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Join Date: Sep 2004
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Newbie Poster
I'm having problem writing code for a program that estimates the value of the mathematical constant e by using this formula e= 1 + 1/1! + 1/2!...
I just cant get this to work. Can someone please help
I just cant get this to work. Can someone please help
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Join Date: Feb 2002
Location: Lawn Guylen, NY
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Hmm ... start by writing a recurisve function to find the factorial of a number. There's a tutorial on recursion in either the C++ or the Computer Science section of this site - I forget which. You should also be able to find this function by doing a quick google search. Then just add 1/ to your factorial equation and it should do the trick 
Dani the Computer Science Gal
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Join Date: Sep 2004
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i guess it worked. I'm getting 0 as the answer. who knows.
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how do you get to calculae a power. is it pow(...)
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Join Date: Sep 2004
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>how do you get to calculae a power. is it pow(...)
Yes, that's one way.
Yes, that's one way.
I'm a programmer. My attitude starts with arrogance, holds steady at condescension, and ends with hostility. Get used to it.
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Join Date: Oct 2004
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Light Poster
I know that I'm breaking the rule not to make anybody's homwork.
But since the answer is so simple I can not help it to post a solution
K.
But since the answer is so simple I can not help it to post a solution
#include <iostream>
double fakt(int i)
{
if ( i == 1 )
return 1.0;
return fakt( i -1 ) * i;
}
int main() {
double e = 1.0;
for ( int i = 1; i < 4000; i++ ) {
e += 1.0 / fakt(i);
}
std::cout << " e = " << e << std::endl;
return 0;
} •
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Join Date: Oct 2004
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@ Narue: you are right that 170! is the largest nr. that fits into a double.
but with my compiler the result is still correct because fact() simply returns inf for larger numbers then 170 and 1/inf returns 0.0 (btw I'm using gcc )
K.
but with my compiler the result is still correct because fact() simply returns inf for larger numbers then 170 and 1/inf returns 0.0 (btw I'm using gcc )
K.
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>but with my compiler the result is still correct
That's nice, but your code is still wrong even if the compiler that you use happens to interpret "undefined" as something intelligent.
That's nice, but your code is still wrong even if the compiler that you use happens to interpret "undefined" as something intelligent.
I'm a programmer. My attitude starts with arrogance, holds steady at condescension, and ends with hostility. Get used to it.
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Join Date: Oct 2004
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Originally Posted by Narue
>but with my compiler the result is still correct
That's nice, but your code is still wrong even if the compiler that you use happens to interpret "undefined" as something intelligent.
K.
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>explain why I did not recognize the mistake in the first place.
I can understand not knowing that floating-point overflow is undefined, but it should be immediately obvious that a double couldn't possibly hold a factorial anywhere close to 3999!.
>but code snippets should be seen as starting points or suggestions, not finished product.
I agree. Unfortunately, those that we help aren't quite so forgiving. They have a tendency to see code we post as set in stone answers that "must" be correct. As such, rather than end up teaching bad habits, we should try to be as accurate and correct as possible.
>None of the snippets or suggestions I make are ones I've built and tested
That's your choice. I prefer to only post code that I've made sure works as expected. However, you should mention that your code wasn't tested and you only "hope" that it works.
>only ideas to get the thread-opener's juices flowing.
That's fine, I do it myself. But I make sure that the example is still correct so that the juices aren't sour.
>Some of my posts have been nit picked for syntax or stuff that misses the bigger picture
That's a rather narrow view I think. It seems to me that it was you who missed the bigger picture. If you don't want to be nitpicked on syntax then give pseudocode. It still conveys the idea and avoids people like me who think that teachers should make an attempt at being correct because they're viewed as role models.
>but please try to have a little patience with those of us who can't devote as much time to posts as you.
I have very little time to devote to posts despite what you may think, but I still manage to check my answers. Thus I have very little patience for people who are either too lazy or too arrogant to make sure that they're right.
I can understand not knowing that floating-point overflow is undefined, but it should be immediately obvious that a double couldn't possibly hold a factorial anywhere close to 3999!.
>but code snippets should be seen as starting points or suggestions, not finished product.
I agree. Unfortunately, those that we help aren't quite so forgiving. They have a tendency to see code we post as set in stone answers that "must" be correct. As such, rather than end up teaching bad habits, we should try to be as accurate and correct as possible.
>None of the snippets or suggestions I make are ones I've built and tested
That's your choice. I prefer to only post code that I've made sure works as expected. However, you should mention that your code wasn't tested and you only "hope" that it works.
>only ideas to get the thread-opener's juices flowing.
That's fine, I do it myself. But I make sure that the example is still correct so that the juices aren't sour.
>Some of my posts have been nit picked for syntax or stuff that misses the bigger picture
That's a rather narrow view I think. It seems to me that it was you who missed the bigger picture. If you don't want to be nitpicked on syntax then give pseudocode. It still conveys the idea and avoids people like me who think that teachers should make an attempt at being correct because they're viewed as role models.
>but please try to have a little patience with those of us who can't devote as much time to posts as you.
I have very little time to devote to posts despite what you may think, but I still manage to check my answers. Thus I have very little patience for people who are either too lazy or too arrogant to make sure that they're right.
I'm a programmer. My attitude starts with arrogance, holds steady at condescension, and ends with hostility. Get used to it.
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