Factorial Calculator

[josh]

I have to make a program that accepts a number between 1 and 30 from the user and then calcualte the factorial of the number. The code I have so far when I input the number 4 it says the factorial is 0 when it should be 24.

here is my code:

code:

%---------------------------------------------------------------------------- %Factorial Calculator %By: Josh Rosen %Date: October 3, 2004. %Version: 1.0.0 % %Input: A number between 1 and 30 %Output: The factorial of the inputted number %Process: Use a loop to continue. Use a for loop within the continuous loop to calculate. %---------------------------------------------------------------------------- %Declare Variables var fact : int          %The factorial of the inputed number var num : int           %The number to calculate the factorial for var cont : string       %Holds the users answer to continue or not %Continuous loop loop     cls     put "What number would youy like to calculate the factorial of? (number must be between 1 and 30)"     get num     fact := num     for decreasing i : num .. 1         fact:= i*(i-1)     end for     put "The factorial of ", num, " is ", fact     put ""     put "Do you wish to continue? Y/N"     get cont     exit when cont = "N" or cont = "n" end loop

Can someone tell me what I am doing wrong. I know it has something to do with my equation inside of the for loop.

thanx

[Tony]

code:

for decreasing i : num .. 1         fact:= i*(i-1)

i decreases down to 1, at which point it is

code:

fact := 1 * (1 - 1)

1 * 0 is clearly 0
what you want is

code:

fact := 1 for i : 1 .. num         fact:= fact * i end for

[josh]

Thanx for the help.

I should have realized that.

[wtd]

The recursive solution is simpler by far.

code:

function factorial(n : int) : int    if n = 1 then       result 1    else       result n * factorial(n - 1)    end if end factorial

[josh]

I am in grade 10 compsci adn we havent learnt functions yet. I know about them from Java but my teach wanted us to use loops within loops.

[apomb]

just a question rysticlight, you learned java before Turing!? why??

i started turing in gr 10 programming then java in gr 11 ... i found that the ppl that didnt have the background in turing didint do as well, is/was this the case in your class?

[josh]

I took a two week course over the summer where you learn game programming in Java, made my own asteroids game which I am tryign to figure out how to compile so I can post here. I use eclipse.

there are difingntly alot of ppl in my class who should not be here but since we are learning turing I thik they will be O.k. My school does turing in grade 10, VB in grade 11, and Java in grade 12

[apomb]

WOW ... thats a kinda back asswards approach, although VB is Very object oriented and has some similarities to java (note some meaning none) however, have they ever considered C++ in 12 and JAVA in 11 and turing in 10 ... (and Flash, javascript and html in Gr 12-web developing)

[Tony]

vb is not object oriented... atleast not in the sence its taught

and the bottom line is that schools teach whatever the teacher wants.. or rather whatever your teacher might have a remote knowledge of

[josh]

no I don't think my school would ever consider C++ right now (even though they have Visual C++ ) but I think this is the first year they did Java in grade 12.

and tony my skool hgas no web developing course that I know of (they do a bit of flash in comtech)

[apomb]

well, i guess that just shows how noobish i can be ... i must have confused "click and drag" with object oriented... i guess. and visual C++ is the same as regular C++ except that it has different classes or it uses microsoft crap... ill stop talking now on grounds i dont know what im talking about

tony wrote:

and the bottom line is that schools teach whatever the teacher wants.. or rather whatever your teacher might have a remote knowledge of

good point too tony, i was merely stating what was toght at my school, and wondering about methods at different schools, that is all

[wtd]

For what it's worth, VB.NET is very object-oriented. That doesn't make it good, but it's more important to know why a language sucks than just that it does.