LD-PROMPT.html -- ACL2 Version 6.3

## LD-PROMPT

determines the prompt printed by `ld`

    Major Section:  MISCELLANEOUS

`Ld-prompt` is an `ld` special (see ld). The accessor is `(ld-prompt state)` and the updater is `(set-ld-prompt val state)`. `Ld-prompt` must be either `nil`, `t`, or a function symbol that, when given an open output character channel and state, prints the desired prompt to the channel and returns two values: the number of characters printed and the state. The initial value of `ld-prompt` is `t`.

The general-purpose ACL2 read-eval-print loop, `ld`, reads forms from `standard-oi`, evaluates them and prints the result to `standard-co`. However, there are various flags that control `ld`'s behavior and `ld-prompt` is one of them. `Ld-prompt` determines whether `ld` prints a prompt before reading the next form from `standard-oi`. If `ld-prompt` is `nil`, `ld` prints no prompt. If `ld-prompt` is `t`, the default prompt printer is used, which displays information that includes the current package, default defun-mode, guard checking status (on or off), and `ld-skip-proofsp`; see default-print-prompt.

If `ld-prompt` is neither `nil` nor `t`, then it should be a function name, `fn`, such that `(fn channel state)` will print the desired prompt to `channel` in `state` and return `(mv col state)`, where `col` is the number of characters output (on the last line output). You may define your own prompt printing function.

If you supply an inappropriate prompt function, i.e., one that causes an error or does not return the correct number and type of results, the following odd prompt will be printed instead:

    Bad Prompt
    See :DOC ld-prompt>

which will lead you to this message. You should either call `ld` appropriately next time or assign an appropriate value to `ld-prompt`.