Setting up Flow

Get from a bare machine to a program that runs, and prove it.

Check what is already there

Run the packaged tool first. It checks everything below in one pass.

flow-doctor

If flow-doctor is not on the path, do the checks by hand:

flow version || ./flow version     # is Flow installed
cc --version                        # is there a C compiler
python3 --version                   # is there a Python host
echo "FLOW_HOST=${FLOW_HOST:-unset}"

Install Flow

macOS, with Homebrew:

brew tap flooooooooooow/flow
brew install flow
flow version

From source, which also gets the examples and tests:

git clone https://github.com/flooooooooooow/flow.git
cd flow
./flow version

From source the command is ./flow, run from inside the checkout. Set FLOW_HOME to that directory so the tools in this pack can find the standard library and examples:

export FLOW_HOME="$HOME/flow"

Install the build tools

Flow compiles to C and then to a native binary, so a C compiler is required.

macOS:

xcode-select --install

Debian or Ubuntu:

sudo apt install build-essential python3

Set the compiler host

This is the step people miss.

println is outside the Stage-A subset, so almost every beginner program needs the Python host. Recommend setting it permanently:

echo 'export FLOW_HOST=python' >> ~/.zshrc   # or ~/.bashrc
source ~/.zshrc

Prove it works

cat > /tmp/flow_smoke.flow <<'EOF'
function main() -> i32 {
    println("Hello, Flow!")
    return 0
}
EOF

FLOW_HOST=python flow run /tmp/flow_smoke.flow

Expected tail:

Hello, Flow!
✅ Program finished
Exit code: 0

The first build takes roughly twenty seconds. That is the C toolchain doing real work, not a hang.

Optional pieces

Diagnosis table

Report back

Give the user the exact command that worked, its real output, and the host that was used. If you changed a shell profile, say which file and which line.