A stack machine is a Turing Complete computer. Like any other machine, it uses an operating system to control its processes. For example the Burroughs B5000 was a stack machine and its instruction set defined a relatively high level programming language. Similarly, the interpreter for Adobe 's PostScript print formatting language is a virtual. Instead of storing values into variables, one passes them as arguments to functions. Example: abstract stack (functional) For example, a complete functional-style definition of an abstract stack could use the three operations: push: takes a stack state and an arbitrary value, returns a stack state; top: takes a stack state, returns a value. Local Variables Within If Statements; Short Circuit Logic; Introduction Every computer language has if statements. That's the main way to implement branching. Branching is the jumping to different code depending on some variable or condition. If Statement Basics Lua if statements are pretty simple. The simplest look like this.

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Programming in Lua

Part IV. The C APIChapter 24. An Overview of the C API

24.2.1 – Pushing Elements

Set Variable To Value On Stack Lua C++ Tutorial

The API has one push function for each Lua type thatcan be represented in C:lua_pushnil for the constant nil,lua_pushnumber for numbers (double),lua_pushboolean for booleans (integers, in C),lua_pushlstring for arbitrary strings (char *),and lua_pushstring for zero-terminated strings:There are also functions to push C functions and userdatavalues on the stack; we will discuss them later.

Strings in Lua are not zero-terminated;in consequence, they can contain arbitrary binary dataand rely on an explicit length.The official function to push a string ontothe stack is lua_pushlstring,which requires an explicit length as an argument.For zero-terminated strings, you can use also lua_pushstring,which uses strlen to supply the string length.Lua never keeps pointers to external strings(or to any other object, except to C functions,which are always static).For any string that it has to keep,Lua either makes an internal copy or reuses one.Therefore, you can free or modify your bufferas soon as these functions return.

Whenever you push an element onto the stack,it is your responsibility to ensure that the stack has space for it.Remember, you are a C programmer now; Lua will not spoil you.When Lua starts and any time that Lua calls C,the stack has at least 20 free slots(this constant is defined as LUA_MINSTACK in lua.h).This is more than enough for most common uses,so usually we do not even think about that.However, some tasks may need more stack space(e.g., for calling a function with a variable number of arguments).In such cases, you may want to callwhich checks whether the stack has enough space for your needs.(More about that later.)

24.2.1 – Pushing Elements

Set Variable To Value On Stack Lua C++ Tutorial

Set Variable To Value On Stack Lua C++ Code