My while-loop in Swift won't terminate, what am i missing? - ios

Question

I have a pretty detailed while-loop and have been really resisting having to ask for help once again but I am at a loss! I really apologize for this while-loop code, there's a lot going on but I don't want to leave anything out just in case you viewers require to see it all.
func retRhoCurrent() -> Double {
while abs(pTarget - pCalc) > 1 {
//
// SET rhoCurrent
//
if (pTarget > pCalc) {
rhoLow = rhoCurrent
if(rhoCurrent >= rhoHigh) {
rhoCurrent += RHO_C
rhoHigh = rhoCurrent
} else {
rhoCurrent += ((rhoHigh - rhoCurrent)/2)
}
} else {
rhoHigh = rhoCurrent
rhoCurrent += ((rhoLow - rhoCurrent)/2)
}
//
// SET rhoR
//
rhoR = rhoCurrent / RHO_C
//
// SET DIFFERENTIAL
//
diffAggregate = 0
for var kIndex = 0; kIndex < NK_VALUES.count; ++kIndex {
diffSegment = NK_VALUES[kIndex]
diffSegment *= pow(rhoR, IK_VALUES[kIndex])
diffSegment *= pow(tempR, JK_VALUES[kIndex])
iFactor = 0
if LK_VALUES[kIndex] > 0 {
diffSegment *= exp(-1 * pow(rhoR, LK_VALUES[kIndex]))
iFactor = LK_VALUES[kIndex] * pow(rhoR, LK_VALUES[kIndex])
}
if PK_VALUES[kIndex] > 0 {
diffSegment *= exp(-1 * PK_VALUES[kIndex] * pow(rhoR, 2) - BK_VALUES[kIndex] * pow(tempR - UK_VALUES[kIndex], 2))
iFactor = 2 * rhoR * PK_VALUES[kIndex] * (rhoR - 1)
}
diffAggregate += (diffSegment * (IK_VALUES[kIndex] - iFactor))
}
//
// SET pCalc
//
zDiff + 1 + diffAggregate
pCalc = zDiff * R_CONST * 1000 * tempK * rhoCurrent
}
return rhoCurrent
}
I guess another question i have also is the main value I want out of this while loop is rhoCurrent (as I will use this final # to calculate something else). Doing the "return rhoCurrent" will work, correct?
Thanks so much in advance!!

Answer 1

I think you intended this line to assign a value, but it doesn't:
zDiff + 1 + diffAggregate
Because it doesn't assign a value, diffAggregate is not used in the body of your while loop. rhoR is also not used because of this. Your function can be simplified as such:
func retRhoCurrent() -> Double {
while abs(pTarget - pCalc) > 1 {
//
// SET rhoCurrent
//
if (pTarget > pCalc) {
rhoLow = rhoCurrent
if(rhoCurrent >= rhoHigh) {
rhoCurrent += RHO_C
rhoHigh = rhoCurrent
} else {
rhoCurrent += ((rhoHigh - rhoCurrent)/2)
}
} else {
rhoHigh = rhoCurrent
rhoCurrent += ((rhoLow - rhoCurrent)/2)
}
//
// SET pCalc
//
pCalc = zDiff * R_CONST * 1000 * tempK * rhoCurrent
}
return rhoCurrent
}
I'm really suspicious of the variables that you use in the loop but do not initialize within the function. What are the initial values for rhoLow, rhoHigh, rhoCurrent, tempK, zDiff, pTarget, and pCalc?
This method is very messy and depends on a lot of magic. It is modifying values that it does not own, meaning you could experience unexpected things in other areas of your app. It is definitely not thread-safe (though this may not be a concern for you).