Defining functions outside main - problem

I am trying to define a function outside main, and the function will be used inside a loop(think thats where my probelms lie), here are the relevant bits of code. would be grateful of any help you could give me some advice/help (NB: i have attached the full code):

Code:

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float f1(float Co1[10], float x3[100], int i);

int main ()

(

.....

float Co[10]; float x[100]; int i;


int result;

for(i=0;i<15;i++)
{
result= f1(Co, x, i);

coutf(x)= "<<result<<endl;

if(fabs(f1(Co,x,i))<0.00000001)
{
cout<<"The value of f(x) at the root is: "<<result<<endl;
cout<<endl;
return(0);
}
}
}


float f1(float Co[10], float x[100], int i)
{
float result;
result=((Co1[0]*x[i]*x[i])+(Co1[1]*x[i])+Co1[2]);
return(result);
}

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Quote:

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NB: i have attached the full code

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Maybe that code will erase every file on my computer.

i didnt know you could do that with a cpp! erm, i have now written the vital bits of code in. sorry

Umm, so what's the problem? It looks like you fixed the syntax error.

it doesnt build, come up with a few errors, argument from int to float, assignment from int to float

redefintions of i and undeclared variables, sort those errors out.

redefinitions of i and undeclared variables......as in ive used i twice? dont really understand what your saying.

yes thats what it means. i run your prog on my machine and this is what it comes up with.

Quote:

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ompiling...
test3232.cpp
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(7) : error C2143: syntax error : missing ')' before ';'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(7) : error C2091: function returns function
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before 'for'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ')' before ';'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '<'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2501: 'i' : missing storage-class or type specifiers
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2086: 'i' : redefinition
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '<'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '++'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2501: 'i' : missing storage-class or type specifiers
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2086: 'i' : redefinition
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2143: syntax error : missing ';' before '++'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(12) : error C2059: syntax error : ')'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(13) : error C2143: syntax error : missing ';' before '{'
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(13) : error C2447: missing function header (old-style formal list?)
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(16) : error C2001: newline in constant
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2065: 'Co1' : undeclared identifier
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2109: subscript requires array or pointer type
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2109: subscript requires array or pointer type
D:\Program Files\Microsoft Visual Studio\MyProjects\test3232\test3232.cpp(31) : error C2109: subscript requires array or pointer type
Error executing cl.exe.

test3232.obj - 20 error(s), 0 warning(s)

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:( oh dear, i still dont understand what i have to change though! argh

When I downloaded the attachment, I only received one error and one warning. The error was on the line:

Code:

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if(fabs(f1(i))<E)
//looks like it should be
if(fabs(f1(Co, x, i))<E)

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And the warning is:
"warning C4244: '=' : conversion from 'float' to 'int', possible loss of data"
on this line:

Code:

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result= f1(Co, x, i);

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yeah, but what does that mean? does no-one here actually know what this is? or does everyone just copy it without understanding it???

Quote:

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but what does that mean

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f1() takes a float as an argument, but you are trying to pass an int. It is possible to cast to float, but then f1() takes 3 arguments, and you only provide one, so the problem runs deeper than that.

ok, im starting to understand a bit more, my programme takes f1 to be float but wants to make it an int? how do i fix the problem? i've tried everything to try and get it to work and nothing is working!

Before you start thinking about casting, examine:

Code:

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float f1(float Co1[10], float x3[100], int i);

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and its use in:

Code:

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f1(i)

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Can you see what's wrong?

no, i was told by my supervisor that i was meant to write f1 as a function of i when it was in the loop!
can you at least tell me which bit is wrong, the float f1(....) or the f1(...) bit?

Quote:

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i was told by my supervisor that i was meant to write f1 as a function of i when it was in the loop!

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I see. What does f1() do, and why on earth do you name it f1 when you can use a more descriptive name?

ok, ill change it! it is a function that is defined outside of int main. it has to compute values of a function at each iteration step in a loop statement. hence it is dependent on i! i have defined it at the top outside main, and then put the formula at the bottom after my return(0) }. the problem is that im not sure how to make it use the formula for each iteration step, also i have arrays in there, so it complicates it even further and puts it outside of my knowledge!