common-lisp-ecosystem

name	Common Lisp Ecosystem
description	This skill should be used when the user asks to "write common lisp", "CLOS", "ASDF", "defpackage", "defsystem", or works with Common Lisp, SBCL, or Coalton. Provides comprehensive Common Lisp ecosystem patterns and best practices.
version	2.0.0

Provide comprehensive patterns for Common Lisp, CLOS, ASDF system definition, SBCL-specific features, and Coalton integration. Read - Analyze ASDF system definitions and Lisp source files Edit - Modify Common Lisp code and system definitions Bash - Run SBCL, Roswell, Qlot commands mcp__plugin_claude-code-home-manager_context7__query-docs - Fetch ASDF, SBCL, and library documentation Homoiconic syntax: code and data share the same structure, enabling powerful macro systems Generic functions with multiple dispatch; method combination (:before, :after, :around) Handler-case for catching, restart-case for recovery points; more powerful than exceptions Namespace management with defpackage; use :import-from or local-nicknames over bare :use

<common_lisp_fundamentals> Code and data share the same syntax (homoiconicity). Enables powerful macro systems for code transformation.

First-class named objects used for identifiers. Interned in packages, can have value, function, and property list. Functions can return multiple values using values, multiple-value-bind, multiple-value-list. Special variables with dynamic scope using defvar/defparameter. Convention: *earmuffs* for special variables. Common Lisp Object System - Generic functions and multiple dispatch Define a class with slots. Slot options: :initarg, :initform, :accessor, :reader, :writer, :type, :documentation. (defclass person () ((name :initarg :name :accessor person-name) (age :initarg :age :accessor person-age)) (:documentation "Represents a person.")) Define generic functions with multiple method implementations. (defgeneric greet (entity) (:documentation "Greet an entity."))

  (defmethod greet ((p person))
    (format t "Hello, ~a!~%" (person-name p)))
</example>
<decision_tree name="when_to_use">
  <question>Do you need polymorphic behavior based on multiple types?</question>
  <if_yes>Use defgeneric and defmethod for multiple dispatch</if_yes>
  <if_no>Use regular functions for single implementation</if_no>
</decision_tree>

Method qualifiers (:before, :after, :around) for aspect-oriented programming. (defmethod greet :before ((p person)) (format t "Preparing to greet...~%"))

  (defmethod greet :around ((p person))
    (format t "[Start]~%")
    (call-next-method)
    (format t "[End]~%"))
</example>

Classes can inherit from multiple parent classes. Uses C3 linearization for method resolution order. (defclass employee (person job-holder) ((employee-id :initarg :id :accessor employee-id))) Common Lisp condition system - Restarts and handlers Handle conditions similar to try-catch (handler-case (/ 1 0) (division-by-zero (c) (format t "Caught: ~a~%" c) 0)) Handle conditions without unwinding stack (handler-bind ((error #'(lambda (c) (format t "Error occurred: ~a~%" c) (invoke-restart 'use-value 0)))) (restart-case (error "Something went wrong") (use-value (v) v))) Define recovery points (defun parse-entry (entry) (restart-case (parse-integer entry) (use-value (v) :report "Use a different value" :interactive (lambda () (list (read))) v) (skip-entry () :report "Skip this entry" nil))) Can the error be recovered interactively or programmatically? Provide restarts for different recovery strategies Use handler-case for simple error handling Define custom condition types for structured error handling. (define-condition invalid-input (error) ((value :initarg :value :reader invalid-input-value)) (:report (lambda (c stream) (format stream "Invalid input: ~a" (invalid-input-value c))))) Define packages with explicit dependencies and exports. (defpackage #:my-project (:use #:cl) (:import-from #:alexandria #:when-let #:if-let) (:export #:main #:process-data)) Define local package nicknames for shorter, clearer references. (defpackage #:my-project (:use #:cl) (:local-nicknames (#:a #:alexandria) (#:s #:serapeum))) Another System Definition Facility - Build system for Common Lisp (ASDF 3.4+) Basic ASDF system definition with metadata and component dependencies. (defsystem "my-project" :description "My project description" :version "0.1.0" :author "Author Name" :license "MIT" :depends-on ("alexandria" "cl-ppcre") :components ((:file "package") (:file "utils" :depends-on ("package")) (:file "main" :depends-on ("utils")))) Organize system components into modules for better structure. (defsystem "my-project" :components ((:module "src" :components ((:file "package") (:file "core" :depends-on ("package")))) (:module "tests" :depends-on ("src") :components ((:file "test-suite"))))) Infer dependencies from defpackage forms for modern, maintainable systems. (defsystem "my-project" :class :package-inferred-system :depends-on ("my-project/main"))

  ;; In my-project/main.lisp:
  (defpackage #:my-project/main
    (:use #:cl)
    (:import-from #:my-project/utils #:helper))
</example>
<decision_tree name="when_to_use">
  <question>Do you want automatic dependency inference from package definitions?</question>
  <if_yes>Use package-inferred-system for modern projects</if_yes>
  <if_no>Use traditional defsystem with explicit component dependencies</if_no>
</decision_tree>

Define test system with automatic test execution using test-op. (defsystem "my-project/test" :depends-on ("my-project" "fiveam") :components ((:file "tests")) :perform (test-op (o s) (uiop:symbol-call :fiveam '#:run! (uiop:find-symbol* '#:my-test-suite :my-project/test)))) Recommended directory layout for Common Lisp projects. my-project/ ├── my-project.asd ├── src/ │ ├── package.lisp │ ├── utils.lisp │ └── main.lisp └── tests/ └── test-suite.lisp Steel Bank Common Lisp - High-performance implementation (current: SBCL 2.6.x, monthly releases) Create standalone executable with SBCL. (defun main () (format t "Hello, World!~%") (sb-ext:exit :code 0))

  (sb-ext:save-lisp-and-die "my-app"
    :toplevel #'main
    :executable t
    :compression t)
</example>

SBCL threading support with make-thread and mutex synchronization. (defvar *result* nil)

  (let ((thread (sb-thread:make-thread
                  (lambda ()
                    (setf _result_ (heavy-computation)))
                  :name "worker")))
    (sb-thread:join-thread thread))

  ;; Mutex
  (defvar _lock_ (sb-thread:make-mutex))
  (sb-thread:with-mutex (_lock_)
    (critical-section))
</example>

Call C functions from SBCL using sb-alien interface. (sb-alien:define-alien-routine "strlen" sb-alien:int (str sb-alien:c-string))

  (strlen "hello") ; => 5
</example>

Use declarations for type information and optimization settings. Options: type, ftype, inline, optimize. (defun fast-add (x y) (declare (type fixnum x y) (optimize (speed 3) (safety 0))) (the fixnum (+ x y))) SBCL-specific extensions for system interaction and performance tuning. ;; Command-line arguments sb-ext:*posix-argv*

  ;; Execute external programs
  (sb-ext:run-program "/bin/ls" '("-l"))

  ;; Trigger garbage collection
  (sb-ext:gc)

  ;; POSIX interface: sb-posix
  ;; Network sockets: sb-bsd-sockets
</example>

Statically typed functional programming on Common Lisp Define algebraic data types in Coalton with type-safe operations. (coalton-toplevel (define-type (Maybe a) None (Some a))

    (declare safe-div (Integer -> Integer -> (Maybe Integer)))
    (define (safe-div x y)
      (if (== y 0)
          None
          (Some (/ x y)))))
</example>

Define type classes for polymorphic behavior in Coalton. (coalton-toplevel (define-class (Printable a) (print-it (a -> String)))

    (define-instance (Printable Integer)
      (define (print-it x)
        (into x))))
</example>

Coalton compiles to efficient Common Lisp code and is interoperable with regular CL. Use coalton-toplevel for type-safe code sections Coalton functions can call CL functions and vice versa Provides Hindley-Milner type inference with type classes

<common_patterns> Resource management with unwind-protect for cleanup. (defmacro with-open-socket ((var host port) &body body) `(let ((,var (make-socket ,host ,port))) (unwind-protect (progn ,@body) (close-socket ,var))))

Loop macro for iteration with collection, filtering, and accumulation. (loop for item in list for i from 0 when (evenp i) collect item into evens finally (return evens)) Common format directives: ~a (aesthetic), ~s (standard), ~d (decimal), ~f (float), ~% (newline), ~{~} (iteration), ~[~] (conditional). (format t "~a is ~d years old~%" name age) Document functions with docstrings explaining purpose and parameters. (defun my-function (arg) "Docstring describing the function. ARG is the argument description." (process arg))

<standard_libraries> Conservative utility library. Provides essential utilities: when-let, if-let, hash-table-alist, ensure-list, mappings, and more. De facto standard for CL projects.

Comprehensive utility library (superset of alexandria). Provides additional utilities: string manipulation, sequences, types, binding macros, and more. Common Foreign Function Interface. Portable FFI for calling C libraries from Common Lisp. Preferred over implementation-specific FFI (e.g., sb-alien). (cffi:defcfun ("strlen" c-strlen) :int (str :string))

  (c-strlen "hello") ; => 5
</example>

<package_sources> Primary package distribution for Common Lisp. Monthly dist updates with tested library versions.

Complementary distribution with more frequent updates. Tracks latest library versions from GitHub.

<modern_tooling> Per-project dependency manager (like bundler/npm). Manages dependencies via qlfile, supports Quicklisp and Ultralisp distributions. <use_case>Install dependencies from qlfile</use_case> <use_case>Run commands with project dependencies</use_case> qlot install qlot exec ros run

Lisp implementation manager and script runner Install Lisp implementations or libraries Start REPL with specified implementation Build standalone executable ros install sbcl ros run ros build myapp.ros

<context7_integration> Available Context7 documentation libraries for Common Lisp ecosystem.

Common Lisp Docs - General Common Lisp documentation /lisp-docs/lisp-docs.github.io 4.7 580 ASDF - Another System Definition Facility documentation /websites/asdf_common-lisp_dev 7.5 190 SBCL - Steel Bank Common Lisp documentation /sbcl/sbcl 8.0 86 CFFI - Common Foreign Function Interface documentation /websites/cffi_common-lisp_dev 7.5 198 FiveAM - Testing framework documentation /websites/fiveam_common-lisp_dev 7.5 164 Coalton - Statically typed functional programming documentation /coalton-lang/coalton 6.6 568 Use resolve-library-id then get-library-docs for latest documentation. ;; Get ASDF documentation mcp__plugin_claude-code-home-manager_context7__query-docs context7CompatibleLibraryID="/websites/asdf_common-lisp_dev" topic="defsystem"

<best_practices> Use *earmuffs* for special variables Use +plus-signs+ for constants Prefer functional style, minimize mutation Provide restarts for recoverable situations Document exported symbols Use appropriate condition types, not just error Use check-type for argument validation Prefer ASDF package-inferred-system for new projects Consider Qlot for per-project dependency management Use Roswell for portable script execution Use Alexandria and Serapeum as standard utility libraries Use CFFI for foreign function calls (portable across implementations) Consider Coalton for type-safe functional subsystems </best_practices>

<anti_patterns> Global mutable state makes code harder to test and reason about. Pass state explicitly or use closures to encapsulate mutable state.

Using :use for packages other than :cl creates namespace pollution. Use :import-from or package-local-nicknames for clearer dependencies. Ignoring conditions loses error context and recovery opportunities. Handle conditions with handler-case or handler-bind, and provide appropriate restarts. Deeply nested code reduces readability and maintainability. Extract helper functions and use early returns to reduce nesting depth. Using eval in application code is slow and defeats compile-time optimization. Use macros for compile-time code generation or first-class functions for runtime dispatch. Custom reader macros make code harder to read for others. Use reader macros sparingly and document them clearly when necessary. Using the loop macro for all iteration, even when simpler constructs suffice. Use mapcar/remove-if/reduce for simple functional transforms. Consider iterate or series for complex iteration that loop handles poorly. Reserve loop for multi-clause iteration with collection and accumulation. Using simple error signaling without restarts, or catching and discarding conditions. Design APIs with restart-case to offer recovery strategies. Use handler-bind to handle conditions without unwinding the stack when possible. Use ASDF for all system definitions; never load files directly Provide restarts for recoverable error conditions Document all exported symbols with docstrings Target SBCL 2.5+ features; use modern ASDF 3.3+ defsystem patterns; never use legacy DEFINE-SYSTEM forms Use *earmuffs* for special variables, +plus-signs+ for constants Prefer :import-from over bare :use for clear dependencies Use check-type for argument validation at function boundaries Consider package-inferred-system for new projects Understand Lisp code requirements 1. Check ASDF system definition Workflow guidance Step completed 2. Review existing macros and patterns Workflow guidance Step completed 3. Identify CLOS class hierarchies Workflow guidance Step completed Write idiomatic Common Lisp code 1. Use appropriate abstraction level Workflow guidance Step completed 2. Follow condition system for errors Workflow guidance Step completed 3. Design reusable macros carefully Workflow guidance Step completed Verify Lisp code correctness 1. Load system with ASDF Workflow guidance Step completed 2. Run tests with appropriate framework Workflow guidance Step completed 3. Check for compilation warnings Workflow guidance Step completed

<error_escalation inherits="core-patterns#error_escalation"> Style inconsistency Compilation warning or type error Macro expansion error Reader macro conflict </error_escalation>

Apply this skill when task keywords and domain match Use the canonical workflow and verify with project conventions

<decision_tree name="skill_activation"> Does the task clearly match this skill domain? Use this skill workflow and constraints Use a more appropriate domain skill </decision_tree>

<related_agents> Locate code patterns and references in this skill domain Review implementation quality against this skill guidance Analyze code complexity and suggest refactoring improvements </related_agents>

Use ASDF for system definition Follow condition system for error handling Document macros with clear examples Overly complex macros without documentation Global state without clear lifecycle Reader macros without namespace isolation

<related_skills> Navigate CLOS hierarchies, generic functions, and symbol definitions Access ASDF, SBCL, and Common Lisp library documentation Debug condition handling, macro expansion, and SBCL-specific issues Operational SBCL execution, debugger, profiling, and executable build workflows </related_skills>