NOTICE: pls this post is for experienced programmers only. if u don't understand what it means , just sit back and enjoy the explanation from our senior friends.

........AND if u know, please offer ur explanation. even if u are a newbie, u can benefit from this.


/************************************/
what is the difference between these two statements.

=================================

if(condition && condition){

}

----------------------------

if(condition){
if(condition){}
}

==================================

Whatching And ready to learn

pls all the programmers in the house should contribute for the benefit of all. it is very necessary

The way I see both conditions, they are different scenarios entirely... depending on the situation shaa

The first condition implies that if A and B are satisfied, do something. Else, do something else.

For instance, if my username is bruceleah and my password is xoxox, log me in into nairaland else prompt a mismatch.

The second condition is kinda different. It implies that if the first condition is satisfied, then check for the second condition and do something.

For instance, if my username is bruceleah, then check if my pasword xoxox. If true, log me into the programming section else if my password is yyy log me into the joke section.

Note that at both scenarios, the first condition is satisfied but the second is kinda handled differently

My opinion thoo.

Another scenario... Let's say we want to know if a username actually exist in our database, and check if the password matches the specified user name

The first example wld just throw a mismatch error

But the with d example, we could actually check if the username exists first, the throw an error if username does not exist. And den we check if the password matches the specified username. If not true, it throws a mismatch error.

No difference, they are both the same

Cybergenius:
No difference, they are both the same

Boss cybergenius, maybe you look at it from another point of view

bruceleah:
Another scenario... Let's say we want to know if a username actually exist in our database, and check if the password matches the specified user name

The first example wld just throw a mismatch error

But the with d example, we could actually check if the username exists first, the throw an error if username does not exist. And den we check if the password matches the specified username. If not true, it throws a mismatch error.

i love your assertion by bringing two use case illustrating each scenario perfectly. in fact if it was a competition i may likely give it to you . but lets keep this open for further thoughts and opinions.

There really is no difference between both as they are basically different ways to do the same thing which is check to make sure that two expressions in the condition are met before any code statement is executed. The first method is a more compact form.

Just like we have the while and for loop, both are used for the same thing but the for loop allows you to keep all your code expressions in one statement making it a more compact form.

An example.

if(9 > 7 && 7 < 9){
console.log('true');
}

Will give the same result as:

if(9 > 7){
if(7 < 9){
console.log('true');
}
}

Cybergenius:
No difference, they are both the same

like bruceleah said. i think there is a very subtle difference mostly in different scenarios and application.

blueyedgeek:
There really is no difference between both as they are basically different ways to do the same thing which is check to make sure that two expressions in the condition are met before any code statement is executed. The first method is a more compact form.

Just like we have the while and for loop, both are used for the same thing but the for loop allows you to keep all your code expressions in one statement making it a more compact form.

An example.

if(9 > 7 && 7 < 9){
console.log('true');
}

Will give the same result as:

if(9 > 7){
if(7 < 9){
console.log('true');
}
}

I quite agree with you. But what if we wanna check if 7 is less than 9 but equal to 8? The first example can't handle that but the second will

For instance:

f(9 > 7){
if(7 < 9){
console.log('true');
} else {
Console.write("8";
}
}

romme2u:


i love you assertion by bring two use case illustrating each scenario perfectly. in fact if it was a competition i may likely give it to you . but lets keep this open for further thoughts and opinions.

Thanks boss.

romme2u:


i love you assertion by bring two use case illustrating each scenario perfectly. in fact if it was a competition i may likely give it to you . but lets keep this open for further thoughts and opinions.

Thanks boss :-D

romme2u:


i love you assertion by bring two use case illustrating each scenario perfectly. in fact if it was a competition i may likely give it to you . but lets keep this open for further thoughts and opinions.

Thanks boss :-)

bruceleah has a higher insight which is mainly in their application. in between i am learning and enjoying it

more suggestions please

My network is kinda bad... I never intended to reply three times. Programmers abeg no vex

bruceleah:


I quite agree with you. But what if we wanna check if 7 is less than 9 but equal to 8? The first example can't handle that but the second will

For instance:

f(9 > 7){
if(7 < 9){
console.log('true');
} else {
Console.write("8";
}
}

I don't quite get you bro, what do you mean by checking if 7 is less than 9 but equal to 8?

By the way, If we add the else block to the first method, you'll get the same result anyway.

blueyedgeek:
I don't quite get you bro, what do you mean by checking if 7 is less than 9 but equal to 8?

By the way, If we add the else block to the first method, you'll get the same result anyway.

Sure boss, it would, I agree. But this might not be applicable to other scenarios like the first one I painted.

blueyedgeek:

There really is no difference between both as they are basically different ways to do the same thing which is check to make sure that two expressions in the condition are met before any code statement is executed. The first method is a more compact form.

Just like we have the while and for loop, both are used for the same thing but the for loop allows you to keep all your code expressions in one statement making it a more compact form.

An example.

if(9 > 7 && 7 < 9){
console.log('true');
}

Will give the same result as:

if(9 > 7){
if(7 < 9){
console.log('true');
}
}

Yes sir, and both snippets are practically useless as they have no logical implication. In other word, the presence or absence of the control structures will not in any way alter the flow of logic since they will both evaluate to TRUE.

Question, though both structures give the same result, is anyone better than the other? If so, which one?

...... or is it subject to end goal?

Regards.

bruceleah:


Sure boss, it would, I agree. But this might not be applicable to other scenarios like the first one I painted.

If you had passed a statement to be executed when the condition in the first if block is met and another statement to be executed if the second condition is met then it becomes something else.

Example:

if(9 > 7){
console.log('do something');
if(7 > 22){
console.log('do something else');
}
}

If this code is run, the statement in the first if block will be printed to the console and the second will be ignored. In this context, it does not do the same thing as using the
if(condition && condition){
//do something
}

but when you begin to nest multiple if statements and only one expression will be executed then they become the same thing. It doesn't matter how many nesting levels you go as far as all the if statements are used for one expression then it is the same thing as using the
if(condition && condition){
//do something
}

Example:

if(5 > 4){
if(6 > 5){
if(7 > 6){
if(8 > 7){
if(9 > 8 ) {
if(10 > 9){
console.log("This will only print if all conditions in the if statement are true" );
}
}
}
}
}
}

Is the same thing as:

Example:

if(5 > 4 && 6 > 5 && 7 > 6 && 8 > 7 && 9 > 8 && 10 > 9){
console.log("This will only print if all conditions in the if statement are true" );
}

Run both code snippets and you will get the exact same result. The second method is just a more compact form and more readable. There really is no difference.

GozieDiora:


Yes sir, and both snippets are practically useless as they have no logical implication. In other word, the presence or absence of the control structures will not in any way alter the flow of logic since they will both evaluate to TRUE.

Question, though both structures give the same result, is anyone better than the other? If so, which one?

...... or is it subject to end goal?

Regards.

In my opinion, none is better than the other. They are both identical in functionality and performance but I would favour the '&&' syntax over nesting multiple if statements since it is more readable.

welcome back sir.

blueyedgeek:
If you had passed a statement to be executed when the condition in the first if block is met and another statement to be executed if the second condition is met then it becomes something else.

Example:

if(9 > 7){
console.log('do something');
if(7 > 22){
console.log('do something else');
}
}

If this code is run, the statement in the first if block will be printed to the console and the second will be ignored. In this context, it does not do the same thing as using the
if(condition && condition){
//do something
}

but when you begin to nest multiple if statements and only one expression will be executed then they become the same thing. It doesn't matter how many nesting levels you go as far as all the if statements are used for one expression then it is the same thing as using the
if(condition && condition){
//do something
}

Example:

if(5 > 4){
if(6 > 5){
if(7 > 6){
if(8 > 7){
if(9 > 8 ) {
if(10 > 9){
console.log("This will only print if all conditions in the if statement are true" );
}
}
}
}
}
}

Is the same thing as:

Example:

if(5 > 4 && 6 > 5 && 7 > 6 && 8 > 7 && 9 > 8 && 10 > 9){
console.log("This will only print if all conditions in the if statement are true" );
}

Run both code snippets and you will get the exact same result. The second method is just a more compact form and more readable. There really is no difference.

I quite agree with you boss. Judging with this example, there's no difference. How about u explain this.

I want to check if a username actually exist in our database, and check if the password matches the specified user name.

Note: I want to let the user know if d specified user name exists in my db, I just don't want to throw a mismatch error.

I know it's not advisable as a programmer, let's just assume I wanna implement this. How wld u go about it?

bruceleah:


I quite agree with you boss. Judging with this example, there's no difference. How about u explain this.

I want to check if a username actually exist in our database, and check if the password matches the specified user name.

Note: I want to let the user know if d specified user name exists in my db, I just don't want to throw a mismatch error.

I know it's not advisable as a programmer, let's just assume I wanna implement this. How wld u go about it?

pseudo code

If username matches database && password matches as well --
'Successful log in''
Else
Throw error
'Username or password doesn't match database'

blueyedgeek:
pseudo code

If username matches database && password matches as well --
'Successful log in''
Else
Throw error
'Username or password doesn't match database'

Boss, I actually want to let the user know if the specified username exists in our db, not just match username and password (throw a username does not match database)

I also want to throw an error like "user does not exist in our database"

First check if user exist in db before matching username and password.

How would you go about it?

You guys have done justice to the topic kudos.

@bruceleah was correct all the way.

Both conditions look very similar If u r considering 2 conditions with no additional condition. But if u have multiple and complex conditions, they don't.

Let me add, the problem @ hand will determine which scenario to use.

The first 1 works best if I want to enter the block IF and only IF all the conditions are met.

The 2nd scenario is more of a step, entering into the the innermost block is only guaranteed if the outer block is true.

@bruceleah nice job. @op, nice argument.

blueyedgeek:

In my opinion, none is better than the other. They are both identical in functionality and performance but I would favour the '&&' syntax over nesting multiple if statements since it is more readable.

welcome back sir.

Well, from the stand point of computer programming purity and code optimisation, one is actually better.

Here is the gist:

In the first scenario (I.e. using the logical operator), compilers equiped with code optimisation functionality (like Object Pascal etc) take advantage of this structure to reduce total execution time by handling only one side of the operator in the best case scenario. In other words, the second side is executed if and only if the first part evaluates to be false (for logical OR). This goes a long way to increase speed and reduce run time memory consumption. However, this benefit can only be remarkable in data crunching programs like large file processing, batch processing especially in ERP's etc. IDE's like Netbeans for Java language, Morph X for X++ etc. which show approximate execution time would show this for very large amount of data.

In the second, still on logical OR, provided the first condition is true, the second must run.

So if OR is the intended logic, it would pay to use the first structure for code optimisation.

GozieDiora:


Well, from the stand point of computer programming purity and code optimisation, one is actually better.

Here is the gist:

In the first scenario (I.e. using the logical operator), compilers equiped with code optimisation functionality (like Object Pascal etc) take advantage of this structure to reduce total execution time by handling only one side of the operator in the best case scenario. In other words, the second side is executed if and only if the first part evaluates to be false (for logical OR). This goes a long way to increase speed and reduce run time memory consumption. However, this benefit can only be remarkable in data crunching programs like large file processing, batch processing especially in ERP's etc. IDE's like Netbeans for Java language, Morph X for X++ etc. which show approximate execution time would show this for very large amount of data.

In the second, still on logical OR, provided the first condition is true, the second must run.

So if OR is the intended logic, it would pay to use the first structure for code optimisation.

learnt from this post.

bruceleah:


Boss, I actually want to let the user know if the specified username exists in our db, not just match username and password (throw a username does not match database)

I also want to throw an error like "user does not exist in our database"

First check if user exist in db before matching username and password.

How would you go about it?

! == does not

if user && password match database
'Success'
Else if user !match && password match
'User does not match database'
Else if user match && password !match
'Incorrect password'
Else
'Incorrect user and password'

blueyedgeek:

! == does not

if user && password match database
'Success'
Else if user !match && password match
'User does not match database'
Else if user match && password !match
'Incorrect password'
Else
'Incorrect user and password'

I don't seem to understand line 3 of ur code.

What if this logic was simplified:

If (validUser(user)) {
If (validPword(user,pword)) {
// Do something
} else {
"Mismatch";
}
} else {
"No user";
}

Instead of

If (validUser(user) && validPword(user,pword)) {
//Do something
} else {
"Mismatch"
}

Note: the goal is to prompt user if user name does not exist and if there's a mismatch.

GozieDiora:


Well, from the stand point of computer programming purity and code optimisation, one is actually better.

Here is the gist:

In the first scenario (I.e. using the logical operator), compilers equiped with code optimisation functionality (like Object Pascal etc) take advantage of this structure to reduce total execution time by handling only one side of the operator in the best case scenario. In other words, the second side is executed if and only if the first part evaluates to be false (for logical OR). This goes a long way to increase speed and reduce run time memory consumption. However, this benefit can only be remarkable in data crunching programs like large file processing, batch processing especially in ERP's etc. IDE's like Netbeans for Java language, Morph X for X++ etc. which show approximate execution time would show this for very large amount of data.

In the second, still on logical OR, provided the first condition is true, the second must run.

So if OR is the intended logic, it would pay to use the first structure for code optimisation.

Great one boss, nice one.

I agree boss. Talking about code optimisation, remember that code would first be parsed, and den the semantics would be understood before it could be optimised.

My point: depending on the goal or the logic being used, result of parsing could be thesame and different.

Maybe be we try out different examples. We act as the compiler and try to parse our statements.

We'll see that in some cases we could generate the same parse tree for both conditions and in some, we won't.

So, both scenarios are different. in some cases they could look the same but they are ACTUALLY NOT (we could only figure this out acting as a compiler).

Just like boss GozieDiora has rightfully said, when writing codes, we need to consider the compilation & run time before implementing our logic.

bruceleah:


I don't seem to understand line 3 of ur code.

What if this logic was simplified:

...............
Note: the goal is to prompt user if user name does not exist and if there's a mismatch.

Though I prefer your approach, you seem to be forgetting we are dealing with pseudo codes here not programming languages. Functions are not to be imagined.

That aside, I think the goal is to prompt the user with his user name in case of password mismatch. In other words, if the user does not exist at all, the system simply tells the user but if the user name exists, the system should call the user by his name and ask if he forgot his password.

Just a slight modification of your code can achieve this.

bruceleah:


Great one boss, nice one.

I agree boss. Talking about code optimisation, remember that code would first be parsed, and den the semantics would be understood before it could be optimised.

My point: depending on the goal or the logic being used, result of parsing could be thesame and different.

Maybe be we try out different examples. We act as the compiler and try to parse our statements.

We'll see that in some cases we could generate the same parse tree for both conditions and in some, we won't.

So, both scenarios are different. in some cases they could look the same but they are ACTUALLY NOT (we could only figure this out acting as a compiler).

Just like boss GozieDiora has rightfully said, when writing codes, we need to consider the compilation & run time before implementing our logic.

Yeah, bro.

Let's not bother going into parsing/tokenisation (Backus Naur/ type 2 grammar) or semantic trees (Finit State Automata/ type 3 grammar). I'm sure a good number of peeps here won't flow along with us.

This is what differentiates a computer scientist from other computer programmers.

Lol. ... just kidding.