# A confusing problem of pipe
**URL:** https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438
**Category:** General Usage
**Tags:** piping
**Created:** [May 19, 2021, 1:07pm UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438 "2021-05-19T13:07:35Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@314](https://discourse.julialang.org/u/314)
#### Post date: [May 19, 2021, 1:07pm UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/1 "2021-05-19T13:07:35Z")
This is my code
```julia
split("hello-world julia", [' ', '-']) .|>
x -> filter(isletter, x) .|>
first .|>
uppercase |>
join
```
I want to get the result `"HWJ"`, but I get a
```julia
3-element Vector{String}:
"H"
"W"
"J"
```
When I use the `Pipe` package, the code works fine. The result is `"HWJ"`
```julia
using Pipe
@pipe split("hello-world julia", [' ', '-']) .|>
filter(isletter, _) .|>
first .|>
uppercase |>
join
```
and following code always has an error no matter how many parentheses are added
```julia
@pipe split(phrase, [' ', '-']) .|>
filter(isletter, _) |>
filter(x -> length(x) > 0, _) .|>
first .|>
uppercase |>
join
```
I’m very confused.
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [May 19, 2021, 1:55pm UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/2 "2021-05-19T13:55:29Z")
```julia
julia> split("hello-world julia", [' ', '-']) .|>
(x -> filter(isletter, x)) .|>
first .|>
uppercase |>
join
"HWJ"
```
anonymous function (`->`) has lower precedence than pipe
---
### Author:  [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [May 19, 2021, 2:40pm UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/3 "2021-05-19T14:40:28Z")
I think the Chain.jl syntax is cleaner
```julia
using Chain: @chain
@chain "hello-world julia" begin
split([' ', '-'])
filter.(isletter, _)
first.()
uppercase.()
join
end
```
---
### Author:  [@314](https://discourse.julialang.org/u/314)
#### Post date: [May 19, 2021, 3:25pm UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/4 "2021-05-19T15:25:33Z")
Thanks for your help!
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [May 19, 2021, 6:59pm UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/5 "2021-05-19T18:59:02Z")
There was recently an [announcement](https://discourse.julialang.org/t/ann-datapipes-jl/60734) of new piping package DataPipes.jl by @aplavin.
Wondering if code below is a proper way of writing requested task:
```julia
using DataPipes
@p begin
"hello-world julia" |>
split(_, [' ', '-'])
filter.(isletter,↑)
first.(↑)
uppercase.(↑)
join
end
```
result seems correct at least: `"HWJ"`
---
### Author:  [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [May 20, 2021, 12:05am UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/6 "2021-05-20T00:05:23Z")
Nice. How do you type the \uparrow?
---
### Author:  [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [May 20, 2021, 12:10am UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/7 "2021-05-20T00:10:48Z")
I am completely confused by this example
No idea what’s going on.
---
### Author:  [@314](https://discourse.julialang.org/u/314)
#### Post date: [May 20, 2021, 1:43am UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/8 "2021-05-20T01:43:19Z")
I think it’s the same with `map(x->(a=x, b=x^2, c=1:x), [1,2,3,4])`, and return a vector of namedtuple
---
### Author:  [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [May 20, 2021, 2:50am UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/9 "2021-05-20T02:50:38Z")
so u can skip the `x->`. Don’t feel this is very intuitive. After skimming thru the documentation, it doesn’t seem to explain that.
---
### Author:  [@aplavin](https://discourse.julialang.org/u/aplavin)
#### Post date: [May 20, 2021, 8:48am UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/10 "2021-05-20T08:48:38Z")
The following snippet would be slightly more along the spirit of `DataPipes.jl`:
```julia
@p begin
split("hello-world julia", [' ', '-'])
filter.(isletter,↑)
map(first)
map(uppercase)
join
end
```
I haven’t really considered broadcasting as pipeline steps yet, so unlike regular function calls they don’t enjoy automatic substitution of the previous step results.
---
### Author:  [@aplavin](https://discourse.julialang.org/u/aplavin)
#### Post date: [May 20, 2021, 8:55am UTC](https://discourse.julialang.org/t/a-confusing-problem-of-pipe/61438/11 "2021-05-20T08:55:20Z")
> [@xiaodai](#):
>
> Nice. How do you type the \uparrow?
Just type `\uparrow`, or `\upar`.
> [@xiaodai](#):
>
> so u can skip the `x->` . Don’t feel this is very intuitive. After skimming thru the documentation, it doesn’t seem to explain that.
This is the whole point of `DataPipes.jl`: to get rid of code overhead when using common data processing functions. Such functions typically take a function as their first argument (or arguments, if multiple), and the dataset as the last argument: think `map/filter/sort/...` in `Base` or `group/join/...` in `SplitApplyCombine`. So, `map(_ + 1)` translates to `map(x -> x + 1, )` and so on.
Agree that the documentation is far from perfect, I just found it easiest for me to put examples showcasing main features instead of extended description.