# Errors ### List of errors #### Attempt to call a nil value Description: calling a function that doesn't exist Example: ```lua printtt("abc") -- printtt is not a function test() -- calling before it's defined, same error function test() end test() -- works ``` #### Unexpected symbol near 'something' Description: an invalid character is placed next to a value/keyword/variable/function call ```lua function abc()) end -- unexpected symbol near ')' local a = 5 a l= 15 -- unexpected symbol near 'l' local a = 5] -- unexpected symbol near ']' ``` #### Attempt to index global 'variable' (a nil value) Description: indexing via `[key]` or `.key` for a variable that doesn't exist Example: ```lua abc.x = 5 -- abc is nil, error abc = {} -- abc defined here abc.x = 5 -- works xyz['x'] = 'abc' -- xyz is nil, error ``` #### Attempt to perform arithmetic on a nil value Description: performing arithmetic (\*, /, -, +, %, ^) on a nil value Example: ```lua print(xyz + 5) -- error, xyz not defined a = a + 5 -- error, a not defined ``` #### Attempt to perform arithmetic on field '?' (a nil value) Description: performing arithmetic (\*, /, -, +, %, ^) on a nil value Example: ```lua local t = {} t.x = t.x + 5 ``` #### Attempt to compare nil with \ Description: using a comparison operator (<, >, \~=, ==, >=, <=) in which one side is a nil value Example: ```lua local x = 5 print(x < y) -- y is not defined ``` #### Malformed number near \ Description: the number has an invalid character next to it Example: ```lua print(12345aaa) -- aaa makes it a malformed number ``` #### Unfinished capture | Malformed pattern Description: the pattern is missing a closing `)`, or a closing `]` Example: ```lua print(string.match('ABC', '(')) -- unfinished capture print(string.match('ABC', '[')) -- malformed pattern ``` ### Interpreting errors When you get an error, Lua provides a stack trace showing you where it originates from, where the error occurs, the function calls that led to the error, and the line number of where it occurred. A general error will look like this: ``` file_location:LINE NUMBER: error message stack traceback: file_location:LINE NUMBER: in 'FUNC' file_location:LINE NUMBER: in main chunk [C]: in ? ``` Here's an example: ``` C:\Users\user\lua_file.lua:5: attempt to perform arithmetic on a nil value (field 'x') stack traceback: C:\Users\user\lua_file.lua:5: in local 'c' C:\Users\user\lua_file.lua:7: in local 'b' C:\Users\user\lua_file.lua:9: in function 'a' C:\Users\user\lua_file.lua:12: in main chunk [C]: in ? ``` The code that resulted in this error is: ```lua function a() local function b() local function c() local t = {} t.x = t.x + 5 end c() end b() end a() ``` Here you can see the line number `5` after the file location, which tells us where the exact line with the code that resulted in the error. The stack traceback shows the functions that were called that led up to that. First, function `a` is called at line 12, then function `b` is called at line 9 inside of `a`, then `c` is called at line 7 inside of function `b`, and finally at line 5, the error occurs inside of function `c`. A note to add is that comments can offset the line number and make it appear as the error is in a line that doesn't exist or doesn't look like an error, --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://stigmax.gitbook.io/lua-guide/auxiliary/errors.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.