Pastebin.com is the number one paste tool since 2002. Pastebin is a website where you can store text online for a set period of time. CSharp.lua is a C# to Lua compiler. Write C# then run on lua VM. Build on Microsoft Roslyn. Support for C# 8.0.

Solved: It is possible to call C/C code from Lua and I wonder - is it allowed to do that in Lightroom plugins? Is it possible to ship a Lightroom plugin - 10550427. I found a formula few months ago, myself to translate any source language (computer characters) to destination (computer characters). Using Lua (desk top users) and C class (for native access) so that i can embed it in Web Browser etc etc. I am wondering if we have already better something for this in C or Lua. Posted May 28, 2015. It is possible to convert a part of a code in C for.lua? Share on other sites.

Remarks

Booleans, truth, and falsity are straightforward in Lua. To review:

There is a boolean type with exactly two values: true and false.
In a conditional context (if, elseif, while, until), a boolean is not required. Any expression can be used.
In a conditional context, false and nil count as false, and everything else counts as true.
Although 3 already implies this: if you're coming from other languages, remember that 0 and the empty string count as true in conditional contexts in Lua.

The boolean type

Booleans and other values

When dealing with lua it is important to differentiate between the boolean values true and false and values that evaluate to true or false.

There are only two values in lua that evaluate to false: nil and false, while everything else, including the numerical 0 evaluate to true.

Some examples of what this means:

Logical Operations

Logical operators in lua don't necessarily return boolean values:

and will return the second value if the first value evaluates to true;

or returns the second value if the first value evaluates to false;

This makes it possible to simulate the ternary operator, just like in other languages:

This can also be used to initialize tables if they don't exist

or to avoid using if statements, making the code easier to read

Checking if variables are defined

One can also easily check if a variable exists (if it is defined), since non-existant variables return nil, which evaluates to false.

The only case where this does not apply is when a variable stores the value false, in which case it technically exists but still evaluates to false. Because of this, it is a bad design to create functions which return false and nil depending on the state or input. We can still check however whether we have a nil or a false:

C++ To Lua Translator Free

Conditional contexts

Conditional contexts in Lua (if, elseif, while, until) do not require a boolean. Like many languages, any Lua value can appear in a condition. The rules for evaluation are simple:

false and nil count as false.
Everything else counts as true.

Logical Operators

In Lua, booleans can be manipulated through logical operators. These operators include not, and, and or.

In simple expressions, the results are fairly straightforward:

Order of Precedence

The order of precedence is similar to the math operators unary -, * and +:

not
then and
then or

This can lead to complex expressions:

Short-cut Evaluation

The operators and and or might only be evaluated using the first operand, provided the second is unnecessary:

Idiomatic conditional operator

Due to the precedence of the logical operators, the ability for short-cut evaluation and the evaluation of non-false and non-nil values as true, an idiomatic conditional operator is available in Lua:

Also, due to the nature of the x and a or b structure, a will never be returned if it evaluates to false, this conditional will then always return b no matter what x is.

C++ To Lua Translator Online

Truth tables

Logical operators in Lua don't 'return' boolean, but one of their arguments. Using nil for false and numbers for true, here's how they behave.

As you can see, Lua will always return the first value that makes the check fail or succeed. Here's the truth tables showing that.

For those who need it, here's two function representing these logical operators.

Emulating Ternary Operator with 'and' 'or' logical operators.

In lua, the logical operators and and or returns one of the operands as the result instead of a boolean result. As a consequence, this mechanism can be exploited to emulate the behavior of the ternary operator despite lua not having a 'real' ternary operator in the language.

Syntax

conditionandtruthy_exprorfalsey_expr

Use in variable assignment/initialization

Use in table constructor

Cula Translate

Use as function argument

Use in return statement

Caveat

C++ To Lua Converter

There are situations where this mechanism doesn't have the desired behavior. Consider this case

C++ To Lua Converter Online

In a 'real' ternary operator, the expected value of var is false. In lua, however, the and evaluation 'falls through' because the second operand is falsey. As a result var ends up with should not happen instead.

Two possible workarounds to this problem, refactor this expression so the middle operand isn't falsey. eg.

or alternatively, use the classical ifthenelse construct.

On Sat, Apr 3, 2010 at 12:35 AM, Vafa Khalighi <[hidden email]> wrote:
>> In what sense? Do you want to use your compiled C function in Lua, or do
>> you want to convert a C procedure into its equivalent in Lua? ...
> Thanks. I meant the latter.
If you want this in a general sense, see David Given's clue [1,2], but
it's said to be experimental, and I doubt your result will be pretty.
This might be analogous to what Alchemy/LLVM does [5].
I have found that C code can be translated into Lua code in a mostly
mechanical way if want to preserve structure over efficiency. Even
something like a pointer into a C array can be translated into an
index into a Lua table array. That was the case with Lua's lstrlib.c
translated into Lua [3], and it appears also with Yueliang [4]. You
can stumble with things like 'continue' statements, which Lua doesn't
directly support, so you may need to do some pre-translation
reworking.
[1] http://lua-users.org/lists/lua-l/2008-07/msg00114.html
[2] http://lua-users.org/wiki/LuaImplementations
[3] http://lua-users.org/wiki/StringLibraryInLua
[4] http://yueliang.luaforge.net/
[5] http://labs.adobe.com/technologies/alchemy/