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<br>(from a default of '''9''') to '''200''' to accommodate when a root is closer to zero than the other root.
Note that only tennine decimal digits (precision) are shown in the ''displaying'' of the output.
This REXX version supports ''complex numbers'' for the result.
<lang rexx></lang>
<lang rexx>/*REXX program finds the roots (which may be complex) of a quadratic function.*/
'''{{out|output ''' |text= when using the input of: <tt> 1 -10e5 1 </tt> }}▼numeric digits 200 /*use enough digits to handle extremes.*/
parse arg a b c . /*obtain the specified arguments: A B C*/
call quadratic a,b,c /*solve quadratic function via the sub.*/
numeric digits 10 /*reduce (output) digits for human eyes*/
r1=r1/1; r2=r2/1; a=a/1; b=b/1; c=c/1 /*normalize numbers to the new digits. */
if r1j\=0 then r1=r1 || left('+',r1j>0)(r1j/1)"i" /*handle complex number.*/
if r2j\=0 then r2=r2 || left('+',r2j>0)(r2j/1)"i" /* " " " */
say ' a =' a /*display the normalized value of A. */
say ' b =' b /* " " " " " B. */
say ' c =' c /* " " " " " C. */
say; say 'root1 =' r1 /* " " " " 1st root*/
say 'root2 =' r2 /* " " " " 2nd root*/
exit /*stick a fork in it, we're all done. */
/*────────────────────────────────────────────────────────────────────────────*/
quadratic: parse arg aa,bb,cc /*obtain the specified three arguments.*/
$=sqrt(bb**2-4*aa*cc); L=length($) /*compute SQRT (which may be complex).*/
r=1/(aa+aa); ?=right($,1)=='i' /*compute reciprocal of 2*aa; Complex?*/
if ? then do; r1= -bb *r; r2=r1; r1j=left($,L-1)*r; r2j=-r1j; end
else do; r1=(-bb+$)*r; r2=(-bb-$)*r; r1j=0; r2j= 0; end
return
/*────────────────────────────────────────────────────────────────────────────*/
sqrt: procedure; parse arg x 1 ox; if x=0 then return 0; d=digits(); m.=9
numeric digits 9; numeric form; h=d+6; x=abs(x)
parse value format(x,2,1,,0) 'E0' with g 'E' _ .; g=g *.5'e'_ %2
do j=0 while h>9; m.j=h; h=h%2+1; end /*j*/
do k=j+5 to 0 by -1; numeric digits m.k; g=(g+x/g)*.5; end /*k*/
numeric digits d; return (g/1)left('i',ox<0) /*make complex if OX<0.*/</lang>
▲'''output''' when using the input of: <tt> 1 -10e5 1 </tt>
<pre>
a = 1
root2 = 0.000001
</pre>
The following output is when Regina 3.9.13 REXX is used.
'''{{out|output''' |text= when using the input of: <tt> 1 -10e9 1 </tt>}}
<pre>
a = 1
b = -100000000001.0E+10
c = 1
The following output is when R4 REXX is used.
'''{{out|output''' |text= when using the input of: <tt> 1 -10e9 1 </tt>}}
<pre>
a = 1
root2 = 0.0000000001
</pre>
'''{{out|output''' |text= when using the input of: <tt> 3 2 1 </tt>}}
<pre>
a = 3
c = 1
root1 = -0.3333333333333333333+0.4714045208i471404521i
root2 = -0.3333333333333333333-0.4714045208i471404521i
</pre>
'''{{out|output''' |text= when using the input of: <tt> 1 0 1 </tt>
<pre>
a = 1
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