how to assign a variable dynamically? | Forex Factory

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how to assign a variable dynamically?

  • #1
  • First Post: Dec 16, 2018 6:35am Dec 16, 2018 6:35am
Inserted Code
int abc1 = 123;
int abc = 456;
int e = 1;
printf (abc+e);

supposedly it will output "123", but it fail with error "abc" is not declare. How to fix the error?
  • #2
  • Dec 16, 2018 6:54am Dec 16, 2018 6:54am
int b = {};
int test = b['abc' + e];
printf (test);

it come with error "single quoted is needed"
  • #3
  • Dec 16, 2018 7:01am Dec 16, 2018 7:01am
Quoting zac1987
int b = {}; int test = b['abc' + e]; printf (test); it come with error "single quoted is needed"
What are you trying to do and in what programming language?
  • #4
  • Dec 16, 2018 7:13am Dec 16, 2018 7:13am
Print and printf are different function.

Inserted Code
int abc1 = 123;
int abc = 456;
int e = 1;
//--
printf (%d,abc+e);
Print(abc+e);
  • #5
  • Dec 16, 2018 7:31am Dec 16, 2018 7:31am
@Hairi
Inserted Code
Print(abc+e);
output 4561
How to code to output 123 ?
  • #6
  • Dec 16, 2018 7:34am Dec 16, 2018 7:34am
Quoting stivborg
{quote} What are you trying to do and in what programming language?
I want to combine variable name, but not combine variable value. In mql4 language.

Inserted Code
int abc = 456;
int e = 1;
How combine value of e into variable name of abc to become abc1?
  • #7
  • Dec 16, 2018 8:35am Dec 16, 2018 8:35am
Quoting zac1987
{quote} I want to combine variable name, but not combine variable value. In mql4 language. int abc = 456; int e = 1; How combine value of e into variable name of abc to become abc1?
I don't code in mql4 yet, but I understand what you are asking.

I did a quick search and it doesn't seem easy to do this directly in mql4. But you may be able to do a workaround by using an array. This workaround is typically used in other languages.
  • #8
  • Dec 16, 2018 8:35am Dec 16, 2018 8:35am
Quoting zac1987
{quote} I want to combine variable name, but not combine variable value. In mql4 language. int abc = 456; int e = 1; How combine value of e into variable name of abc to become abc1?
try

Inserted Code
Print(StringConcatenate("abc","1");
  • #9
  • Dec 16, 2018 8:46am Dec 16, 2018 8:46am
Quoting zac1987
{quote} I want to combine variable name, but not combine variable value. In mql4 language. int abc = 456; int e = 1; How combine value of e into variable name of abc to become abc1?
Most programming languages cannot access a variable by its name declared in the source code. This feature is usual for interpreted languages, however it is rare for the compiled ones.
  • #10
  • Dec 16, 2018 10:13am Dec 16, 2018 10:13am
Quoting Hairi
{quote} try Print(StringConcatenate("abc","1");
I need "e" instead of "1".
Inserted Code
Print(StringConcatenate("abc","e");
and it come with error "";" - unexpected token
  • #11
  • Dec 16, 2018 10:27am Dec 16, 2018 10:27am
Quoting userque
{quote} I don't code in mql4 yet, but I understand what you are asking. I did a quick search and it doesn't seem easy to do this directly in mql4. But you may be able to do a workaround by using an array. This workaround is typically used in other languages.
May I know how to do it in array?
  • #12
  • Dec 16, 2018 10:44am Dec 16, 2018 10:44am
Quoting zac1987
{quote} May I know how to do it in array?
Man, you could not make these things in mql4. And most probably you do not need; figure out something simple. If that much needed, define a string constant and go further.
  • #13
  • Dec 16, 2018 11:07am Dec 16, 2018 11:07am
Quoting zac1987
{quote} May I know how to do it in array?
You can make arrays in MQL4:

https://book.mql4.com/variables/arrays

Here is a brief explanation in another language (same concept regardless of language).

https://stackoverflow.com/questions/...-variable-name
  • #14
  • Last Post: Edited 12:48pm Dec 16, 2018 12:26pm | Edited 12:48pm
EDIT: I think there is a lot of confusion ITT due to the nature of the question. If I am correct OP wants to create dynamic "mappings", and if that's the case he will need to use a hashmap (dicitonary). OP, what is it that you are trying to do because there is almost certainly a better way to do whatever it is that you are trying to do than by creating dynamic mappings.



If you want to output the variable names and results you have to use some MACRO magic.

Inserted Code
#define print(CODE) Print(#CODE, " = ", CODE)

Example time.

Inserted Code
void OnStart()
{
   int a = 1;
   int b = 1;
   int c = 2;
   print((a + b) / c);
   print(TimeCurrent());
   print(my_add(a, b));
}
int my_add(int a, int b)
{
   return a + b;
}

output

Inserted Code
(a+b)/c = 1
TimeCurrent() = 2018.12.14 23:59:58
my_add(a,b) = 2
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