Why does this work:
It seems that we're concatenating two literals:
std::cout << greeting + name + " Hello " + "There" << std::endl;
but if you remove (greeting + name +), it doesn't work ? 3 1879 Th******@cpp.co m wrote:
Why does this work:
It seems that we're concatenating two literals:
std::cout << greeting + name + " Hello " + "There" << std::endl;
but if you remove (greeting + name +), it doesn't work ?
operator+ is left associative. So what you get is:
(((greeting + name)) + " Hello ") + "There"
Assuming greeting and/or name is of type std::string, then it is easy to
follow along as see that each subexpression is a std::string.
Remove the (greeting + name +) and all you are left with is trying to
add two string literals, which does not result in concatenation. If you
want to concatenate two string literals, simply put them next to each
other with no operator:
std::cout << " Hello " "There" << std::endl;
This will concatenate them AT COMPILE TIME.
--
Alan Johnson
On Thu, 01 Mar 2007 15:09:49 -0800, Alan Johnson <aw***@yahoo.co m>
wrote:
>Th******@cpp.c om wrote:
>Why does this work:
It seems that we're concatenating two literals:
std::cout << greeting + name + " Hello " + "There" << std::endl;
but if you remove (greeting + name +), it doesn't work ?
operator+ is left associative. So what you get is: (((greeting + name)) + " Hello ") + "There"
But why are there three braces ? wouldn't two be enough ? like:
((greeting + name) + " Hello ") + "There"
it seems nicer ;-)
> Assuming greeting and/or name is of type std::string, then it is easy to follow along as see that each subexpression is a std::string.
Remove the (greeting + name +) and all you are left with is trying to add two string literals, which does not result in concatenation. If you want to concatenate two string literals, simply put them next to each other with no operator: std::cout << " Hello " "There" << std::endl;
This will concatenate them AT COMPILE TIME.
On 1 Mar, 22:41, TheCo...@cpp.co m wrote:
Why does this work:
It seems that we're concatenating two literals:
std::cout << greeting + name + " Hello " + "There" << std::endl;
but if you remove (greeting + name +), it doesn't work ?
to concat 2 string literals just remove the '+'. Then the preprocessor
does it for you. (Mainly useful to split a string literal over
multiple lines).
Welcome to another oddity of C++. If you don't like it you could
always try the D language where the syntax you are using would work
AFAIK
#include <string>
#include <iostream>
int main()
{
std::string greeting("somet hing"), name("name");
std::cout << greeting + " " + name + " Hello " "There\n";
}
regards
Andy Little This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
by: foodic |
last post by:
i am fresher to C++ programming, and I just
want to learn Concatenating Calls, I have
written a program,
class SetMe {
public:
void setX(int x) {_x = x;}
void setY(int y) {_y = y;}
void doubleMe()
|
by: Raymond |
last post by:
How does one concat string literals in pgsql ?
The compiler complains about the concat operator in the following code
fragment:
RAISE EXCEPTION
''SELECT DISTINCT "t1"."usesysid" '' ||
''INTO userID '' ||
''FROM "pg_user" AS "t1" '' ||
''WHERE "t1"."usename" = current_user '' ||
|
by: Richard Chen |
last post by:
Hi I want to construct a long string in C# in multiple lines therefore I
need a symbol to concatenate each line to the next line till the end of the
string.
In VB, there's a symbol "_" can be used at the end of each line. So what is
the equivalent in C#?
I don't like use "+" to separate a long string into multiple short ones
since it incurrs more double quotes.
|
by: Juan |
last post by:
Does any one know if there are reported bugs when concatenating strings?
When debugging each variable has the correct value but when I try to
concatenate them some values are missing (I can´t see them in the debugger).
After encoding the string (the sameone which complete value is not visible
from the debugger) all the values can be seen but they are spaced by big
amounts of zeros and use more that the 2048 bytes allocated. It is like if...
|
by: copx |
last post by:
Can you / are you supposed to free() string literals which are no longer
needed?
In my case I've menu construction code that looks like this:
menu_items = list_new();
list_add(menu_items, "Item 1");
list_add(menu_items, "Item 2");
list_add(menu_items, "Item 3");
menu_create(menu_items, false)
| |
by: c |
last post by:
Hi everybody.
I'm working on converting a program wriiten on perl to C, and facing a
problem with concatenate strings.
Now here is a small program that descripe the problem, if you help me
to solve in this small code, I can solve it on my own program...you
don't want to have head-ache :-)
So, the problem excatly is, I built an array..just like this one.
|
by: arnuld |
last post by:
i tried to output these 2 to the std. output:
const std::string hello = "Hello";
const std::string message = hello + ", world" + "!";
const std::string exclam = "!";
const std::string message2 = "hello" + " world" + exclam;
the first one runs fine but 2nd does not as we can not combine 2
|
by: Mary |
last post by:
I have a student who has a hyphenated first name. If I concatenate the
name like this: StudentName:( & ", " &
), it works as expected. If, however, I try to get
the first name first by concatenating like this: StudentName:
( & " " & ), only the first name
appears.
I sure would appreciate any help!
Mary
|
by: SasQ |
last post by:
Hello.
I wonder if literal constants are objects, or they're only
"naked" values not contained in any object?
I have read that literal constants may not to be allocated
by the compiler. If the Standard is saying that "object is
a region of storage", I deduce from that that literal constants
aren't objects because they may not be alocated as regions of
storage in the memory.
|
by: marktang |
last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look !
Part I. Meaning of...
|
by: Oralloy |
last post by:
Hello folks,
I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>".
The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed.
This is as boiled down as I can make it.
Here is my compilation command:
g++-12 -std=c++20 -Wnarrowing bit_field.cpp
Here is the code in...
| |
by: jinu1996 |
last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth.
The Art of Business Website Design
Your website is...
|
by: tracyyun |
last post by:
Dear forum friends,
With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
|
by: agi2029 |
last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own....
Now, this would greatly impact the work of software developers. The idea...
|
by: TSSRALBI |
last post by:
Hello
I'm a network technician in training and I need your help.
I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs.
The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols.
I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
|
by: adsilva |
last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
|
by: 6302768590 |
last post by:
Hai team
i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
| |
by: muto222 |
last post by:
How can i add a mobile payment intergratation into php mysql website.
| |