Move from the current position the file is at. Set to start from the beginning of the file. This has the following starting points: set Seek works the same in 5.1, 5.2, and 5.3. Let’s do the same with Lua 5.3: #!/usr/bin/lua5.3 Let’s see all of our options smashed together now that we’ve seen the basic structure: #!/usr/bin/lua5.1 We’re going to start the whole file over and over again to avoid any issues. Let’s try each of our options out for reading and see what we get. (Note the new line at the end of test.txt) Let’s see it all in action with test.txt: 123 These basically all return nil if there isn’t a valid sequence, except for the “all” options which return an empty string as long as the file is valid. Reads a single line from the file, but keeps the end of line character(s) Lua 5.3 is adds the following (but is backwards compatible): a This reads until the end of a valid sequence. The options correspond to the following table for Lua 5.1 and 5.2: *line Reading is done via: filehandle:read( "" ] ) Once you open your file, you can read it. local filehandle = io.open( "mycontents.txt", "rb" ) Once you’re done with a file, you need to close it. When working with opening files, you should assign the file handle to a variable to do anything useful. You can also use the b modifier at the end of the mode in order to open the file in binary mode. Repositioning operations affect read mode. Clears existing contents or makes a new file.Īppend the file with read mode. Overwrites contents or makes a new file.Īppend the file. The filename is where the file is, and the mode is listed in the table below (or following the same mode as in C for fopen).
The # operator will only count those keys, ignoring any others present. The sequence part only consists of all numbered keys starting from 1 ascending up to the last key with a non-nil value. However, those keys are not considered part of the sequence.
Note that a table containing a sequence is also allowed to have other keys. To avoid this problem, only make changes at the end of a sequence. There seems to be no consistent behavior. In some cases, Lua will recognize the change and will adjust the sequence. add three more elements to the sequenceĬaution: If a key other than the final key is set to nil, or a key other than the next after the sequence is set to non-nil, the result is undefined. Similarly, setting the next key to something non-nil will extend the sequence by 1, and this should always be done in forward order. Setting the final key(s) to nil is okay, because Lua will understand that they are being removed, and it will therefore reduce the length by by that many. Only contiguous keys at the end of the sequence should be cleared, in reverse order. No key in the middle of a sequence should ever be set/cleared to nil. Print("p is nil") - should print "p is nil" Lua offers special syntax and features so that sequences behave somewhat like lists or arrays in other languages.
#Lua table insert append series#
PICO-8 provides the built-in pairs(), which iterates over all key-value pairs in a table.Ī sequence is a table with a contiguous series of numeric keys, starting with 1, each of which has a non-nil value. If the key is a string using the characters of a Lua identifier (letters, numbers, underscore, and begins with a letter), then the value can also be accessed using property notation ( tbl.key). Values can be accessed using bracket notation, where the key is an expression ( tbl). You can construct a new mapping using curly brackets. PICO-8 includes several built-in functions for using tables.įundamentally, tables are mappings of keys to values. Tables can be used as general purpose objects, and when combined with metatables (see Lua reference) can implement object-oriented concepts such as inheritance. They are used as containers, especially sequences (with consecutive numeric indexes starting from 1) and mappings (also known as associative arrays, dictionaries, or hashtables). Tables are the primary composite data structure in the Lua programming language.
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