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author | Peter Drahoš <drahosp@gmail.com> | 2014-02-19 12:36:10 +0100 |
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committer | Peter Drahoš <drahosp@gmail.com> | 2014-02-19 12:36:10 +0100 |
commit | f8a616eedabd607c13b4b78427d184c600a32665 (patch) | |
tree | 128ad33a2868e40ec984d6d098837d36edc9f3ac /share/lua/test/bisect.lua | |
download | lua-Darwin-x86_64.tar.gz |
[luadist-git] add lua-5.1.5-Darwin-x86_64 [ci skip]5.1.5-Darwin-x86_64Darwin-x86_64
Diffstat (limited to 'share/lua/test/bisect.lua')
-rw-r--r-- | share/lua/test/bisect.lua | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/share/lua/test/bisect.lua b/share/lua/test/bisect.lua new file mode 100644 index 0000000..f91e69b --- /dev/null +++ b/share/lua/test/bisect.lua @@ -0,0 +1,27 @@ +-- bisection method for solving non-linear equations + +delta=1e-6 -- tolerance + +function bisect(f,a,b,fa,fb) + local c=(a+b)/2 + io.write(n," c=",c," a=",a," b=",b,"\n") + if c==a or c==b or math.abs(a-b)<delta then return c,b-a end + n=n+1 + local fc=f(c) + if fa*fc<0 then return bisect(f,a,c,fa,fc) else return bisect(f,c,b,fc,fb) end +end + +-- find root of f in the inverval [a,b]. needs f(a)*f(b)<0 +function solve(f,a,b) + n=0 + local z,e=bisect(f,a,b,f(a),f(b)) + io.write(string.format("after %d steps, root is %.17g with error %.1e, f=%.1e\n",n,z,e,f(z))) +end + +-- our function +function f(x) + return x*x*x-x-1 +end + +-- find zero in [1,2] +solve(f,1,2) |