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Roots of a function: Difference between revisions
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i = i + 1
END DO</lang>
=={{header|freebasic}}==
Simple bisection method.
<lang freebasic>
#include "crt.bi"
const iterations=20000000
sub bisect( f1 as function(as double) as double,min as double,max as double,byref O as double,a() as double)
dim as double last,st=(max-min)/iterations,v
for n as double=min to max step st
v=f1(n)
if sgn(v)<>sgn(last) then
redim preserve a(1 to ubound(a)+1)
a(ubound(a))=n
O=n+st:exit sub
end if
last=v
next
end sub
function roots(f1 as function(as double) as double,min as double,max as double, a() as double) as long
redim a(0)
dim as double last,O,st=(max-min)/iterations,v
for n as double=min to max step st
v=f1(n)
if sgn(v)<>sgn(last) and n>min then bisect(f1,n-st,n,O,a()):n=O
last=v
next
return ubound(a)
end function
Function CRound(Byval x As Double,Byval precision As Integer=30) As String
If precision>30 Then precision=30
Dim As zstring * 40 z:Var s="%." &str(Abs(precision)) &"f"
sprintf(z,s,x)
If Val(z) Then Return Rtrim(Rtrim(z,"0"),".")Else Return "0"
End Function
function defn(x as double) as double
return x^3-3*x^2+2*x
end function
redim as double r()
print
if roots(@defn,-20,20,r()) then
print "in range -20 to 20"
print "All roots approximate"
print "number","root to 6 dec places","function value at root"
for n as long=1 to ubound(r)
print n,CRound(r(n),6),,defn(r(n))
next n
end if
sleep
</lang>
<pre>
in range -20 to 20
All roots approximate
number root to 6 dec places function value at root
1 0 -2.929925652002424e-009
2 1 1.477781779325033e-009
3 2 -2.897852187377925e-009
</pre>
=={{header|Go}}==
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