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Étienne Fildadut 2021-06-11 14:29:12 +02:00
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@ -461,11 +461,13 @@ The preprocessor has access to the following variables:
#### Macros #### Macros
Using `define(identifier, replacement)` in the preprocessor, you can define macros. Both identifier and replacement are expected to be string containing Candran/Lua code. Using `define(identifier, replacement)` in the preprocessor, you can define macros. `identifier` is expected to be string containing Candran/Lua code (representing either a identifier or a function call), and `replacement` can be either a string containing Candran/Lua code or a function.
There are two types of macros: variables, which replace every instance of the given identifier with the replacement text; and functions, which will replace every call to this function with the replacement text, also replacing its arguments. The `...` will be replaced with every remaining argument. Macros can not be recursive. There are two types of macros identifiers: variables, which replace every instance of the given identifier with the replacement; and functions, which will replace every call to this function with the replacement, also replacing its arguments. The `...` will be replaced with every remaining argument. Macros can not be recursive.
If the replacement text is empty, the macro will simply be removed from the compiled code. If `replacement` is a string, the macro will be replaced with this string, replacing the macros arguments in the string. If `replacement` is a function, the function will be called every time the macro is encoutered, with the macro arguments passed as strings, and is expected to return a string that will be used as a replacement.
If `replacement` is the empty empty, the macro will simply be removed from the compiled code.
```lua ```lua
-- Variable macro -- Variable macro
@ -481,8 +483,17 @@ log("network", "error") -- network: error
#define("debug()", "") #define("debug()", "")
debug() -- not present in complied code debug() -- not present in complied code
#define("_assert(what, err)", function(what, err)
# return "if "..what.." then error("..err..") end"
#end)
_assert(5 = 2, "failed") -- replaced with if 5 = 2 then error("failed") end
``` ```
Candran provide some predefined macros by default:
* `__STR__(expr)`: returns a string litteral representing the expression (e.g., `__STR__(5 + 2)` expands to `"5 + 2"`)
* `constexpr(expr)`: calculate the result of the expression in the preprocessor, and returns a representation of the returned value, i.e. precalculate an expression at compile time
Compile targets Compile targets
--------------- ---------------
Candran is based on the Lua 5.4 syntax, but can be compiled to Lua 5.4, Lua 5.3, Lua 5.2, LuaJIT, and Lua 5.1 compatible code. Candran is based on the Lua 5.4 syntax, but can be compiled to Lua 5.4, Lua 5.3, Lua 5.2, LuaJIT, and Lua 5.1 compatible code.