logical-operators

Logical Operators and increment operators [duplicate]

由 我的梦境 提交于 2019-12-04 07:15:34
问题 This question already has an answer here : Short circuit behavior of logical expressions in C in this example (1 answer) Closed last year . Can anyone explain this code? How value is assigned to only variable m but the output is for all variables change. Also the roles of logical operator and increment operators over here. #include <stdio.h> #include <stdlib.h> int main() { int i=-3, j=2, k=0, m; m = ++i || ++j && ++k; printf("%d%d%d%d\n", i, j, k, m); return 0; } 回答1: || or logical OR

Why is the statement using relation operators evaluate to 1 in the following code?

由 北城余情 提交于 2019-12-04 07:14:35
问题 Shouldn't the value of i be 0? Since x #include<stdio.h> int main(void) { int x = 10,y=20,z=5,i; i=x<y<z; printf("%d",i); return 0; } 回答1: In your code, due to the LTR associativity of the relational operators, i=x<y<z; evaluates to i=(x<y)<z; which is i=(10<20)<z; which is i= 1 < 5; which is TRUE (1). That 1 gets stored in i . That's it. 来源： https://stackoverflow.com/questions/34481683/why-is-the-statement-using-relation-operators-evaluate-to-1-in-the-following-cod

Why is {} < function(){}?

由 爷，独闯天下 提交于 2019-12-04 06:10:50
While I was messing around with truth tables in JavaScript, I noticed that the following evaluates to true: var a, b, c; a = {}; b = function(){}; c = a < b; console.log(c); Why? I've only tested this in Firefox, and I'm sure I could dig up the details in the ECMAScript 2.6.2 spec, but TBH I'm feeling lazy. JavaScript type coercion makes the comparison essentially String({}) < String(function(){}) so essentially you are just doing "[object Object]" < "function (){}" which is a lexicographic string comparison. SLaks Javascript compares objects by calling valueOf() or toString() . Since neither

Slicing with a logical (boolean) expression a Pandas Dataframe

由 一笑奈何 提交于 2019-12-04 04:26:26
问题 I am getting an exception as I try to slice with a logical expression my Pandas dataframe. My data have the following form: df GDP_norm SP500_Index_deflated_norm Year 1980 2.121190 0.769400 1981 2.176224 0.843933 1982 2.134638 0.700833 1983 2.233525 0.829402 1984 2.395658 0.923654 1985 2.497204 0.922986 1986 2.584896 1.09770 df.info() <class 'pandas.core.frame.DataFrame'> Int64Index: 38 entries, 1980 to 2017 Data columns (total 2 columns): GDP_norm 38 non-null float64 SP500_Index_deflated

Why do logical operators in C not evaluate the entire expression when it's not necessary to?

由 痴心易碎 提交于 2019-12-04 04:03:34
问题 I was reading my textbook for my computer architecture class and I came across this statement. A second important distinction between the logical operators ' && ' and ' || ' versus their bit-level counterparts ' & ' and ' | ' is that the logical operators do not evaluate their second argument if the result of the expression can be determined by evaluating the first argument. Thus, for example, the expression a && 5/a will never cause a division by zero, and the expression p && *p++ will never

Can the C compiler optimizer violate short-circuiting and reorder memory accesses for operands in a logical-AND expression?

由 痞子三分冷 提交于 2019-12-04 03:27:50
问题 We know that logical-AND operator ( && ) guarantees left-to-right evaluation. But I am wondering if the compiler optimizer can ever reorder the memory access instructions for *a and b->foo in the following code, i.e. the optimizer writes instructions that try to access *b before accessing *a . (Consider both a and b to be pointers to memory regions in the heap.) if (*a && b->foo) { /* do something */ } One might think that && causes a sequence point, so the compiler must emit instructions to

Does short circuiting make execution of the program faster, and is analysing which statement to put first in the condition statement worth it? [closed]

由 独自空忆成欢 提交于 2019-12-04 03:15:43
Closed . This question is opinion-based. It is not currently accepting answers. Learn more . Want to improve this question? Update the question so it can be answered with facts and citations by editing this post . Closed 3 years ago . For instance (Lets say we are talking about C++ if that makes a differnce), In an && operator if I know that one statement will result to 0 more often/has a higher chance then the other statement should I put that on the left side, and the other statement on the right? Same goes for || operator if I know that one statement will result to 1 more often/has a higher

MongoDB in Go (golang) with mgo: how to use logical operators to query?

由 喜欢而已 提交于 2019-12-04 03:04:39
I would like to run the following query in golang using mgo in a pipeline. {"key1" : 1, "$or" : [{"key2" : 2}, {"key3" : 2}]} I have looked everywhere, but I cannot find an example like this. I have tried many different combinations, for example: ... pipeline := []bson.M{ bson.M{ "$match" : bson.M{ "key1" : 1, "$or" : bson.M{ "key2" : 2, "key3" : 2}, } ... } which compiles correctly, does not find anything. Any ideas? Thank you in advance Your mongo query can be translated to the following: pipeline := bson.D{ {"key1", 1}, {"$or", []interface{}{ bson.D{{"key2", 2}}, bson.D{{"key3", 2}}, }}, }

Checking the “boolean” result of an “int” type

由 风流意气都作罢 提交于 2019-12-04 02:43:01
问题 I'm learning Java, coming from C and I found an interesting difference between languages with the boolean type. In C there is no bool / ean so we need to use numeric types to represent boolean logic ( 0 == false ). I guess in Java that doesn't work: int i = 1; if (i) System.out.println("i is true"); Nor does changing the conditional via a typecast: if ((boolean)i) So besides doing something like: if ( i != 0 ) Is there any other way to do a C-ish logic check on an int type? Just wondering if

PHP FizzBuzz Logic

由 别说谁变了你拦得住时间么 提交于 2019-12-04 02:09:36
问题 When we write the fizzbuzz script, why are we testing to see if it is equal to 0? Or am I misunderstanding? Example: $i % 3 == 0 <?php for ($i=1; $i<=100; $i++) { if ($i%3==0 && $i%5==0) { echo 'FizzBuzz'; }else if($i%3==0){ echo 'Fizz'; }else if($i%5==0){ echo 'Buzz'; }else{ echo $i; } echo "\n"; } 回答1: The program fizzbuzz prints 'fizz' if a number is divisible by 3, 'buzz' if a number is divisible by 5, and 'fizzbuzz' if a number is divisible by both. Your program is not checking if the
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