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Horizontal sundial calculations: Difference between revisions
m
→{{header|REXX}}: added/changed wording in the REXX section header, added/changed comments and whitespace, optimized the ATAN function.
(→{{header|Kotlin}}: Updated example see https://github.com/dkandalov/rosettacode-kotlin for details) |
m (→{{header|REXX}}: added/changed wording in the REXX section header, added/changed comments and whitespace, optimized the ATAN function.) |
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Line 2,030:
=={{header|REXX}}==
The REXX language doesn't have the usual
<br>so these as well as '''pi''' were added to this program.
No attempt was made to explain the inner workings of the trigonometric functions.
<lang rexx>/*REXX program displays: hour, sun hour angle, dial hour line angle, 6am ───► 6pm. */
numeric digits 60 /*
parse arg lat lng mer . /*obtain optional arguments from the CL*/
/* ┌───────────◄ None specified? Then use the default*/
Line 2,042 ⟶ 2,043:
if lng=='' | lng=="," then lng= -150.5 /* " " " " " " */
if mer=='' | mer=="," then mer= -150 /* " " " " " " */
L=max(length(lat), length(lng), length(mer) ) /*find maximum length of three numbers.*/▼
say ' latitude:' right(lat, L) /*display the latitude to the terminal*/▼
say ' longitude:' right(lng, L) /* " " longitude " " " */▼
sineLat=sin( d2r(lat) ) /*calculate sine of (radian) latitude. */
w1=max( length('hour'
w2=max( length('sun hour'
w3=max( length('dial hour'), length("line angle")) + 2
▲L=max(length(lat), length(lng), length(mer) ) /*find maximum length of three numbers.*/
say indent center(' ',w1) center("sun hour",w2) center('dial hour' ,w3)▼
say indent center('hour',w1) center("angle" ,w2) center('line angle',w3)▼
▲ say indent center(' ', w1) center("sun hour", w2) center('dial hour' , w3)
▲ say indent center('hour', w1) center("angle" , w2) center('line angle', w3)
call sep /*to help a one-eyed pirate's eyeball. */
do h=-6 to 6 /*Okey dokey then, now let's show stuff*/
select
when abs(h)==12 then hc='midnight' /*Holy smokes! Above the arctic circle.*/
when h <0 then hc= -h 'am'
when h==0 then hc='noon' /* ··· easier to understand now. */
when h >0 then hc= h 'pm'
end /*select*/
hra=15 * h - lng + mer /*calculate sun hour angle (in degrees)*/
hla=r2d( Atan(sineLat * tan( d2r(hra))))
say indent center(hc, w1) right(format(hra, ,1), w2) right(format(hla, ,1), w3)
end /*h*/
call sep /*to help a one-eyed pirate's eyeball. */
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
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r2d: return d2d( (arg(1) * 180 / pi() ) ) /*convert radians ──► degrees. */
r2r: return arg(1) //(pi() * 2) /*normalize radians ──► a unit circle. */
sep: say indent copies('═', w1) copies("═", w2) copies('═', w3);
tan: procedure; parse arg x; _=cos(x); if _=0 then call tanErr; return sin(x)/_
tellErr: say; say '*** error ***'; say; say arg(1); say; exit 13
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tanErr: call tellErr 'tan(' || x") causes division by zero, X=" x
Acos: procedure; arg x; if x<-1 | x>1 then call AcosErr; return .5 * pi() - Asin(x)
Atan: procedure; parse arg x; if abs(x)=1 then return pi()/4*x; return Asin(x/sqrt(1+x*x))
/*──────────────────────────────────────────────────────────────────────────────────────*/
Asin: procedure;
if abs(x)>=sqrt(2)*.4 then return sign(x) * Acos(sqrt(1-s)); z=x; o=x; p=z
do j=2 by 2; o=o*s*(j-1)/j; z=z+o/(j+1); if z=p then leave; p=z; end; return z
/*──────────────────────────────────────────────────────────────────────────────────────*/
if abs(x)=pi() then return ;
/*──────────────────────────────────────────────────────────────────────────────────────*/
cos: procedure; parse arg x; x=r2r(x); a=abs(x); hpi=pi*.5
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if a=pi() * 2 / 3 then return -.5; return .sinCos(1,1,-1)
/*──────────────────────────────────────────────────────────────────────────────────────*/
.sinCos: parse arg z,_,i; x=x*x;
do k=2 by 2; _= -_
/*──────────────────────────────────────────────────────────────────────────────────────*/
sqrt: procedure; parse arg x; if x=0 then return 0; d=digits(); numeric digits; h=d+6
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