parentheses

问题 The command: ( echo 1 ) works fine when I input it in the command line but if I store it as a variable and call it, it gives the error: (echo: command not found Code: input="( echo 1 )" $input Why doesn't it evaluate the parentheses the same way and put it into a subshell when I call it this way? 回答1: This is discussed in full detail in BashFAQ #50. An unquoted expansion goes through only two stages of shell parsing: Field-splitting, and glob expansion. Thus, ( echo 1 ) is first split into

问题 I have this query implemented in two ways: SELECT race1, mode1 FROM organization WHERE condition = 1 LIMIT 1 UNION ALL (SELECT race2, mode2 FROM organization WHERE condition = 1 LIMIT 1) UNION ALL (SELECT race, mode FROM organization_new WHERE PK_Id = 1) And SELECT race1, mode1 FROM organization WHERE condition = 1 LIMIT 1 UNION ALL SELECT race2, mode2 FROM organization WHERE condition = 1 LIMIT 1 UNION ALL SELECT race, mode FROM organization_new WHERE PK_Id = 1 As you can see, the difference

问题 For example I have string: "one two (78-45ack sack); now (87 back sack) follow dollow (59 uhhaaa)" and I need only whole substring with parenthesis, containing word "back" , for this string it will be: "(87 back sack)" I've tried: (\(.*?back.*?\)) but it's return "(78-45ack sack); now (87 back sack)" How should my regex look like? As I understood it's happening cause search going from begin of the string, in common - how to perform regex to "search" from the middle of string, from the word

问题 I am having trouble implementing a function that given something like this: '((+(d + e) + f) + (a + (a + c)) Returns this: '(d + (e + (f + (a + (a + c))))) Now the catch is that I have to use associativity to get the answer so I only want to use this property: '((a + b) + c) = '(a + (b + c)) To get the correct output. I know how to implement the function for this case: '((a + b) + c) -> '(a + (b + c)) However I cannot seem to figure out how to implement it for the first case above (or any

问题 I'm trying to copy a file, >>> originalFile = '/Users/alvinspivey/Documents/workspace/Image_PCA/spectra_text/HIS/jean paul test 1 - Copy (2)/bean-1-aa.txt' >>> copyFile = os.system('cp '+originalFile+' '+NewTmpFile) But must first replace the spaces and parenthesis before the open function will work: /Users/alvinspivey/Documents/workspace/Image_PCA/spectra_text/HIS/jean\ paul\ test\ 1\ -\ Copy\ \(2\)/bean-1-aa.txt spaces ' ' --> '\ ' parenthesis '(' --> '\(' etc. Replacing the spaces work: >>

问题 I have a simple batch file that currently all it does it tries to connect to a wifi network up to 10 times. My trouble is that I am getting an unexpected output in my command prompt when it is ran. Here is my batch script setlocal EnableExtensions EnableDelayedExpansion echo. echo. :startSetVariables set timeout="2" set PINGS="4" set pingtimeout="1000" set endonfail="10" set wifissid="ROGAR Production" set /A COUNTER=1 :connectToTheInternet echo checking internet connection echo.

问题 I'm trying to use Parse::RecDescent make a parser which can parse parenthetical expressions and the unary operator ? . What I have so far is failing when I create the parser because the rule expression is left-recursive: use strict; use warnings; use Parse::RecDescent; my $test = <<END; ((foo)? bar) END my $grammar = q( parse: expression(s) expression: string | parend | expression(s) parend : "(" (string | expression) ")" /\??/ string : /\w+/ /\??/ ); my $parser = Parse::RecDescent->new(

问题 When I invoke a function with a space before the parens, it gives an error saying unepected , sum = (a, b) -> a+b console.log (sum (1, 2)) error: unexpected , console.log (sum (1, 2)) it points to the comma between 1 and 2 Why the odd behavior? 回答1: In CoffeeScript you can write function calls in two ways: foo(bar) # with parens foo bar # without parens Since you have a space between sum and (1, 2) , then you are making a unparenthesized functional call of sum passing (1, 2) as the first

问题 I was playing around with Swift today, and some strange types started to crop up: let flip = Int(random()%2) //or arc4random(), or rand(); whatever you prefer If I type flip into Xcode 6 (Beta 2), the auto-complete pops up, and says flip is of type (Int) instead of Int . This can easily be changed: let flip : Int = Int(random()%2) let flop = random()%2 Now flip and flop are of type Int instead of (Int) Playing around with it more, these "parentheses types" are predictable and you can cause

问题 Say I have func_a and func_b which both take one argument, and I want to pass the result of func_b to func_a . What is the most common way to parenthesize this? func_a func_b input func_a func_b(input) func_a(func_b input) func_a(func_b(input)) 回答1: You'd have to scan source to find the "most common". I try to write what makes sense under the circumstances, but would almost always use either: func_a func_b(arg) func_a(func_b(arg)) If the functions are named things that "sound like" a sentence