if-statement

问题 I am trying to check that a string contains only / and digits, to use as a form of validation, however I cannot find and way to do both. ATM I have this: if Variable.isdigit() == False: This works for the digits but I have not found a way to check also for the slashes. 回答1: There are many options, as showed here. A nice one would be list comprehensions. Let's consider two strings, one that satisfies the criteria, other that doesn't: >>> match = "123/456/" >>> no_match = "123a456/" We can

问题 I am trying to check that a string contains only / and digits, to use as a form of validation, however I cannot find and way to do both. ATM I have this: if Variable.isdigit() == False: This works for the digits but I have not found a way to check also for the slashes. 回答1: There are many options, as showed here. A nice one would be list comprehensions. Let's consider two strings, one that satisfies the criteria, other that doesn't: >>> match = "123/456/" >>> no_match = "123a456/" We can

问题 In JAGS I'd like to define a Poisson distribution for parameter w[i] which is also truncated (greater than or equal to 2) if another parameter, e[i], is greater than 0. Essentially I want it to represent: w[i] ~ ifelse( e[i] > 0, dpois(mu) T(2,) , dpois(mu) ) I've tried using the step function by adapting the code that was given in response to someone else's post which was requesting something similar: Choosing Different Distributions based on if - else condition in WinBugs/JAGS But this

问题 Using Sql Server 2012. I have a stored procedure and part of it checks if a username is in a table. If it is, return a 1, if not, return a 2. This is my code: IF EXISTS (SELECT * FROM tblGLUserAccess WHERE GLUserName ='xxxxxxxx') 1 else 2 However, I keep receiving the below error: Incorrect syntax near '1'. Is this even possible with an IF EXIST? Regards, Michael 回答1: If you want to do it this way then this is the syntax you're after; IF EXISTS (SELECT * FROM tblGLUserAccess WHERE GLUserName

问题 Please consider these piece of C code: if ((value & 1) == 1) { } Assuming value equals 1, will (value & 1) return 1 or any unspecified non zero number? 回答1: §6.5.8 Relational operators Each of the operators < (less than), > (greater than), <= (less than or equal to), and >= (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.) The result has type int. §6.5.9 Equality operators The == (equal to) and != (not equal to) operators are analogous to the

问题 if ((vnd = (struct diam_vnd_t *)g_hash_table_lookup(vendors,vend))) {...} Can you tell me why it is an assignment but not a boolean expression in the brackets ? And in what situation this assignment can be considered "true" or "false" ? 回答1: Quoting C11 , chapter §6.5.16, Assignment operators ( emphasis mine ) An assignment operator stores a value in the object designated by the left operand. An assignment expression has the value of the left operand after the assignment, 111) but is not an

问题 if ((vnd = (struct diam_vnd_t *)g_hash_table_lookup(vendors,vend))) {...} Can you tell me why it is an assignment but not a boolean expression in the brackets ? And in what situation this assignment can be considered "true" or "false" ? 回答1: Quoting C11 , chapter §6.5.16, Assignment operators ( emphasis mine ) An assignment operator stores a value in the object designated by the left operand. An assignment expression has the value of the left operand after the assignment, 111) but is not an

问题 I am using && like this and it works typeof foo === 'function' && foo(); //if foo exist then call it instead of if (typeof foo === 'function') { foo(); } Is it wrong to do or just a matter of style and taste? For me it is natural and I want to use && , but now a linter complained: Expected an assignment or function call and instead saw an expression. Can there be any real issues here or is it just a matter of convention? Here is a code snippet: function foo(x) { console.log("foo say " + x) }

问题 I am using && like this and it works typeof foo === 'function' && foo(); //if foo exist then call it instead of if (typeof foo === 'function') { foo(); } Is it wrong to do or just a matter of style and taste? For me it is natural and I want to use && , but now a linter complained: Expected an assignment or function call and instead saw an expression. Can there be any real issues here or is it just a matter of convention? Here is a code snippet: function foo(x) { console.log("foo say " + x) }

问题 I have this code: bool value = false; if(value) { Console.Write("true"); } else { Console.Write("false"); } and I want to shorten it by using the conditional operator but I can't find the correct syntax. bool value = false; value ? Console.Write("true") : Console.Write("false"); // does not work 回答1: Put the operator inside Console.Write Console.Write(value ? "true" : "false"); or if you really want to write the value: Console.Write(value); if you want to call 2 different Methods, you can