After two years of development, on June 29, the new version of the Lua programming language \u2013 5.4 \u2013 was quietly released.<\/p>\n
Lua is a simple interpreted programming language that is easy to embed in applications. Due to these features, Lua is widely used as a scripting language or configuration description for programs (especially computer games). Lua is distributed under the MIT license.<\/p>\n
The previous version (5.3.5) was released on July 10, 2018.<\/p>\n
Key changes in the new version<\/h2>\n
\n
\n
a new generational garbage collector. The parameters setpause and setstepmul in the collectgarbage function are deprecated; it is recommended to use the incremental parameter instead;<\/p>\n<\/li>\n
\n
a new function for issuing warnings warn with the ability to disable their display;<\/p>\n<\/li>\n
\n
the new implementation of math.random uses the xoshiro256** algorithm instead of the provided libc and initializes the generator with a random number;<\/p>\n<\/li>\n
\n
constant variables;<\/p>\n<\/li>\n
\n
\"To-be-closed\" variables are local constants for which the __close method is executed when exiting the scope;<\/p>\n<\/li>\n<\/ul>\n
\n
\n
a new function lua_resetthread \u2013 clears the stack and closes all to-be-closed variables;<\/p>\n<\/li>\n
\n
a new function coroutine.close \u2013 closes the specified coroutine and all its to-be-closed variables;<\/p>\n<\/li>\n
\n
userdata can contain a set of values accessible by index. New functions have been introduced for working with them: lua_newuserdatauv, lua_setiuservalue, and lua_getiuservalue;<\/p>\n<\/li>\n
\n
debugging information about function parameters and return values is available;<\/p>\n<\/li>\n
\n
if an integer index is used in a for loop and overflow occurs, the loop terminates;<\/p>\n<\/li>\n
\n
an optional argument has been added to the string.gmatch function to specify an offset from the start of the string for finding matches;<\/p>\n<\/li>\n
\n
Implicit conversion functions from strings to numbers have been moved to the string library, and their behavior has changed. For example, the result of the operation \"1\" + \"2\" is now an integer instead of a floating-point number;<\/p>\n<\/li>\n
\n
an error may occur in the memory allocation function when reducing the memory block;<\/p>\n<\/li>\n
\n
A new formatting symbol in the string.format function is %p (for pointers);<\/p>\n<\/li>\n
\n
the utf8 library accepts character codes up to 2\u00b3\u00b9 (when a special flag is specified, without it only codes up to 0x10FFFF are allowed and surrogates are not permitted);<\/p>\n<\/li>\n
\n
Integer constants that exceed the value range are converted to floating-point numbers (previously, this resulted in bit truncation);<\/p>\n<\/li>\n
\n
The __lt metamethod is no longer used to emulate the __le metamethod; if necessary, the __le metamethod must be explicitly set;<\/p>\n<\/li>\n
\n
A label for the goto statement cannot be created if a label with the same name already exists in the current scope (even if it was defined in an outer scope);<\/p>\n<\/li>\n
\n
The __gc metamethod can be more than just a function. If calling the method fails, a warning will be issued;<\/p>\n<\/li>\n
\n
The print function does not call tostring for each argument but uses its internal conversions;<\/p>\n<\/li>\n
\n
The io.lines function returns a set of four values instead of one; to emulate the old behavior, enclose the call in parentheses if substituting it as a parameter in another function call.<\/p>\n<\/li>\n<\/ul>\n