Prompts & Messages

Prompts in Sema are composable data structures — not string templates. They are built from message expressions and can be inspected, transformed, and composed before being sent to an LLM.

Messages

message

Create a message with a role and content.

(message :system "You are a helpful assistant.")
(message :user "What is Lisp?")
(message :assistant "Lisp is a family of programming languages.")

message/role

Get the role of a message.

(message/role (message :user "hi"))     ; => :user

message/content

Get the content of a message.

(message/content (message :user "hi"))  ; => "hi"

Prompts

prompt

Build a prompt from message expressions. This creates a composable data structure.

(define review-prompt
  (prompt
    (system "You are a code reviewer. Be concise.")
    (user "Review this function.")))

prompt/append

Compose prompts by appending one to another.

(define base (prompt (system "You are helpful.")))
(define question (prompt (user "What is 2+2?")))
(define full (prompt/append base question))

(llm/send full)

prompt/messages

Get the list of messages from a prompt.

(prompt/messages my-prompt)   ; => list of message values

prompt/set-system

Create a new prompt with the system message replaced.

(prompt/set-system my-prompt "new system instructions")

Type Predicates

prompt?

Check if a value is a prompt.

(prompt? review-prompt)   ; => #t

message?

Check if a value is a message.

(message? (message :user "hi"))   ; => #t