Attempt to call a string value. error doesn't happen on first call

Hello World

I'm working on building an intro to programming curriculum with computer craft aimed at kids grades 1-3. I have a system where they don't directly deal with the shell until a later lesson, to keep them focus on coding and avoid confusion. it's also set up(in other code) for them to edit on a computer which sends the programs to the turtle over rednet. Right now i have a file menu system, when they create a new program it copies a template and opens it for editing. Everything works, except the copy function. it works once, and everything else works after you use it once. if you enter copy again i get

101:attempt to call string

i don't see and missing ..'s and it did work the first time.

function edit()
 local input="42"
 while true do
  valid=false
  while not valid do
 term.clear()
 term.setCursorPos(1,1)
 print("Program Editor")
 print("")
   list = fs.list("turtle")
    if #list==0 then
     print("No Programs Created Yet. Hit enter.")
     io.read()
     return
    end
   print([[Enter the name of the program you'd like to edit or x to exit then hit enter.
   ]])
   while not valid do
    list = fs.list("turtle")
    textutils.pagedTabulate(list)
    print("")
    input = tostring(io.read())
    for i=1, #list do
     if list[i] == input then valid = true break end
    end
    if not valid and input~="x" and input~="42" then
      print(input.." does not exist. Please check for typos and try again or type x to exit.")
    elseif input=="x" then
     return  
    end
   end
  end
  shell.run("fg edit turtle/"..input)
 end
 return
end

function copy()
 local input = "42"
 list = fs.list("turtle")
  while true do
   valid=false
   while not valid do
    term.clear()
    term.setCursorPos(1,1)
    print("Program Copier")
    print("")
   while not valid do
    list = fs.list("turtle")
    textutils.pagedTabulate(list)
    print("")
    input = tostring(io.read())
    for i=1, #list do
     if list[i] == input then valid = true break end
    end
    if not valid and input~="x" and input~="42" then
      print(input.." does not exist. Please check for typos and try again or type x to exit.")
    elseif input=="x" then
     return  
    end
   end
  print("What will you name this copy of "..input.."?")
  copy =tostring(io.read())
  fs.copy("turtle/"..input,"turtle/"..copy)
  end
  print("Opening "..copy.." for editing in a new tab.")
  sleep(1.6)
  shell.run("fg edit turtle/"..copy)
  return
 end
end

function new()
 term.clear()
 term.setCursorPos(1,1)
 print("Create New Program From Template.")
 print("")
 print("Enter a name for this new program. Do not use spaces.")
 input = io.read()
 while fs.exists("turtle/"..input) and input~="x" do
  print(input.." alio.ready exists. Enter a different name or enter x to exit")
 local input = io.read()
 end
 fs.copy("template", "turtle/"..input)
 shell.run("fg edit turtle/"..input)
 return
end

while true do
 term.clear()
 term.setCursorPos(1,1)
 print("Main Menu")
 print("")
 print("Enter edit, copy or new to edit, copy or create a new program.")
 local input = io.read()
 while input ~= "edit" and input ~= "copy" and input ~= "new" and input ~= "shell" do
  print(input.." is not a valid command.")
  input = io.read()
 end
 if input == "edit" then edit()
 elseif input == "copy" then copy()
 elseif input == "new" then new() 
 elseif input == "shell" then shell.run("fg shell") 
 end
end

You overwrite the copy function with a string within itself

  copy =tostring(io.read())

Use local variables.

i haven't programmed since TI basic in high school and I'm relearning to develop this, would you mind elaborating? i understand local variables but does that mean my check will be

 input = tostring(io.read())
 end
 if input == "edit" then edit()
 elseif input == "copy" then copy()
 elseif input == "new" then new() 

?

i'll have to test that later, thanks for replying.

errr no, it does not. You store your copy function in the variable "copy", however when you run it you overwrite the function stored in "copy" with a string, in the line i posted. Changing the copy variable defined within the function to local, would prevent it from overwriting the function variable which is defined globally.

thanks, now i understand. I changed the internal copy variable to a local variable copyName.