When I analysis a cpp file using clang、clangAST，etc，what ever the function parameter type is，the result is int * type
how to get the real original type of function's parameter type in cpp file
I am using instructions from here on how to get started with open layers and I got the error: Namespace "ol" already declared - source ol-debug.js and the error
this.Va is not a function - source ol.js
I am pretty sure I have included the ol.js, ol-debug.js and ol.css files properly in my index.html.
Link to open layers js and css files.
This is the relevant part from ol-debug.js file -
/**
* Defines a namespace in Closure.
*
* A namespace may only be defined once in a codebase. It may be defined using
* goog.provide() or goog.module().
*
* The presence of one or more goog.provide() calls in a file indicates
* that the file defines the given objects/namespaces.
* Provided symbols must not be null or undefined.
*
* In addition, goog.provide() creates the object stubs for a namespace
* (for example, goog.provide("goog.foo.bar") will create the object
* goog.foo.bar if it does not already exist).
*
* Build tools also scan for provide/require/module statements
* to discern dependencies, build dependency files (see deps.js), etc.
*
* #see goog.require
* #see goog.module
* #param {string} name Namespace provided by this file in the form
* "goog.package.part".
*/
goog.provide = function(name) {
if (goog.isInModuleLoader_()) {
throw Error('goog.provide can not be used within a goog.module.');
}
if (!COMPILED) {
// Ensure that the same namespace isn't provided twice.
// A goog.module/goog.provide maps a goog.require to a specific file
if (goog.isProvided_(name)) {
throw Error('Namespace "' + name + '" already declared.');
}
}
goog.constructNamespace_(name);
};
You need to declare either ol.js or ol-debug.js, not both of them. The error is coming from the fact that you're declaring both of them and it is creating a namespace conflict.
I have a file with a module with some routines that take parameters and return unit, these routines have side-effects. I noticed that when accessing these f# routines from c# they're actually properties of type unit and when I try to access 1 property, it runs all properties in the module.
From the F# documentation all top level do bindings are run on type initialization.
What is the preferred way to write functions that should not be run on type initialization but are also not associated with other state i.e. a class with functions and member variables?
Should I put these functions inside a type and just have no records in the type?
Code example:
namespace test_space
open System.Diagnostics;
module test =
let test_1 =
Debug.WriteLine ("One")
let test_2 =
Debug.WriteLine ("Two")
I'm running this code with C#:
static void Main (string [] args)
{
Object o;
o = test.test_2;
}
And the output is:
One
Two
The problem is you didn't create functions but value bindings. test_1 is a value. test_1() is a function of type unit -> unit. Make sure you put () after the function name.
I don't fully understand the scenario you're describing - F# functions declared in a module will generally appear as methods and values will appear as properties. The code that is executed when you first access module (type initialization) is the initialization of values.
If you write just:
module Foo =
let Operation () =
printfn "hello"
...then calling Operation will be a method and calling Foo.Operation() will run the side-effect. If you can post some code that behaves unexpectedly, then someone can explain it.
Anyway, if you want to be sure about the behavior, you can write operations as static members of a class:
type Foo =
static member Operation() =
printfn "hello"
Then you can be sure that F# will compile them as static members of a class in a predictable way.
How do I call a function that needs to be called from above its creation? I read something about forward declarations, but Google isn't being helpful in this case. What is the correct syntax for this?
Lua is a dynamic language and functions are just a kind of value that can be called with the () operator. So you don't really need to forward declare the function so much as make sure that the variable in scope when you call it is the variable you think it is.
This is not an issue at all for global variables containing functions, since the global environment is the default place to look to resolve a variable name. For local functions, however, you need to make sure the local variable is already in scope at the lexical point where you need to call the value it stores, and also make sure that at run time it is really holding a value that can be called.
For example, here is a pair of mutually recursive local functions:
local a,b
a = function() return b() end
b = function() return a() end
Of course, that is also an example of using tail calls to allow infinite recursion that does nothing, but the point here is the declarations. By declaring the variables with local before either has a function stored in it, those names are known to be local variables in lexical scope of the rest of the example. Then the two functions are stored, each referring to the other variable.
You can forward declare a function by declaring its name before declaring the actual function body:
local func1
local func2 = function()
func1()
end
func1 = function()
--do something
end
However forward declarations are only necessary when declaring functions with local scope. That is generally what you want to do, but Lua also supports a syntax more like C, in which case forward declaration is not necessary:
function func2()
func1()
end
function func1()
--do something
end
Testing under the embedded lua in Freeswitch, forward declaration does not work:
fmsg("CRIT", "It worked.")
function fmsg(infotype, msg)
freeswitch.consoleLog(infotype, msg .. "\n")
end
result:
[ERR] mod_lua.cpp:203 /usr/local/freeswitch/scripts/foo.lua:1: attempt to call global 'fmsg' (a nil value)
Reversing the order does (duh) work.
To comprehend how forward referencing in Lua works compared to C, you must understand the a fundamental difference between C compilation and the Lua execution.
In C, forward referencing is a compile time mechanism. Hence if you include a forward declaration template in a C module then any of your code following will employ this template in compiling the call. You may or may not include the function implementation in the same module, in which case both declarations must be semantically identical or the compiler will error. Since this is a compile time construct, the compiled code can be executed in any order.
In Lua, forward referencing is runtime mechanism, in that the compiled function generates a function prototype internally within the code, but this is only accessible as a runtime Lua variable or value after the execution has
passed over the declaration creating a Lua closure. Here the declaration order within the source is immaterial. It is the execution order that is important: if the closure hasn't been bound to the variable yet, then the execution will throw a "nil value" exception.If you are using a local variable to hold the function value, then normal local scoping rules still apply: the local declaration must precede its use in the source and must be within scope, otherwise the compiler will compile in the wrong global or outer local reference. So forward referencing using locals as discussed in other answer will work, but only if the Protos are bound to closures before the first call is executed.
Doesn't work for me if I try to call the function before definition. I am using this Lua script in nginx conf.
lua entry thread aborted: runtime error: lua_redirect.lua:109: attempt to call global 'throwErrorIfAny' (a nil value)
Code snippet -
...
throwErrorIfAny()
...
function throwErrorIfAny()
ngx.say("request not allowed")
ngx.exit(ngx.HTTP_OK)
end
Given some other answers have also pointed out that it didn't work for them either, it is possible that forward declaration of Lua doesn't work with other tools.
PS : It works fine if I put the function definition before and then call it after wards.
If you use OOP you can call any function member prior its "definition".
local myClass = {}
local myClass_mt = { __index = myClass }
local function f1 (self)
print("f1")
self:later() --not yet "delared" local function
end
local function f2 (self)
print("f2")
self:later() --not yet "declared" local function
end
--...
--later in your source declare the "later" function:
local function later (self)
print("later")
end
function myClass.new() -- constructor
local this = {}
this = {
f1 = f1,
f2 = f2,
later = later, --you can access the "later" function through "self"
}
setmetatable(this, myClass_mt)
return this
end
local instance = myClass.new()
instance:f1()
instance:f2()
Program output:
f1
later
f2
later
I can't understand how to define default values for functions in my library. Default values tend to be ignored and I get "wrong parameters count" error message.
Here is my example. I created simple test library experts\libraries\test.mq4:
void test(int i = 0) // Note the default value for "i"
{
}
Then I created .mqh file as experts\include\test.mqh:
#import "test.ex4"
void test(int i = 0); // Note the default value for "i"
#import
Now I create simple expert "experts\simpletest.mq4":
#include <test.mqh>
int start()
{
// Should be able to call test() function without providing any arguments,
// because it has default value.
// If I change this line to test(0), everything compiles correctly
test(); // Causes "wrong parameters count" compilation error
return(0);
}
And I get the following error for test() function call:
')' - wrong parameters count
If I change this function call to test(0), everything compiles, but I should be able to call test() function without providing any parameters, because I have default value for first parameter in .mqh file, like this: void test(int i = 0);
Why it doesn't use the default value?
I search google for any clue, but can't find any references about this problem. Anybody knows?
This is not possible as stated in the MQL Documentation:
MQL4-library functions imported within other modules cannot have parameters initialized by default values.