case

问题 I was working is this simple exercise about writing certified function using subset types. The idea is to first write a predecessor function pred : forall (n : {n : nat | n > 0}), {m : nat | S m = n.1}. and then using this definition give a funtion pred2 : forall (n : {n : nat | n > 1}), {m : nat | S (S m) = n.1}. I have no problem with the first one. Here is my code Program Definition pred (n : {n : nat | n > 0}) : {m : nat | S m = n.1} := match n with | O => _ | S n' => n' end. Next

问题 I was working is this simple exercise about writing certified function using subset types. The idea is to first write a predecessor function pred : forall (n : {n : nat | n > 0}), {m : nat | S m = n.1}. and then using this definition give a funtion pred2 : forall (n : {n : nat | n > 1}), {m : nat | S (S m) = n.1}. I have no problem with the first one. Here is my code Program Definition pred (n : {n : nat | n > 0}) : {m : nat | S m = n.1} := match n with | O => _ | S n' => n' end. Next

问题 Could you tell my why the following isnt working in postgres sql?: See updated code below UPDATE: I expect the query to return "0.30" as float. This construct is only for testing purposes, i have some complex querys which depend on this conditional structure... BUt i dont know how to fix it.. Result is: ERROR: syntax error at or near "1" LINE 4: if 1=1 then UPDATE: This construction appears in a function... so I want to do following: CREATE FUNCTION f_test(myvalue integer) RETURNS float AS $$

问题 (case [dbo].[YearsInService]([DateEngaged],getdate()) when (0) then (0) when (1) then (4) when (2) then (8) when (3) then (12) when (4) then (32) when (5) then (40) when (6) then (48) when (7) then (56) when (8) then (104) when (9) then (117) when (10) then (150) else (-1) end) Now in my the last line, how can i say that 10 and above should be returned as 150? 回答1: You can't, the CASE YourFunction WHEN ... is for equalities only. If you need to use "greater than", you'll need to rewrite your

问题 Although I have come up with a work-around using multiple if / else if statements, I am curious in knowing what looks wrong with my case statements, illustrated below: function [ar_vo,bucket] = revEng(v) ... s=solve(solve>0) * sqrt(T); ar_vo=s; bucket=ri(ar_vo); %%%%%%%%%%%%%%%%%%%%% function bucket = ri(ar_vo) % switch(ar_vo) % case ((ar_vo >= 0)&&(ar_vo < 0.005)) (1) % bucket=1; % case ((ar_vo >= 0.005)&&(ar_vo < 0.02)) (2) % bucket=2; % case ((ar_vo >= 0.02)&&(ar_vo < 0.05)) (3) % bucket=3

问题 im learning how to use the SELECT CASE but i don't understand very well, here is the code: SET @vgls=1; SET @lgls=1; SET @st=SELECT CASE WHEN @vgls=@lgls THEN "emp" WHEN @vgls>@lgls THEN "loc" WHEN @vgls<@lgls THEN "vis" END; SELECT @st; It gives me the following error: [Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to you MySQL server version for the right syntax to use near 'SELECT CASE WHEN @vgls=@lgls THEN "emp" WHEN @vgls>@lgls THEN "loc" WHEN @vg'

问题 Why is it not possible to use enum values as strings in a switch case? (Or what is wrong with this:) String argument; switch (argument) { case MyEnum.VALUE1.toString(): // Isn't this equal to "VALUE1" ? // something break; case MyEnum.VALUE2.toString(): // something else break; 回答1: You can only use strings which are known at compile time. The compiler cannot determine the result of that expression. Perhaps you can try String argument = ... switch(MyEnum.valueOf(argument)) { case VALUE1: case

问题 I am trying to retrieve a value for a alias column using case statement. CASE WHEN FieldA = 'TestA' THEN FieldA1 WHEN FieldB = 'TestB' THEN FieldB1 ELSE NULL END AS Alias1 But when I try to use this alias to retrievce value for another alias , I am getting an error CASE WHEN Alias1 = FieldA1 THEN FieldA0 WHEN Alias1 = FieldB1 THEN FieldA1 ELSE NULL END AS Alias2 Error message I get is : Can you suggest a way to get rid of the error or any alternative approach which fulfills my requirements

问题 final int a = 1; final int b; b = 2; final int x = 0; switch (x) { case a:break; // ok case b:break; // compiler error: Constant expression required } /* COMPILER RESULT: constant expression required case b:break; ^ 1 error */ Why am I getting this sort of error? If I would have done final int b = 2 , everything works. 回答1: b may not have been initialized and it is possible to be assigned multiple values. In your example it is obviously initialized, but probably the compiler doesn't get to

问题 I have a SELECT statement being calculated from a CASE WHEN THEN state (or could use multiple IF statements) aliased as 'Length', and I need to correctly GROUP the results together. The SELECT seems to be working, but the group groups them wrong. Here is my statement: SELECT CASE WHEN DATEDIFF(o.EndDate, o.StartDate) < 30 THEN '<1 Month' WHEN DATEDIFF(o.EndDate, o.StartDate) < 90 THEN '1 - 2 Months' WHEN DATEDIFF(o.EndDate, o.StartDate) < 210 THEN '3 - 4 Months' ELSE '>4 Months' END AS