5. Control Flow

Lash uses end to close structured blocks. That is different from Bash, where if closes with fi, loops close with done, and case closes with esac.

if / elif / else

if mode == "release"
    echo "release"
elif mode == "debug"
    echo "debug"
else
    echo "default"
end

Conditions can use comparisons, regex matches, logical operators, or numeric truthiness.

while and until

var i = 0

while i < 3
    echo $"{i}"
    i++
end

until i == 0
    i--
end

The compiler warns on constant conditions and unreachable loop bodies when it can prove them.

for over ranges

for i in 1..5
    echo $"{i}"
end

for i in 10..2 step -2
    echo $"{i}"
end

Ranges lower to seq. The compiler warns when a constant step does not move toward the range end.

for over arrays, argv, and globs

let names = ["a", "b", "c"]

for name in names
    echo $"{name}"
end

for arg in argv
    echo $"{arg}"
end

for file in ./dist/*.tar.gz
    echo $"{file}"
end

Glob loops lower directly to Bash word/glob iteration and follow the shell's active glob options.

select

select choice in ["yes", "no"]
    echo $"{choice}"
    break
end

select lowers to Bash select. It can iterate over arrays, argv, ranges, or globs.

switch

enum Mode
    Dev
    Release
end

switch mode
    case Mode::Dev, "debug":
        echo "debug"
    case Mode::Release:
        echo "release"
    case _:
        echo "fallback"
end

switch lowers to Bash case. case _: is the wildcard and cannot be combined with other patterns. Duplicate constant case patterns are diagnosed.

break and continue depths

while outer < 10
    while inner < 10
        continue 2
    end
end

break and continue are only valid inside loops. Optional depths must be positive integer literals.