The connection of data first needs to load a code block. If chunk is a string, the code block references the string. If chunk is a function, load will keep calling it to get fragments of code blocks. Every call to chunk must return a string immediately after the last call. When an empty string, nil or no value is returned, it indicates the end of the code block.
1. If there are no syntax errors, return the compiled code block as a function; ? Otherwise, return nil and an error message.
If the result function has an upper limit, env is set to the first upper limit. If this parameter is not provided, the global environment will replace it. All other upper limit values are initialized to zero. When you load the main code block, the result function must have one and only one upper value _ENV. However, if the binary code block created by the function is loaded (see string.dump, the resulting function can have any number of upper bounds), all the upper bounds are newly created. That is, they are not shared with any other functions.
The next step is to do the following things according to the above information. Chunkname is used as the name of the code block in error messages and debugging messages. If this parameter is not provided, it defaults to a string block. When chunk is not a string, it is "=(load)".
String mode is used to control whether a code block is text or binary (that is, a precompiled code block). It can be the string "b" (binary code block only), "t" (text code block only) or "bt" (binary or text). The default value is "bt".
3.Lua does not check the robustness of binary code blocks. ? Malicious construction of binary blocks may cause the interpreter to crash.
Run the program to traverse all fields in the table. The first parameter is the table to traverse, and the second parameter is a key in the table. Next returns the next key of the key and its associated value. Calling next with nil as the second parameter will return the initial key and its related values. When the last key is called, or an empty table is called with nil, next returns nil. If the second parameter is not provided, it will be treated as zero. In particular, you can use next(t) to determine whether a table is empty.
The index order in the traversal process is uncertain, even for numerical indexes. (If you want to traverse the table in numerical order, you can use the digital form of for. )
4. When you assign a value to a field that does not exist in the table during traversal? Next's behavior is undefined. ? However, you can modify these existing domains. In particular, you can clear some existing domains.
If t has a meta method __pairs, call it with t as a parameter and return the first three values it returns.
Otherwise, three values are returned: the next function, table t and nil. So the following code
Iteration represents all key-value pairs in T.
For the risk of modifying the table during iteration, see the function next.
pcall (f [，arg 1，])
5. The passed-in parameter calls the function f in protected mode. ? This means that any mistakes in f will not be thrown; ? Instead, pcall will catch the error and return a status code. The first return value is the status code (a Boolean quantity), which is true when there is no error. At this point, pcall will also return the results of all calls after the status code. When an error occurs, pcall returns false and an error message.
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