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lander.js
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lander.js
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// C-FOCAL,1969
function *lunarLander(out) {
// full program as objects containing line numbers, remarks, functions
let code = []
// program counter (array index into code)
let pc = 0
// map of line number to code array index
let lines = {}
// The % operator
let fmt = {
// total number of digits to display
total: 8,
// places after decimal point
places: 4
}
// external process sets this value when input is required from
// the user
let result = {
input: ''
};
// number of lines executed (for help in stopping infinite loops early)
let exec = 0
// set to true after initializing via query string
let init = false
// set to true when it is time to terminate the program
let done = false
// add a line to the program with line number, 'num', the original
// source in the remark, 'rem', and the function 'fn', to execute.
function line(num, rem, fn) {
lines[num] = code.length
code.push({ num, rem, fn })
}
// FOCAL DO command. Execute block of code from the line number starting
// with 'start' and ending with 'end'. FOCAL doesn't have an end, this
// is here due to pure laziness as it is easier to implement.
function* do_(start, end) {
let prev = pc
goto_(start)
while (!done) {
let op = code[pc]
let execLineNum = op.num
if (exec > 10000) {
throw new Error(`execution limit exceeded: ${JSON.stringify(op, null, 2)}`)
}
debug()
console.log(`${op.num} ${op.rem}`)
exec++
pc++
yield* op.fn()
if (execLineNum === end) {
pc = prev
break
}
}
}
// FOCAL FITR function: the integer part function outputs the integer
// part of a number up to 2046
function fitr(x) {
return Math.trunc(x)
}
// FOCAL FSQRT function: Square root
function fsqrt(x) {
return Math.sqrt(x)
}
// FOCAL GOTO statement
function goto_(num) {
if (!(num in lines)) {
throw new Error(`no such line: ${num}`)
}
pc = lines[num]
}
// FOCAL TYPE statement. Only intended for numeric values that need
// to have formatting applied
function type(v) {
let s = v.toFixed(fmt.places)
out.print(s.toString().padStart(fmt.total + 1, " "))
}
// From https://www.cs.brandeis.edu/~storer/LunarLander/LunarLanderTranslations/LunarLanderJohnsonTranslation-c.txt
// Global variables
//
// A - Altitude (miles)
// G - Gravity
// I - Intermediate altitude (miles)
// J - Intermediate velocity (miles/sec)
// K - Fuel rate (lbs/sec)
// L - Elapsed time (sec)
// M - Total weight (lbs)
// N - Empty weight (lbs, Note: M - N is remaining fuel weight)
// S - Time elapsed in current 10-second turn (sec)
// T - Time remaining in current 10-second turn (sec)
// V - Downward speed (miles/sec)
// W - Temporary working variable
// Z - Thrust per pound of fuel burned
let a = 0
let g = 0
let i = 0
let j = 0
let k = 0
let l = 0
let m = 0
let n = 0
let p = '' // try again result
let s = 0
let t = 0
let v = 0
let w = 0
let z = 0
function debug() {
let vars = {a, g, i, j, k, l, m, n, s, t, v, z}
console.log(JSON.stringify(vars, null, 2))
}
line(
"01.04",
'T "CONTROL CALLING LUNAR MODULE. MANUAL CONTROL IS NECESSARY"!',
function* () {
out.println("CONTROL CALLING LUNAR MODULE. MANUAL CONTROL IS NECESSARY")
}
)
line(
"01.06",
'T "YOU MAY RESET FUEL RATE K EACH 10 SECS TO 0 OR ANY VALUE"!',
function* () {
out.println("YOU MAY RESET FUEL RATE K EACH 10 SECS TO 0 OR ANY VALUE")
}
)
line(
"01.08",
'T "BETWEEN 8 & 200 LBS/SEC. YOU\'VE 16000 LBS FUEL. ESTIMATED"!',
function* () {
out.println("BETWEEN 8 & 200 LBS/SEC. YOU'VE 16000 LBS FUEL. ESTIMATED")
}
)
line(
"01.11",
'T "FREE FALL IMPACT TIME-120 SECS. CAPSULE WEIGHT-32500 LBS"!',
function* () {
out.println("FREE FALL IMPACT TIME-120 SECS. CAPSULE WEIGHT-32500 LBS")
}
)
line(
"01.20",
'T "FIRST RADAR CHECK COMING UP"!!!;E',
function* () {
out.println("FIRST RADAR CHECK COMING UP")
out.println()
out.println()
}
)
line(
"01.30",
'T "COMMENCE LANDING PROCEDURE"!"TIME,SECS ALTITUDE,"',
function* () {
out.println("COMMENCE LANDING PROCEDURE")
out.print("TIME,SECS ALTITUDE,")
}
)
line(
"01.40",
'T "MILES+FEET VELOCITY,MPH FUEL,LBS FUEL RATE"!',
function* () {
out.println("MILES+FEET VELOCITY,MPH FUEL,LBS FUEL RATE")
}
)
line(
"01.50",
'S A=120;S V=1;S M=32500;S N=16500;S G=.001;S Z=1.8',
function* () {
a = 120
v = 1
m = 32500
n = 16500
g = .001
z = 1.8
// Variables assumed to be zero do not seem to get initialized
// when the game is replayed.
l = 0
// Initialize with query string if provided
if (!init) {
let params = new URLSearchParams(window.location.search);
let pa = params.get("a")
if (pa) {
a = Number.parseFloat(pa)
}
let pl = params.get("l")
if (pl) {
l = Number.parseFloat(pl)
}
let pf = params.get("f")
if (pf) {
m = 16500 + Number.parseFloat(pf)
}
let pv = params.get("v")
if (pv) {
v = Number.parseFloat(pv) / 3600
}
}
init = true
}
)
line(
"02.10",
'T " "%3,L," "FITR(A)," "%4,5280*(A-FITR(A))"',
function* () {
out.print(" ")
fmt.total = 3
fmt.places = 0
type(l)
out.print(" ")
type(fitr(a))
out.print(" ")
fmt.total = 4
type(5280 * (a - fitr(a)))
}
)
line(
"02.20",
'T %6.02," ",3600*V," ",%6.01,M-N," K=";A K;S T=10',
function* () {
fmt.total = 6
fmt.places = 2
out.print(" ")
type(3600 * v)
out.print(" ")
fmt.total = 6
fmt.places = 1
type(m - n)
out.print(" K=:")
yield result
k = Number.parseFloat(result.input)
t = 10
}
)
line(
"02.70",
'T %7.02;I (200-K)2.72;I (8-K)3.1,3.1;I (K)2.72,3.1',
function* () {
fmt.total = 7
fmt.places = 2
if (200 - k < 0) {
goto_("02.72")
} else if (8 - k <= 0 ) {
goto_("03.10")
} else if ( k < 0 ) {
goto_("02.72")
} else if ( k == 0 ) {
goto_("03.10")
}
}
)
line(
"02.72",
'T "NOT POSSIBLE";F X=1,51;T "."',
function* () {
out.print('NOT POSSIBLE')
for (x = 1; x <= 51; x++) {
out.print('.')
}
}
)
line(
"02.73",
'T "K=";A K;G 2.7"',
function* () {
out.print("K=:")
yield result
k = Number.parseFloat(result.input)
goto_("02.70")
}
)
line(
"03.10",
'I (M-N-.001)4.1;I (T-.001)2.1;S S=T',
function* () {
if (m-n-.001 < 0) {
goto_("04.10")
} else if (t-.001 < 0) {
goto_("02.10")
} else {
s = t
}
}
)
line(
"03.40",
'I ((N+S*K)-M)3.5,3.5;S S=(M-N)/K',
function* () {
if ((n+s*k)-m <= 0) {
goto_("03.50")
} else {
s = (m-n)/k
}
}
)
line(
"03.50",
'D 9;I (I)7.1,7.1;I (V)3.8,3.8;I (J)8.1',
function* () {
yield* do_("09.10", "09.40")
if (i <= 0) {
goto_("07.10")
} else if (v <= 0) {
goto_("03.80")
} else if (j < 0) {
goto_("08.10")
}
}
)
line(
"03.80",
'D 6;G 3.1',
function* () {
yield* do_("06.10", "06.10")
goto_("03.10")
}
)
line(
"04.10",
'T "FUEL OUT AT",L," SECS"!',
function* () {
out.print("FUEL OUT AT")
type(l)
out.println(" SECS")
}
)
line(
"04.40",
'S S=(FSQT(V*V+2*A*G)-V)/G;S V=V+G*S;S L=L+S',
function* () {
s = (fsqrt(v*v+2*a*g)-v)/g
v = v+g*s
l = l+s
}
)
line(
"05.10",
'T "ON THE MOON AT",L," SECS"!;S W=3600*V',
function* () {
out.print("ON THE MOON AT")
type(l)
out.println(" SECS")
w = 3600*v
}
)
line(
"05.20",
'T "IMPACT VELOCITY OF"W," M.P.H."!"FUEL LEFT:"M-N," LBS"!',
function* () {
out.print("IMPACT VELOCITY OF")
type(w)
out.println(" M.P.H.")
out.print("FUEL LEFT:")
let f = m-n
// Is there ever a check to see if fuel is below zero?
if (f < 0) {
f = 0
}
type(f)
out.println(" LBS")
}
)
line(
"05.40",
'I (1-W)5.5,5.5;T "PERFECT LANDING !-(LUCKY)"!;G 5.9',
function* () {
if (1-w <= 0) {
goto_("05.50")
} else {
out.println("PERFECT LANDING !-(LUCKY)")
goto_("05.90")
}
}
)
line(
"05.50",
'I (10-W)5.6,5.6;T "GOOD LANDING-(COULD BE BETTER)";G 5.9',
function* () {
if (10-w <= 0) {
goto_("05.60")
} else {
out.println("GOOD LANDING-(COULD BE BETTER)")
goto_("05.90")
}
}
)
line(
"05.60",
'I (22-W)5.7,5.7;T "CONGRATULATIONS ON A POOR LANDING";G 5.9',
function* () {
if (22-w <= 0) {
goto_("05.70")
} else {
out.println("CONGRATULATIONS ON A POOR LANDING")
goto_("05.90")
}
}
)
line(
"05.70",
'I (40-W)5.81,5.81;T "CRAFT DAMAGE. GOOD LUCK";G 5.9',
function* () {
if (40-w <= 0) {
goto_("05.81")
} else {
out.println("CRAFT DAMAGE. GOOD LUCK")
goto_("05.90")
}
}
)
line(
"05.81",
'I (60-W)5.82,5.82;T "CRASH LANDING-YOU\'VE 5 HRS OXYGEN";G 5.9',
function* () {
if (60-w <= 0) {
goto_("05.82")
} else {
out.println("CRASH LANDING-YOU\'VE 5 HRS OXYGEN")
goto_("05.90")
}
}
)
line(
"05.82",
'T "SORRY,BUT THERE WERE NO SURVIVORS-YOU BLEW IT!"!"IN "',
function* () {
out.println("SORRY,BUT THERE WERE NO SURVIVORS-YOU BLEW IT!")
out.print("IN ")
}
)
line(
"05.83",
'T "FACT YOU BLASTED A NEW LUNAR CRATER"W*.277777," FT. DEEP"!',
function* () {
out.print("FACT YOU BLASTED A NEW LUNAR CRATER")
type(w*.277777)
out.println(" FT. DEEP")
}
)
line(
"05.90",
'T !!!!"TRY AGAIN?"!',
function* () {
out.println()
out.println()
out.println()
out.println()
out.println("TRY AGAIN?")
}
)
line(
"05.92",
'A "(ANS. YES OR NO)"P;I (P-0NO)5.94,5.98',
function* () {
out.print("(ANS. YES OR NO):")
yield result
p = result.input.toUpperCase()
if (p === 'NO') {
goto_("05.98")
} else {
goto_("05.94")
}
}
)
line(
"05.94",
'I (P-0YES)5.92,1.2,5.92',
function* () {
if (p === 'YES') {
goto_("01.20")
} else {
goto_("05.92")
}
}
)
line(
"05.98",
'T "CONTROL OUT"!!!;Q',
function* () {
out.println("CONTROL OUT")
out.println()
out.println()
done = true
}
)
line(
"06.10",
'S L=L+S;S T=T-S;S M=M-S*K;S A=I;S V=J',
function* () {
l = l+s
t = t-s
m = m-s*k
a = i
v = j
}
)
line(
"07.10",
'I (S-.005)5.1;S S=2*A/(V+FSQT(V*V+2*A*(G-Z*K/M)))',
function* () {
if (s-.005 < 0) {
goto_("05.10")
} else {
s = 2*a/(v+fsqrt(v*v+2*a*(g-z*k/m)))
}
}
)
line(
"07.30",
'D 9;D 6;G 7.1',
function* () {
yield* do_("09.10", "09.40")
yield* do_("06.10", "06.10")
goto_("07.10")
}
)
// From: https://www.cs.brandeis.edu/~storer/LunarLander/LunarLanderTranslations/LunarLanderJohnsonTranslation-c.txt
// FOCAL-to-C gotcha: In FOCAL, multiplication has a higher
// precedence than division. In C, they have the same
// precedence and are evaluated left-to-right. So the
// original FOCAL subexpression `M * G / Z * K` can't be
// copied as-is into C: `Z * K` has to be parenthesized to
// get the same result.
line(
"08.10",
'S W=(1-M*G/(Z*K))/2;S S=M*V/(Z*K*(W+FSQT(W*W+V/Z)))+.05;D 9',
function* () {
w = (1-m*g/(z*k))/2;
s = m*v/(z*k*(w+fsqrt(w*w+v/z)))+ 0.5;
yield* do_("09.10", "09.40")
}
)
line(
"08.30",
'I (I)7.1,7.1;D 6;I (-J)3.1,3.1;I (V)3.1,3.1,8.1',
function* () {
if (i <= 0) {
goto_("07.10")
} else {
yield* do_("06.10", "06.10")
if (-j <= 0) {
goto_("03.10")
} else if (v <= 0) {
goto_("03.10")
} else {
goto_("08.10")
}
}
}
)
line(
"09.10",
'S Q=S*K/M;S J=V+G*S+Z*(-Q-Q^2/2-Q^3/3-Q^4/4-Q^5/5)',
function* () {
q = s*k/m
let q2 = Math.pow(q, 2)
let q3 = Math.pow(q, 3)
let q4 = Math.pow(q, 4)
let q5 = Math.pow(q, 5)
j=v+g*s+z*(-q-q2/2-q3/3-q4/4-q5/5)
}
)
line(
"09.40",
'S I=A-G*S*S/2-V*S+Z*S*(Q/2+Q^2/6+Q^3/12+Q^4/20+Q^5/30)',
function* () {
let q2 = Math.pow(q, 2)
let q3 = Math.pow(q, 3)
let q4 = Math.pow(q, 4)
let q5 = Math.pow(q, 5)
i = a-g*s*s/2-v*s+z*s*(q/2+q2/6+q3/12+q4/20+q5/30)
}
)
yield* do_("01.04")
return
}