if, elseif and guards in Julia

Blocks close with end; && and || double as one-line guards.

cloud_pct = 35

# if/elseif/else close with end; the condition takes no parens.
if cloud_pct < 20
    println("Full survey night")
elseif cloud_pct < 60
    println("Bright targets only")
else
    println("Close the dome")
end

# The ternary picks a value; && and || short-circuit as guards.
mode = cloud_pct < 50 ? "imaging" : "standby"
println("Mode: $mode")
cloud_pct < 40 && println("Guider can lock")

How it works

1. if/elseif/else need no parentheses around conditions.
2. The ternary ? : picks a value for an assignment.
3. cond && println(...) runs the right side only when the left holds.

Keywords and builtins used here

• else
• elseif
• end
• if

The run, in numbers

Lines

15

Characters to type

393

Tokens

63

Three-star pace

70 tpm

At the three-star pace of 70 tokens a minute, this run takes about 54 seconds.

Type this snippet

Step 1 of 3 in Control flow, step 4 of 27 in Language basics.

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