compiling the above program i am getting error like
embc.c:25: error: âEXECâ undeclared (first use in this function)
embc.c:25: error: (Each undeclared identifier is reported only once
embc.c:25: error: for each function it appears in.)
embc.c:25: error: expected â;â before âSQlâ
please help
First, the connection to database is missing, you should have something like :
int i=0;
EXEC SQL CONNECT TO target [AS connection-name] [USER user-name];
Or
PGconn *conn;
int buf_ptr=0;
int i=0;
conn = PQconnectdbParams(const char **keywords, const char **values, int expand_dbname);
then save your source file as prog.pgc and run :
ecpg prog.pgc
this will create a file called prog.c which can be compiled as a standard C file.