Parsing one line try catch

General Usage
1

I was surprised that the following line does not parse:

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.11.6 (2025-07-09)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> try 1 catch e1 (-Inf) end
ERROR: ParseError:
# Error @ REPL[1]:1:12
try 1 catch e1 (-Inf) end
#          └────────┘ ── a variable name is expected after `catch`
Stacktrace:
 [1] top-level scope
   @ none:1

julia>

Can anyone explain why this fails and what would be the best working alternative? My best working alternative so far is:

try 1 catch e1 Inf * (-1) end

I would prefer a one line solution.

2

You can just use semicolons:

julia> try 1; catch e1; (-Inf); end
1
2 Likes
3

Use semicolons to separate statements if you don’t want literal line breaks

julia> try 1; catch e1; -Inf; end
1

julia> try error(); catch e1; -Inf; end
-Inf

EDIT: too slow

2 Likes
4

I had a vague memory of most control-flow blocks in Julia requiring new-line or ; to work, but the following works fine (julia v1.11.6):

if true print("true") else print("false") end

for x in 1:3 println("hello") end

Not sure if there is some specific reason that the try-catch block specifically does not behave the same.

1 Like
5

The issue is when there is parsing ambiguity on where one expression ends and another begins:

julia> for x in 1:3 x |> println end
1
2
3

julia> for x in 1:3 +x |> println end # parse as `for x in (1:(3+x) |> println) end`
ERROR: UndefVarError: `x` not defined in `Main`

julia> x = 4;

julia> for x in 1:3 +x |> println end # parse as `for x in (1:(3+x) |> println) end`
1:7
ERROR: MethodError: no method matching iterate(::Nothing)
3 Likes
6

For it to make sense in the OP, not just ambiguous statements but also “too close for comfort” statements are not allowed, because

julia> e1 (-Inf)
ERROR: ParseError:
# Error @ REPL[8]:1:3
e1 (-Inf)
# ╙ ── whitespace is not allowed here
Stacktrace:
 [1] top-level scope
   @ none:1

julia>

is not ambiguous.

Whatever the reason, using semicolon is a good solution, it even allows making the statement shorter:

try 1 catch; -Inf end