Kahan summation: Difference between revisions
Added Gambas y True BASIC
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Kahan sum = 1.0000000000000000
</pre>
=={{header|BASIC}}==
==={{header|Gambas}}===
{{trans|FreeBASIC}}
<syntaxhighlight lang="vbnet">Public a As Float
Public b As Float
Public c As Float
Function KahanSum(a As Float, b As Float, c As Float) As Float
Dim sum As Float = 0.0
Dim i As Float, y As Float, t As Float
c = 0.0
For i = 1 To a
y = i - c
t = sum + y
c = (t - sum) - y
sum = t
Next
Return sum
End Function
Function epsilon() As Float
Dim eps As Float = 1
While (1 + eps <> 1)
eps /= 2
Wend
Return eps
End Function
Public Sub Main()
a = 1.0
b = epsilon()
c = -b
Dim s As Float = (a + b) + c
Dim k As Float = KahanSum(a, b, c)
Dim d As Float = k - s
Print "Epsilon = "; b
Print "(a + b) + c = "; s
Print "Kahan sum = "; k
Print "Delta = "; d
End</syntaxhighlight>
{{out}}
<pre>Epsilon = 1,11022302462516E-16
(a + b) + c = 1
Kahan sum = 1
Delta = 1,11022302462516E-16</pre>
==={{header|True BASIC}}===
<syntaxhighlight lang="qbasic">
FUNCTION epsilon
LET eps = 1
DO while (1+eps <> 1)
LET eps = eps/2
LOOP
LET epsilon = eps
END FUNCTION
FUNCTION kahansum(a, b, c)
LET sum = 0
LET c = 0
FOR i = 1 to a
LET y = i-c
LET t = sum+y
LET c = (t-sum)-y
LET sum = t
NEXT i
LET kahansum = sum
END FUNCTION
LET a = 1
LET b = epsilon
LET c = -b
LET s = (a+b)+c
LET k = kahansum(a, b, c)
LET d = k-s
PRINT "Epsilon ="; b
PRINT "(a + b) + c ="; s
PRINT "Kahan sum ="; k
PRINT "Delta ="; d
END</syntaxhighlight>
{{out}}
<pre>Epsilon = 1.110223e-16
(a + b) + c = 1.
Kahan sum = 1
Delta = 1.110223e-16</pre>
=={{header|C}}==
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