cadcraft/docs/autolisp.md

AutoLISP

CADCraft runs AutoLISP routines (.lsp files). What is here and what is not yet: gaps.md (E1).

Loading and running

• APPLOAD (Tools > Load Application…, alias AP) opens a file browser filtered to .lsp files, starting in the folder the last one came from (kept in the preferences), and runs the chosen file. Cancelling the browser does nothing. A picked file loads as a typed name does, so a routine it starts that asks for a point waits for it. A desktop without a file browser asks for the name on the command line; the web has no file system, so it says to drop the .lsp file on the window and loads it from its contents. Only .lsp files are loaded; anything else is refused.
• (load "name") loads a file by path, with .lsp added when the name has none. A file APPLOAD loaded is found again by its name, also on the web where there is no file system.
• (defun c:NAME …) defines a command: type NAME at the command line. Built-in commands keep their names.
• At the command line, (expression) evaluates and shows the value, and !variable shows a variable. Typed at a command's prompt (not a free-text one), an expression's value answers it: CIRCLE 0,0 (* 2 r).
• Programmatically (scripts, the control channel, MCP, the CLI): lisp {code, inputs?} and appload {path} | {name, text | data} run to the end and return {value, output, error?}. appload also returns commands, the c: commands the file defined, and a JSON call never opens a file dialog. inputs answer get… calls in order (numbers, strings, [x, y] points); a call with none left gets nil.

At startup

CADCraft loads LISP from its support folder, support in the settings folder (on Windows %APPDATA%\CADCraft\support, on macOS ~/Library/Application Support/CADCraft/support, on Linux ~/.config/cadcraft/support; created at first start):

• acad.lsp once per session, into the first drawing; with ACADLSPASDOC set to 1, into every drawing;
• acaddoc.lsp into every drawing opened or created;
• then S::STARTUP, when they define it.

(autoload "file" '("CMD1" "CMD2")) in a startup file makes CMD1 and CMD2 commands that load file (from the support folder too) the first time they are typed. Startup files run to the end without asking for input. A drawing's own folder is never searched: an acaddoc.lsp that came with a downloaded drawing does not run.

Each drawing has its own variables and functions. A routine is one undo step, whatever commands it runs. A routine that waits for input (getpoint, pause) lets the window work meanwhile; Esc stops it with "Function cancelled", which *error* receives. A long loop runs a slice per frame, so the window stays live and Esc stops it too.

The language

Integers are 32-bit and wrap as AutoLISP's do; any real makes arithmetic real. Variables are dynamically scoped: a function's arguments and its locals (after /) are bound while it runs. Symbols are case-insensitive. Reals print with six significant digits.

Nothing a routine does can crash the program: deep recursion is the error "internal stack limit reached", malformed source is a reader error, and every built-in checks its arguments.

Built-in functions

• Forms: quote ' function setq set if cond while repeat foreach progn and or defun defun-q lambda eval apply mapcar load autoload exit quit
• Numbers: + - * / rem 1+ 1- abs min max sqrt exp log sin cos atan expt fix float gcd logand logior lsh ~ = /= < > <= >= zerop minusp numberp
• Lists: car cdr and the c…r combinations up to four levels, cons list append reverse length nth last member assoc subst acad_strlsort, vl-position vl-remove vl-sort vl-remove-if vl-remove-if-not vl-member-if vl-every vl-some vl-list-length vl-consp
• Predicates: atom listp null not type eq equal boundp vl-symbolp
• Strings: strcat strlen substr strcase itoa atoi atof chr ascii read wcmatch, vl-string-search vl-string-subst vl-string-trim vl-string-left-trim vl-string-right-trim vl-string-translate vl-string->list vl-list->string vl-prin1-to-string vl-princ-to-string vl-symbol-name vl-symbol-value vl-filename-base vl-filename-extension vl-filename-directory
• Geometry: polar distance angle inters trans (trans returns the point: no UCS yet)
• Output and files: princ prin1 print prompt terpri alert open close read-line write-line findfile
• Errors: *error*, vl-catch-all-apply vl-catch-all-error-p vl-catch-all-error-message
• Drawing: command (also command-s, vl-cmdf) with pause, a command left open for the next call, and (command) to cancel; getvar setvar; entget entmake entmod entdel entlast entnext entupd handent; ssget (modes X, L, P, I, W, C, F, WP, CP, a point, or the user selecting; filters with wildcards and -4 operators) ssadd ssdel sslength ssname ssmemb sssetfirst ssgetfirst; tblsearch tblnext (LAYER, LTYPE, STYLE, BLOCK, DIMSTYLE, APPID)
• Input: initget getpoint getcorner getdist getangle getorient getreal getint getstring getkword entsel nentsel
• Units: rtos angtos distof angtof
• No-ops: vl-load-com gc redraw; ver

Entity lists use the DXF group codes of CADCraft's DXF files: what entget returns is what a DXF file holds for the object, plus -1 (its name) and 410 (its layout). Angles (groups 50–58) are in radians, as in AutoCAD, where the file holds degrees; entmake, entmod and ssget filters take radians too.

entmake defines blocks: a BLOCK list (2 name, 70 flags, 10 base point, 4 description) begins a definition, the entities made after it go into the block instead of the drawing, and an ENDBLK list adds the block (redefining one of the same name) and returns its name. Flag 1 with a *U name makes an anonymous block, named when it ends. A BLOCK while a definition is open, an xref (flag 4), an invalid name, a block that inserts itself and a block being edited in place (REFEDIT) return nil. A definition stays open across routines until ENDBLK, but a routine that fails drops the one it began.

Testing against the corpus

The AutoLISP conformance corpus (#648) lives in its own repository. Point CADCRAFT_LISP_CORPUS at it and run cargo test -p cadcraft-engine --test it lisp_corpus::; without the variable the test says it was skipped.