# How to push stuct data into a stack in julia
**URL:** https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894
**Category:** New to Julia
**Created:** [January 21, 2019, 9:04pm UTC](https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894 "2019-01-21T21:04:57Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Mahbubar06](https://discourse.julialang.org/u/Mahbubar06)
#### Post date: [January 21, 2019, 9:04pm UTC](https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894/1 "2019-01-21T21:04:57Z")
Hello,
I have a c++ code where I have created a struct data structure and then I created a function to push struct data into a stack. Now I am wondering can I do the same thing in Julia. The C++ code is given below:
```nohighlight
struct SolutionPool {
int varNameArray[SIZE];
double varValueArray[SIZE];
int ObjectiveValue;
int SolutionNo;
SolutionPool* SolutionPointer;
};
SolutionPool* SolutionHead = NULL;
SolutionPool* SolutionTemp = NULL;
void SolutionPush(int varName[SIZE], double varValue[SIZE], int ObjectValue, int SolNo) {
SolutionTemp = new SolutionPool(); //or on the top of the stack
for (int i = 0; i < SIZE; i++) {
SolutionTemp->varNameArray[i] = varName[i];
}
for (int i = 0; i < SIZE; i++) {
SolutionTemp->varValueArray[i] = varValue[i];
}
SolutionTemp->ObjectiveValue= ObjectValue;
SolutionTemp->SolutionNo = SolNo;
SolutionTemp->SolutionPointer = SolutionHead;
SolutionHead = SolutionTemp;
}
```
For your information I am very new in Julia and I dont know any alternative used in julia for pointer. Thank you in advance. Your help will be appreciated.
---
### Author:  [@lostella](https://discourse.julialang.org/u/lostella)
#### Post date: [January 21, 2019, 9:21pm UTC](https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894/2 "2019-01-21T21:21:16Z")
You can start by checking out the [`push!` and `pop!` functions](https://docs.julialang.org/en/v1/base/collections/#Dequeues-1) that allow you to use collections (for example `Array`s) as stacks.
---
### Author:  [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)
#### Post date: [January 21, 2019, 10:29pm UTC](https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894/3 "2019-01-21T22:29:40Z")
Your C++ code constructs a linked list, not a stack. The difference is that linked lists have O(1) insertion, not just amortized O(1), and are incredibly slow to access sequentially (because the CPU can’t hide the memory latency). There are very few cases where linked lists make sense. In julia, a direct translation is even worse because the garbage collector needs to walk your datastructure as well.
Your best bet would be e.g.
```julia
struct Solution{SIZE}
varNameArray::NTuple{SIZE, Int32}
varValueArray::NTuple{SIZE, Float64}
ObjectiveValue::Int32
SolutionNo::Int32
end
const SIZE = 5 #e.g.
const SolutionPool = Vector{Solution{SIZE}}()
SolutionPush(args...) = push!(SolutionPool, Solution(args...))
```
This will `push_back` your solution. Julia vectors can replace C++ deque (which your C/C++ code should probably use), at least for sizes that are below a significant fraction of your memory (my experience with push\_back and push! into giant vectors is pretty bad, both in C++ and julia, but YMMV).
Consider whether you care about size/memory/speed (switch to `Float32`) or convenience (switch to `Int64`). I simply translated your code, but the Int32/Float64 mix is pretty uncommon in julia.
Constant size containers/arrays in julia want to be immutable tuples. Allocation and resize of arrays are effectively foreign function calls into the julia runtime, and the optimizer can’t look inside of these functions; hence, no inlining / constant propagation / inference of sizes / stack allocation (the optimizer _can_ reason about access into arrays).
Or is SIZE very large? Then you might need a `Vector` instead of an `NTuple` after all.
---
### Author:  [@Mahbubar06](https://discourse.julialang.org/u/Mahbubar06)
#### Post date: [January 21, 2019, 10:58pm UTC](https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894/4 "2019-01-21T22:58:39Z")
Thank you Iostella for your suggestion. I tried the following code:
struct SolutionPool
varNameArray
varValueArray
objectivevalue
SolutionNo
end
a=[0.0 1.0 2.0]
b=[3.0 4.0 5.0]
push!(SolutionPool, a, b, 100.0, 1.0)
But the push! function gives method error. Could you tell me whats wrong with my code?
---
### Author:  [@Mahbubar06](https://discourse.julialang.org/u/Mahbubar06)
#### Post date: [January 21, 2019, 10:58pm UTC](https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894/5 "2019-01-21T22:58:41Z")
Thank you @foobar\_Iv2 for your translation of my code and explanation of the details.
---
### Author:  [@lostella](https://discourse.julialang.org/u/lostella)
#### Post date: [January 22, 2019, 6:44am UTC](https://discourse.julialang.org/t/how-to-push-stuct-data-into-a-stack-in-julia/19894/6 "2019-01-22T06:44:21Z")
The `push!` method is likely defined for Julia’s standard collections, and not on your custom `SolutionPool` type. To make your example code works, you should implement something like:
```julia
function push!(pool::SolutionPool, data::Tuple)
...
end
```
Or otherwise follow @foobar_lv2 suggestion of defining `SolutionPool` as a `Vector`, which is simpler.