i was messing around with eval, but stumbled across this error:
VM153:1 Uncaught SyntaxError: Unexpected token ':'
at :2:1
the code is:
var gridSize = 20;
eval("{'x': gridSize, 'y':gridSize}")
what is happening here???
I was expecting the vm to compile it, since if you remove the quotation marks around the expression it works
eval() takes a statement sequence. So something like eval('{x: 10}') will be syntatically correct, but does not do anything. It is a block consisting of a labeled statement.
If you do eval("({'x': 10})"), that will return an object with a x property.
It's not common to use eval though! Also, interestingly, eval returns the value of the last expression statement...
Related
I'm asking this question after asking that one. We experience a line break problem with the for each (...in...) statement in C++/CLI formating.
My question is quite simple: in C++/CLI, are for each two tokens for the tokenizer or a single one with a space (0x20) inside it?
My point is that I tought that no token could contain a space but when they are split (by clang-format formatter) in two lines like this:
for
each ( auto a in b )
{
}
I get the errors:
C2061 syntax error: identifier 'each'
C2143 syntax error: missing ';' before '{'
But when I write:
for each ( a in aa ) {}
I have no error.
I want to take the modulus of a value when using Impala and I am aware of the abs() function. When I use this however like such
select abs(value) from table
It returns a value that is rounded to the nearest integer. The documentation found here states that I need to define the numeric_type. have tried this
select abs(float value) from table
but this gives me the following error
AnalysisException: Syntax error in line 1: ... abs(float value) from table ^ Encountered: FLOAT Expected: ALL, CASE, CAST, DEFAULT, DISTINCT, EXISTS, FALSE, IF, INTERVAL, NOT, NULL, TRUNCATE, TRUE, IDENTIFIER CAUSED BY: Exception: Syntax error
Any ideas how I set abs() to return a float?
This should work SELECT cast(Abs(-243.5) as float) AS AbsNum
I think you are misunderstanding the syntax. You call the function as abs(val). The return type is the same as the input type. It should work on integers, decimals, and floats.
If you want a particular type being returned, then you need to pass in that type, perhaps casting to the specific type.
The documentation is:
abs(numeric_type a)
Purpose: Returns the absolute value of the argument.
Return type: Same as the input value
Admittedly, this does look like the type should be part of the function call. But it is really using a programming language-style declaration to show the types that are expected.
If the input to a grako/tatsu generated parser has a syntax error, such as 3 + / 3 to the calc.py examples, one gets a long list of Python calling sequences in addition to the relevant
3 + / 3
^
I could use try - except constructions but then I lose the relevant part of the error message as well.
I would like to use grako/tatsu to parse grammar rules for a rule compiler and I appreciate the possibility of separating the syntax and semantics in a clean way. The users would be quite annoyed of the excessive error messages. Is there a way for clean error messages?
This should be the same as in any Python program. If you let the exception escape main(), then a stack trace will be printed. Instead, you can write:
try:
do_parse()
except Exception as e:
print(str(e))
I have a user defined CLR aggregate function that can potentially throw an error. I would like to know how to handle an error if one occurs in my query.
The function is performing an IRR calculation similar to that which Excel does, ie. an iterative root-finding calculation. If no root is found, an error is thrown. This is the error I need to handle.
The query is part of a larger stored procedure and it looks something like:
select
MyID,
Excel_XIRR(col1)
from #t
group by MyID
and the error i get is something like this:
A .NET Framework error occurred during execution of user-defined routine or aggregate "Excel_Xirr":
System.ArgumentException: Not found an interval comprising the root after 60 tries, last tried was (-172638549748481000000000.000000, 280537643341281000000000.000000)
System.ArgumentException:
at System.Numeric.Common.rfindBounds#59(FastFunc`2 f, Double minBound, Double maxBound, Double precision, Double low, Double up, Int32 tries)
at System.Numeric.Common.findBounds(FastFunc`2 f, Double guess, Double minBound, Double maxBound, Double precision)
at System.Numeric.Common.findRoot(FastFunc`2 f, Double guess)
at Excel_Xirr.Terminate()
My problem is that not all the rows cause this error. There are some legitimate results from the query that I want to capture and use later in my stored procedure. Will this error stop me from getting the results of the query? If so, is there a way to figure out which rows throw the error (dynamically) and then rerun the query for the rest of the rows?
Not sure how well you have coded the XIRR function itself, looking at your function prototypes in Error messages it would seem you are using a Bi-section method of finding roots which is not most suitable to algorithms to use when it comes to finding rates. You will be locking yourself within a lower and upper bound no matter how large this bound is it is not going to help for all cases
As for solving your immediate problem with handling the error, you can change your .net code and replace the Throw...Exception statement with a return value of Math.Pow(-1, 0.5)
This will return a NAN to the calling program which you can then check with an IF statement to confirm whether your XIRR value is a number (when IRR is found) or a NAN value (when IRR is not found)
I have a simple grammar that works for the most part, but at one place it reports error and I think it shouldn't, because it can be resolved using backtracking.
Here is the portion that is problematic.
command: object message_chain;
object: ID;
message_chain: unary_message_chain keyword_message?
| binary_message_chain keyword_message?
| keyword_message;
unary_message_chain: unary_message+;
binary_message_chain: binary_message+;
unary_message: ID;
binary_message: BINARY_OPERATOR object;
keyword_message: (ID ':' object)+;
This is simplified version, object is more complex (it can be result of other command, raw value and so on, but that part works fine). Problem is in message_chain, in first alternative. For input like obj unary1 unary2 it works fine, but for intput like obj unary1 unary2 keyword1:obj2 is trys to match keyword1 as unary message and fails when it reaches :. I would think that it this situation parser would backtrack and figure that there is : and recognize that that is keyword message.
If I make keyword message non-optional it works fine, but I need keyword message to be optional.
Parser finds keyword message if it is in second alternative (binary_message) and third alternative (just keyword_message). So something like this gives good results: 1 + 2 + 3 Keyword1:Value
What am I missing? Backtracking is set to true in options and it works fine in other cases in the same grammar.
Thanks.
This is not really a case for PEG-style backtracking, because upon failure that returns to decision points in uncompleted derivations only. For input obj unary1 unary2 keyword1:obj2, with a single token lookahead, keyword1 could be consumed by unary_message_chain. The failure may not occur before keyword_message, and next to be tried would be the second alternative of message_chain, i.e. binary_message_chain, thus missing the correct parse.
However as this grammar is LL(2), it should be possible to extend lookahead to avoid consuming keyword1 from within unary_message_chain. Have you tried explicitly setting k=2, without backtracking?