# Conditional test \`? :\` behave differently if switch the turn of return value
**URL:** https://discourse.julialang.org/t/conditional-test-behave-differently-if-switch-the-turn-of-return-value/51578
**Category:** General Usage
**Tags:** question, function
**Created:** [December 10, 2020, 2:27am UTC](https://discourse.julialang.org/t/conditional-test-behave-differently-if-switch-the-turn-of-return-value/51578 "2020-12-10T02:27:32Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@KyleJT](https://discourse.julialang.org/u/KyleJT)
#### Post date: [December 10, 2020, 2:27am UTC](https://discourse.julialang.org/t/conditional-test-behave-differently-if-switch-the-turn-of-return-value/51578/1 "2020-12-10T02:27:32Z")
Currently, I worked on this homework, _i.e._ [Triangle](https://exercism.io/my/solutions/87674efbb283421e85110c8615aebd40). Some code snippet for test the isosceles is as following:
```julia
reset_pos(idx) = idx == 0 ? 1 : idx
function is_triangle(sides)
i = 1
while i <= length(sides)
sides[i] + sides[reset_pos(mod(i+1,3))] > sides[reset_pos(mod(i+2,3))] ? i = i+1 : return false
end
return true
end
function is_isosceles(sides)
if !is_triangle(sides) return false end
i = 1
while i <= length(sides)
(sides[i] == sides[reset_pos(mod(i+1,4))]) ? return true : i=i+1 # strange thing happens here.
end
return false
end
# test
is_isosceles([1,2,2])
```
if the above code annotated is
```julia
(sides[i] == sides[reset_pos(mod(i+1,4))]) ? return true : i=i+1
```
The compiler warns `ERROR: LoadError: syntax: colon expected in "?" expression`. **However** , if the above code annotated is changed into
```julia
!(sides[i] == sides[reset_pos(mod(i+1,4))]) ? i=i+1 : return true
```
` is_isosceles(sides)` works normally.
I wonder if I missed something. What caused the annotated code snippet behaves wrong?
Thank you.
---
### Author:  [@kevbonham](https://discourse.julialang.org/u/kevbonham)
#### Post date: [December 10, 2020, 2:41am UTC](https://discourse.julialang.org/t/conditional-test-behave-differently-if-switch-the-turn-of-return-value/51578/2 "2020-12-10T02:41:49Z")
Just a guess, but try wrapping the `return` statement in parentheses - that is `... ? (return true) : ...`. I’ve found that most syntax errors I make can be solved with judicious use of parentheses.
I don’t understand it in detail, but it’s something to due with how the parser breaks down your code into expressions. Things like `return` and `=` for assignment are special - I’m guessing that `stuff ? retun foo : bar` gets parsed as `(stuff) ? (return foo : bar)` rather than what you intended `(stuff) ? (return foo) : (bar)`
---
### Author:  [@KyleJT](https://discourse.julialang.org/u/KyleJT)
#### Post date: [December 10, 2020, 2:48am UTC](https://discourse.julialang.org/t/conditional-test-behave-differently-if-switch-the-turn-of-return-value/51578/3 "2020-12-10T02:48:31Z")
Your solution works. Some revisions like the following works. Anyway, let’s wait to see if anyone can offer more details. Thank you.
```julia
(sides[i] == sides[reset_pos(mod(i+1,4))]) ? (return true) : i=i+1
```
---
### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [December 10, 2020, 3:06am UTC](https://discourse.julialang.org/t/conditional-test-behave-differently-if-switch-the-turn-of-return-value/51578/4 "2020-12-10T03:06:00Z")
> [@KyleJT](#):
>
> ```julia
> return true : i=i+1
>
> ```
This is parsed as `return (true : i=i+1)`
Just don’t return in `?:`, use a proper `if`.
---
### Author:  [@KyleJT](https://discourse.julialang.org/u/KyleJT)
#### Post date: [December 10, 2020, 12:43pm UTC](https://discourse.julialang.org/t/conditional-test-behave-differently-if-switch-the-turn-of-return-value/51578/5 "2020-12-10T12:43:58Z")
thank you very much. 囧rz