Playground
(Lispex)
KOENRU

First Program

Run a program, change its result from 5 to 10, and fix a missing parenthesis. Then save a local file or set up your editor.

Run a Lispex program and change one number to see why its result changes from 5 to 10. Start in the browser with no installation.

Run it in the Playground

Open the Playground, replace the editor contents with this program, and choose Run.

LISPEX
(define language "Lispex")

(list 'hello language (+ 2 3))

Result

OUTPUT
(hello "Lispex" 5)

define gives the string "Lispex" the name language. The final expression calls list to collect three values. They are the symbol hello, the string stored as language, and the sum of 2 and 3. The quote before hello keeps that name as data.

The Playground shows the values of expressions written at the outermost level of the program. define itself produces no displayed value.

Change 3 to 8 and run again.

Result

OUTPUT
(hello "Lispex" 10)

The last item changes because (+ 2 8) returns 10. The symbol and string stay the same.

Fix a missing parenthesis

Replace the editor contents with this example. Its first line is missing a closing parenthesis.

LISPEX
(define total 10

(+ total 5)

Lispex reports error E100. It cannot finish reading the first expression, so it runs none of the program. Add ) after 10 and run again.

Result

OUTPUT
15

The corrected program defines total as 10, then adds 5. See Diagnostics for errors during reading, syntax expansion, execution, or resource use.

Exercise

Return to the first program and change it to produce this result.

(hello "Lispex" 12)
Show one answer

Change the final expression to (list 'hello language (* 3 4)). Lispex calculates (* 3 4) before list receives its three values.

Continue to Step 2

When you can explain the name, string, nested call, and final list, continue to Values, Names, and Procedures. The remaining sections are for local files and editor setup.

Save and run a local file

Save the original program with (+ 2 3) as hello.lspx. With Node.js installed, run it through the npm package.

SHELL
npx lispex hello.lspx

Or install the Native program for your platform from Downloads and run the same file.

SHELL
lispex hello.lspx

Both commands print this result and exit with status 0.

(hello "Lispex" 5)

Both use the reference implementation written in Rust. npm runs its WASM build, while Native runs it directly. Downloads includes installation and checksum instructions.

For the unfinished example, save the code as unfinished.lspx and use Native to run lispex unfinished.lspx. It exits with status 1 and writes this diagnostic to standard error.

E100 unfinished.lspx:1:1 unterminated list (missing `)`)

To prepare a compiled file later, follow Run Verified Bytecode.

Add syntax highlighting and formatting

The official extension, studiohaze.lispex, highlights .lspx syntax and adds a file icon for light and dark themes.

Formatting requires a separately installed Native CLI. Use Format Document or format-on-save to rewrite the document with consistent spacing and layout. The extension passes the document to lispex fmt - and uses the formatted source it returns. Set lispex.format.executable if the program is not on PATH.

The extension provides syntax highlighting, icons, and formatting. Run code in the Playground or a CLI to see values and diagnostics. For formatting, use Native.