大约有 20,000 项符合查询结果（耗时：0.0442秒） [XML]
What is the difference between LL and LR parsing?
...ponds to Reverse Polish Notation. The difference between PN and RPN is the order of traversing the binary tree of the equation:
+ 1 * 2 3 // Polish (prefix) expression; pre-order traversal.
1 2 3 * + // Reverse Polish (postfix) expression; post-order traversal.
According to Haberman, this ill...
Finding duplicate rows in SQL Server
...CT
orgName, id,
ROW_NUMBER() OVER (PARTITION BY orgName ORDER BY id) AS intRow
FROM organizations
) AS d
WHERE intRow != 1
Edit: SQL Server 2000 doesn't have the ROW_NUMBER() function. Instead, you can use:
SELECT
o.id, o.orgName, d.intCount
FROM (
SELECT orgName,...
How to combine multiple conditions to subset a data-frame using “OR”?
... I intended, since ...
> NA & 1
[1] NA
> 0 & NA
[1] FALSE
Order of arguments may matter when using '&".
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How to select the rows with maximum values in each group with dplyr? [duplicate]
...g of A and B values.
group_by( A, B) %>%
# Sort rows in descending order by "value" column.
arrange( desc(value) ) %>%
# Pick the top 1 value
slice(1) %>%
# Remember to ungroup in case you want to do further work without grouping.
ungroup()
# Answering an extension of the ...
How to disable GCC warnings for a few lines of code
...
TL;DR: If it works, avoid, or use specifiers like __attribute__, otherwise _Pragma.
This is a short version of my blog article
Suppressing Warnings in GCC and Clang.
Consider the following Makefile
CPPFLAGS:=-std=c11 -W -Wall -pedantic -Werror
.PHONY: all
all: puts
fo...
How do I get the full path to a Perl script that is executing?
... if the script is at or below the CWD
Additionally, cwd(), getcwd() and abs_path() are provided by the Cwd module and tell you where the script is being run from
The module FindBin provides the $Bin & $RealBin variables that usually are the path to the executing script; this module also provides...
Is it possible to implement a Python for range loop without an iterator variable?
...ou can just live with the extra i variable.
Here is the option to use the _ variable, which in reality, is just another variable.
for _ in range(n):
do_something()
Note that _ is assigned the last result that returned in an interactive python session:
>>> 1+2
3
>>> _
3
F...
“Inner exception” (with traceback) in Python?
...peError("test")
except TypeError, e:
raise MyException(), None, sys.exc_info()[2]
Always do this when catching one exception and re-raising another.
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Format date and time in a Windows batch script
...== " " set day=0%day:~1,1%
echo day=%day%
set datetimef=%year%%month%%day%_%hour%%min%%secs%
echo datetimef=%datetimef%
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Best way to compare 2 XML documents in Java
...gify and compare. So regardless of whitespace irregularities or attribute ordering, you can get regular, predictable comparisons of your documents.
This works especially well in IDEs that have dedicated visual String comparators, like Eclipse. You get a visual representation of the semantic differ...