Help please !!! No if...else statements.

[farah727rash]

Hey All,
This is a program to extract the middle name from a person's full name,
but it only works for a person who has a first, middle and a last name.
What do I do so that it works for a person who has just a first and
last name? For example: Fabio or Santa Claus. I am not supposed to use
conditional statements, other wise using if...else it would have been
so easy. I can't think of a way to do it without if...else. Any
ideas/suggestions would be great. Thanks a lot, Farah.


/*
----------------------------------------------------------------------
Program: Program 6.cpp
Purpose: This program extracts the middle name from a person's full
name
Written: Farah Rasheed
Date : 10/12/06
Version: .NET
------------------------------------------------------------------------*/

#include <iostream>
#include <string>
#include <cmath>

using namespace std;

int main(void)
{
// Purpose of the program
cout << "The program reads your full name extracts the middle name."
<< endl << endl;

// Read in the full name
cout << "Enter your full name: ";
cin.ignore();
string name;
getline(cin, name, '\n');

int lastBlankPos = name.rfind(" ");
int nextToLastBlankPos = name.find(" ", 0);
int length_of_middle_name = lastBlankPos-nextToLastBlankPos;
//cout << lastBlankPos << "\t" << nextToLastBlankPos << "\t" <<
length_of_middle_name<<"\n";

string middle_name = name.substr(nextToLastBlankPos,
length_of_middle_name);

cout << middle_name << endl << endl;

// End of the program
return 0;
}

 

[Kai-Uwe Bux]

Hey All,
This is a program to extract the middle name from a person's full name,
but it only works for a person who has a first, middle and a last name.
What do I do so that it works for a person who has just a first and
last name? For example: Fabio or Santa Claus. I am not supposed to use
conditional statements, other wise using if...else it would have been
so easy. I can't think of a way to do it without if...else. Any
ideas/suggestions would be great.

[snip]

I consider such puzzles rather pointless. But anyway, one way to fake an
if-statement comes to mind: you can exploit [5.14/1] which says that
boolean expressions use conditional evaluation, i.e., when you write

condition && some_boolean_func( args );

then some_boolean_func( args ) is only evaluated when condition is true.


Best

Kai-Uwe Bux

 

[Moonlit]

Hi,

Can't you use?:

string Dummy, Middlename;
stream >> Dummy >> Middlename;



cout << Middlename;

Regards, Ron AF Greve

http://moonlit.xs4all.nl

 

[Moonlit]

Oops sorry didn't read your post very well :-(



Regards, Ron AF Greve

http://moonlit.xs4all.nl

 

[Frederick Gotham]

(e-mail address removed) posted:

This is a program to extract the middle name from a person's full name,
but it only works for a person who has a first, middle and a last name.

Possible strategy:

View the string as

[sequence of characters] space [sequence of characters] space [sequence
of characters] nullterminator

What do I do so that it works for a person who has just a first and
last name? For example: Fabio or Santa Claus.

You don't. You'll have to make one up for them. May I suggest "Jason"?

I am not supposed to use conditional statements, other wise using
if...else it would have been so easy.

Ther ternary operator is your friend.

I can't think of a way to do it without if...else.

int main(void)
{
// Purpose of the program
cout << "The program reads your full name extracts the middle name."
<< endl << endl;

You must include <ostream> to make use of "endl".

Here's a possible algorithm:

#include <cassert>
#include <cstring>
#include <string>

bool EnsureAtLeastTwoWordsFollowedByOneSpaceEach(char const *p)
{
assert(p);

char const *q = std::strchr(p,' ');

if(!q || (q==p)) return false;

p = std::strchr(++q,' ');

if(!p || (q==p)) return false;

return true;
}

std::string ExtractSecondWord(char const *p)
{
p = std::strchr(p,' ') + 1;

char const *const plast = std::strchr(p,' ');

return std::string(p,plast);
}

#include <iostream>
#include <ostream>

int main()
{
std::cout << "Enter three words: ";

std::string str;

std::getline(std::cin,str);

char const *p;

if (EnsureAtLeastTwoWordsFollowedByOneSpaceEach(p = str.c_str()))
std::cout << "\n\n" << ExtractSecondWord(p) << std::endl;
}


It really depends on what exactly you're trying to do...

 

[farah727rash]

Thanks for the help, but like I said, this is tje intro to C++ course,
and we have just had three one-and-half-hour lectures till now. so, all
this stuff is really way over my head. Can't you think of something
simple our professor wants from us instead? Thanks again, Farah.

(e-mail address removed) posted:

This is a program to extract the middle name from a person's full name,
but it only works for a person who has a first, middle and a last name.

Possible strategy:

View the string as

[sequence of characters] space [sequence of characters] space [sequence
of characters] nullterminator

What do I do so that it works for a person who has just a first and
last name? For example: Fabio or Santa Claus.

You don't. You'll have to make one up for them. May I suggest "Jason"?

I am not supposed to use conditional statements, other wise using
if...else it would have been so easy.

Ther ternary operator is your friend.

I can't think of a way to do it without if...else.

int main(void)
{
// Purpose of the program
cout << "The program reads your full name extracts the middle name."
<< endl << endl;

You must include <ostream> to make use of "endl".

Here's a possible algorithm:

#include <cassert>
#include <cstring>
#include <string>

bool EnsureAtLeastTwoWordsFollowedByOneSpaceEach(char const *p)
{
assert(p);

char const *q = std::strchr(p,' ');

if(!q || (q==p)) return false;

p = std::strchr(++q,' ');

if(!p || (q==p)) return false;

return true;
}

std::string ExtractSecondWord(char const *p)
{
p = std::strchr(p,' ') + 1;

char const *const plast = std::strchr(p,' ');

return std::string(p,plast);
}

#include <iostream>
#include <ostream>

int main()
{
std::cout << "Enter three words: ";

std::string str;

std::getline(std::cin,str);

char const *p;

if (EnsureAtLeastTwoWordsFollowedByOneSpaceEach(p = str.c_str()))
std::cout << "\n\n" << ExtractSecondWord(p) << std::endl;
}


It really depends on what exactly you're trying to do...

 

[gw7rib]

Hey All,
This is a program to extract the middle name from a person's full name,
but it only works for a person who has a first, middle and a last name.
What do I do so that it works for a person who has just a first and
last name? For example: Fabio or Santa Claus. I am not supposed to use
conditional statements, other wise using if...else it would have been
so easy. I can't think of a way to do it without if...else. Any
ideas/suggestions would be great. Thanks a lot, Farah.

How about something along the following lines? I'm assuming that the
name which goes in is a c-type string, and that you are allowed to
modify it (for example, it's not a literal). You were only wanting a
hint so I'll happily leave any necessary modifications up to you...

char *middlename(char *name) {
char *b, *e;

for (b = name; name != 0 && name != ' '; b++);

for (e = name + strlen(name) - 1; e > b && name[e] != ' '; e--);

name[e] = 0;

return name+b;
}

This is completely untested, but the idea is that -

firstly we set b to where the second name starts, or the end of the
string if there is only one name;

secondly, we set e to where the final name starts, but not going back
before b

we mark e as the end of the string to return

we return the string starting from b

As it stands, the returned string will have more spaces than you want,
but it should at least fish out the required name. Hope it is helpful!

Paul.

 

[dieu.tout.puissant]

You can replace, in your name string, the first and last name by an
error message. Thus, if the whole name has less than 3 separate parts,
you will extract an error message instead of a middle name.

Here is an implementation of this trick (I tried to indroduce as few
new concepts as possible):

#include <iostream>
#include <string>
#include <cmath>

using namespace std;

int main(void)
{
// Purpose of the program
cout << "The program reads your full name extracts the middle name."
<< endl << endl;

// Read in the full name
cout << "Enter your full name: ";
string name;
getline(cin, name, '\n');

// Replace last name by an error message
int lastBlankPos = name.rfind(" ") + 1;
name.replace(lastBlankPos,name.size(),"<error>");

// Replace first name by an error message
int firstBlankPos = name.find(" ");
name.replace(0,firstBlankPos,"<error>");

//Take the middle name from the newly constructed name
firstBlankPos = name.find(" ") + 1;
lastBlankPos = name.rfind(" ");

int length_of_middle_name = lastBlankPos-firstBlankPos;
string middle_name = name.substr(firstBlankPos,
length_of_middle_name);
cout << middle_name << endl << endl;

// End of the program
return 0;
}

The design and syntax of the program can be improved depending on your
c++ knowledge.

 

[gw7rib]

Hey All,
This is a program to extract the middle name from a person's full name,
but it only works for a person who has a first, middle and a last name.
What do I do so that it works for a person who has just a first and
last name? For example: Fabio or Santa Claus. I am not supposed to use
conditional statements, other wise using if...else it would have been
so easy. I can't think of a way to do it without if...else. Any
ideas/suggestions would be great. Thanks a lot, Farah.

How about something along the following lines? I'm assuming that the
name which goes in is a c-type string, and that you are allowed to
modify it (for example, it's not a literal). You were only wanting a
hint so I'll happily leave any necessary modifications up to you...

char *middlename(char *name) {
char *b, *e;

for (b = name; name != 0 && name != ' '; b++);

for (e = name + strlen(name) - 1; e > b && name[e] != ' '; e--);

name[e] = 0;

return name+b;
}

Whoops! You can either use character pointers for b and e, or have then
as ints indicating a position in name, but you do have to decide
which... Here are a couple of versions which have survived a minimal
amount of testing:

char *middlename1(char *name) {
char *b, *e;


for (b = name; *b != 0 && *b != ' '; b++);


for (e = name + strlen(name) - 1; e > b && *e != ' '; e--);

while (b < e && *b == ' ') b++;
while (e > b && *(e-1) == ' ') e--;

*e = 0;

return b;
}

or

char *middlename2(char *name) {
int b, e;


for (b = 0; name != 0 && name != ' '; b++);


for (e = strlen(name) - 1; e > b && name[e] != ' '; e--);

while (b < e && name == ' ') b++;
while (e > b && name[e-1] == ' ') e--;

name[e] = 0;


return name+b;
}