Error: Output argument "__" (and maybe others) not assigned during call to "__"

I wrote this simple code of a program that receives input from the user and calculates the parking bill following certain rules. The code includes two functions. I keep getting this error whenever the main function calls the second one:

Error in longTerm (line 2)
if mins<=60
Output argument "bill" (and maybe others) not assigned during call to "longTerm".

Error in assignment1q3 (line 15)
        bill = longTerm(mins);

This is the part of the main function (assignment1q3) where function (longTerm) is called:

switch(lot)
    case {'lt','LT'}
        bill = longTerm(mins);
    case {'st','ST'}
        bill = shortTerm(mins);
    otherwise
        disp('Invalid input')
end

this is the function called:

function bill = longTerm(mins)
if mins<=60
    bill = 1;
elseif mins<=1440 && mins>60
    bill = 1 + mins/60;
    if mins<=1440 && bill>6;
        bill = 6;
    elseif mins<=10080 && bill>42
        bill = 42;
    end
elseif mins>10080
    bill = 42;
end
end

I tried changing variable names of the functions but I still got the same error. What should I do?

Answer 1

[Star Strider]

Assign a default value for bill first. It will prevent that error and will also help you troubleshoot your code:

function bill = longTerm(mins)
bill = NaN;
if mins<=60
    . . . CODE  . . .
end

Answer 2

[Stephen23]

The problem is simple. In your function you define bill for each of these cases:

function bill = longTerm(mins)
if mins<=60
    ...
elseif mins<=1440 && mins>60
    ...
elseif mins>10080
    ...
end
end

But what happens when mins>1440 && min<=10080 ? In this case bill is not defined. The easiest solution would be to simply add an else case to the end of your if / elseif statements:

... your code
else
    bill = NaN;
end