30 lines
2.8 KiB
Rexx
30 lines
2.8 KiB
Rexx
/*REXX program mimics an "approximately equal to" for comparing floating point numbers*/
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numeric digits 15 /*what other FP hardware normally uses.*/
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@.= /*assign default for the @ array. */
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parse arg @.1 /*obtain optional argument from the CL.*/
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if @.1='' | @.1=="," then do; @.1= 100000000000000.01 100000000000000.011
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@.2= 100.01 100.011
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@.3= 10000000000000.001 / 10000 1000000000.0000001000
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@.4= 0.001 0.0010000001
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@.5= 0.00000000000000000000101 0.0
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@.6= sqrt(2) * sqrt(2) 2.0
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@.7= -sqrt(2) * sqrt(2) '-2.0'
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@.8= 3.14159265358979323846 3.14159265358979324
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/* added ───► */ @.9= 100000000000000003.0 100000000000000004.0
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end
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do j=1 while @.j\=='' /*process CL argument or the array #s. */
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say
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say center(' processing pair ' j" ",71,'═') /*display a title for the pair of #s. */
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parse value @.j with a b /*extract two values from a pair of #s.*/
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say 'A=' a /*display the value of A to the term.*/
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say 'B=' b /* " " " " B " " " */
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say right('A approximately equal to B?', 65) word("false true", 1 + approxEQ(a,b) )
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end /*j*/ /* [↑] right─justify text & true/false*/
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exit /*stick a fork in it, we're all done. */
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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approxEQ: procedure; parse arg x,y; return x=y /*floating point compare with 15 digits*/
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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sqrt: procedure; parse arg x; if x=0 then return 0; d=digits(); numeric digits; h=d+6
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numeric form; m.=9; parse value format(x,2,1,,0) 'E0' with g "E" _ .; g=g *.5'e'_ %2
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do j=0 while h>9; m.j=h; h=h%2+1; end /*j*/
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do k=j+5 to 0 by -1; numeric digits m.k; g=(g+x/g)*.5; end /*k*/; return g/1
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