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Elliptic curve arithmetic: Difference between revisions
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→{{header|REXX}}: fixed a typo, added/changed comments and whitespace, changed alignments.
m (split long paragraphs, added whitespace and highlighting to the task's preamble.) |
m (→{{header|REXX}}: fixed a typo, added/changed comments and whitespace, changed alignments.) |
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Also, some code was added to have the output better aligned (for instance, negative and positive numbers).
<lang rexx>/*REXX program defines (for any 2 points on the curve), returns the sum of the 2 points.*/
numeric digits 100 /*try to ensure a min. of accuracy loss*/
a=func(1) ; say 'a = ' show(a)
b=func(2) ; say 'b = ' show(b)
c=add(a, b) ; say 'c = (a+b) =' show(c)
d=neg(c) ; say 'd = -c =' show(d)
e=add(c, d) ; say 'e = (c+d) =' show(e)
g=add(a, add(b, d)) ; say 'g = (a+b+d) =' show(g)
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
cbrt: procedure; parse arg x; return root(x,3)
root: procedure; parse arg x,y; if x=0 | y=1 then return x/1; d=5; return rootI()/1
rootG: parse value format(x,2,1,,0) 'E0' with ? 'E' _ .; return (?/y'E'_ %y) + (x>1)
func: procedure; parse arg y,k; if k=='' then k=7; return cbrt(y**2-k) y
inf: return '1e' || (digits()%2)
isZ: procedure; parse arg px .; return abs(px) >= inf()
neg: procedure; parse arg px py; return px (-py)
show: procedure; parse arg x y; return conv(x) conv(y)
zero: return inf() inf()
/*──────────────────────────────────────────────────────────────────────────────────────*/
add: procedure; parse arg px py, qx qy; if px=qx & py=qy then return dbl(px py)
if isZ(px py) then return qx qy; if isZ(qx qy) then return px py
z=qx-px; if z=0 then do; $=inf(); rx=inf(); end
else do; $=(qy-py)/z; rx=$**2 - px - qx; end
ry=$ * (px-rx) - py
return rx ry
/*──────────────────────────────────────────────────────────────────────────────────────*/
conv: procedure; parse arg z; if isZ(z) then return 'zero'
return left('',z>=0)format(z,,5)/1
/*──────────────────────────────────────────────────────────────────────────────────────*/
dbl: procedure; parse arg px py;
if z=0 then $=inf()
else $=(3*px*py) / (py*2)
rx=$**2 - 2*px; ry=$ * (px-rx) - py
return rx
/*──────────────────────────────────────────────────────────────────────────────────────*/
rootI:
'''output'''
<pre>
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