(in-package :losh.control-flow)
(defmacro _ (expr &rest forms)
"Thread the given forms, with `_` as a placeholder."
;; I am going to lose my fucking mind if I have to program lisp without
;; a threading macro, but I don't want to add another dep to this library, so
;; here we are.
`(let* ((_ ,expr)
,@(mapcar (lambda (form)
(if (symbolp form)
`(_ (,form _))
`(_ ,form)))
forms))
_))
(defmacro nest (&rest forms)
"Thread the given forms, putting each as the body of the previous.
Example:
(nest (multiple-value-bind (a b c) (foo))
(when (and a b c))
(multiple-value-bind (d e f) (bar))
(when (and d e f))
(do-something))
macroexpands to:
(multiple-value-bind (a b c) (foo)
(when (and a b c)
(multiple-value-bind (d e f) (bar)
(when (and d e f)
(do-something)))))
"
;; thanks, Fare
(reduce (lambda (prefix body) `(,@prefix ,body))
forms :from-end t))
(defmacro recursively (bindings &body body)
"Execute `body` recursively, like Clojure's `loop`/`recur`.
`bindings` should contain a list of symbols and (optional) starting values.
In `body` the symbol `recur` will be bound to the function for recurring.
This macro doesn't perform an explicit tail-recursion check like Clojure's
`loop`. You know what you're doing, right?
Example:
(defun length (some-list)
(recursively ((list some-list)
(n 0))
(if (null list)
n
(recur (cdr list) (1+ n)))))
"
(flet ((extract-var (binding)
(if (atom binding) binding (first binding)))
(extract-val (binding)
(if (atom binding) nil (second binding))))
`(labels ((recur ,(mapcar #'extract-var bindings)
,@body))
(recur ,@(mapcar #'extract-val bindings)))))
(defmacro when-found ((var lookup-expr) &body body)
"Perform `body` with `var` bound to the result of `lookup-expr`, when valid.
`lookup-expr` should be an expression that returns two values, the first being
the result (which will be bound to `var`) and the second indicating whether
the lookup was successful. The standard `gethash` is an example of a function
that behaves like this.
If the lookup was successful, `body` will be executed and its value returned.
Example:
(multiple-value-bind (val found) (gethash :foo hash)
(when found
body))
; becomes
(when-found (val (gethash :foo hash))
body)
"
(with-gensyms (found)
`(multiple-value-bind (,var ,found) ,lookup-expr
;; We could preserve and pass along the value of found as a secondary
;; return value from the form, but that would kill potential last-call
;; optimization (and the ability to return multiple values from `body`).
(when ,found
,@body))))
(defmacro if-found ((var lookup-expr) then else)
"Perform `then` or `else` depending on the results of `lookup-expr`.
`lookup-expr` should be an expression that returns two values, the first being
the result and the second indicating whether the lookup was successful. The
standard `gethash` is an example of a function that behaves like this.
If the lookup was successful, `then` will be executed with `var` bound to the
result, and its value returned.
Otherwise `else` will be executed and returned, without any extra bindings.
Example:
(multiple-value-bind (val found) (gethash :foo hash)
(if found
'yes
'no))
; becomes
(if-found (val (gethash :foo hash))
'yes
'no)
"
(with-gensyms (found result)
`(multiple-value-bind (,result ,found) ,lookup-expr
(if ,found
(let ((,var ,result))
,then)
,else))))
(defmacro gathering (&body body)
"Run `body` to gather some things and return a fresh list of them.
`body` will be executed with the symbol `gather` bound to a function of one
argument. Once `body` has finished, a list of everything `gather` was called
on will be returned.
It's handy for pulling results out of code that executes procedurally and
doesn't return anything, like `maphash` or Alexandria's `map-permutations`.
The `gather` function can be passed to other functions, but should not be
retained once the `gathering` form has returned (it would be useless to do so
anyway).
Examples:
(gathering
(dotimes (i 5)
(gather i))
=>
(0 1 2 3 4)
(gathering
(mapc #'gather '(1 2 3))
(mapc #'gather '(a b)))
=>
(1 2 3 a b)
"
(with-gensyms (result)
`(let ((,result (make-queue)))
(flet ((gather (item)
(enqueue item ,result)
item))
,@body)
(queue-contents ,result))))
(defmacro gathering-vector ((&key (size 16) (element-type t)) &body body)
"Run `body` to gather some things and return a fresh vector of them.
`body` will be executed with the symbol `gather` bound to a function of one
argument. Once `body` has finished, a vector of everything `gather` was
called on will be returned. This vector will be adjustable and have a fill
pointer.
It's handy for pulling results out of code that executes procedurally and
doesn't return anything, like `maphash` or Alexandria's `map-permutations`.
The `gather` function can be passed to other functions, but should not be
retained once the `gathering` form has returned (it would be useless to do so
anyway).
Examples:
(gathering-vector ()
(dotimes (i 5)
(gather i))
=>
#(0 1 2 3 4)
(gathering-vector ()
(mapc #'gather '(1 2 3))
(mapc #'gather '(a b)))
=>
#(1 2 3 a b)
"
(with-gensyms (result)
`(let ((,result (make-array ,size :adjustable t :fill-pointer 0
:element-type ,element-type)))
(flet ((gather (item)
(vector-push-extend item ,result)
item))
,@body)
,result)))
(defmacro when-let (bindings &body body)
"Bind `bindings` in parallel and execute `body`, short-circuiting on `nil`.
This macro combines `when` and `let`. It takes a list of bindings and binds
them like `let` before executing `body`, but if any binding's value evaluates
to `nil` the process stops there and `nil` is immediately returned.
Examples:
(when-let ((a (progn (print :a) 1))
(b (progn (print :b) 2))
(c (progn (print :c) 3)))
(list a b c))
; =>
:A
:B
:C
(1 2 3)
(when-let ((a (progn (print :a) 1))
(b (progn (print :b) nil))
(c (progn (print :c) 3)))
(list a b c))
; =>
:A
:B
NIL
"
;; (when-let ((a 1)
;; (b 2))
;; (+ a b))
;; =>
;; (BLOCK #:BLOCK632
;; (LET ((A (OR 1 (RETURN-FROM #:BLOCK632)))
;; (B (OR 2 (RETURN-FROM #:BLOCK632))))
;; (+ A B)))
(with-gensyms (block)
`(block ,block
(let (,@(loop :for (symbol value) :in bindings
:collect `(,symbol (or ,value (return-from ,block)))))
,@body))))
(defmacro when-let* (bindings &body body)
"Bind `bindings` sequentially and execute `body`, short-circuiting on `nil`.
This macro combines `when` and `let*`. It takes a list of bindings and binds
them like `let` before executing `body`, but if any binding's value evaluates
to `nil` the process stops there and `nil` is immediately returned.
Examples:
(when-let* ((a (progn (print :a) 1))
(b (progn (print :b) 2))
(c (progn (print :c) 3)))
(list a b c))
; =>
:A
:B
:C
(1 2 3)
(when-let* ((a (progn (print :a) 1))
(b (progn (print :b) nil))
(c (progn (print :c) 3)))
(list a b c))
; =>
:A
:B
NIL
"
;; (when-let* ((a 1)
;; (b 2))
;; (+ a b))
;; =>
;; (BLOCK #:BLOCK647
;; (LET* ((A (OR 1 (RETURN-FROM #:BLOCK647)))
;; (B (OR 2 (RETURN-FROM #:BLOCK647))))
;; (+ A B)))
(with-gensyms (block)
`(block ,block
(let* (,@(loop :for (symbol value) :in bindings
:collect `(,symbol (or ,value (return-from ,block)))))
,@body))))
(defmacro if-let (bindings &body body)
"Bind `bindings` in parallel and execute `then` if all are true, or `else` otherwise.
`body` must be of the form `(...optional-declarations... then else)`.
This macro combines `if` and `let`. It takes a list of bindings and binds
them like `let` before executing the `then` branch of `body`, but if any
binding's value evaluates to `nil` the process stops there and the `else`
branch is immediately executed (with no bindings in effect).
If any `optional-declarations` are included they will only be in effect for
the `then` branch.
Examples:
(if-let ((a (progn (print :a) 1))
(b (progn (print :b) 2))
(c (progn (print :c) 3)))
(list a b c)
'nope)
; =>
:A
:B
:C
(1 2 3)
(if-let ((a (progn (print :a) 1))
(b (progn (print :b) nil))
(c (progn (print :c) 3)))
(list a b c)
'nope)
; =>
:A
:B
NOPE
"
(with-gensyms (outer inner)
(multiple-value-bind (body declarations) (alexandria:parse-body body)
(destructuring-bind (then else) body
`(block ,outer
(block ,inner
(let ,(loop :for (symbol value) :in bindings
:collect `(,symbol (or ,value (return-from ,inner))))
,@declarations
(return-from ,outer ,then)))
,else)))))
(defmacro if-let* (bindings &body body)
"Bind `bindings` sequentially and execute `then` if all are true, or `else` otherwise.
`body` must be of the form `(...optional-declarations... then else)`.
This macro combines `if` and `let*`. It takes a list of bindings and binds
them like `let*` before executing the `then` branch of `body`, but if any
binding's value evaluate to `nil` the process stops there and the `else`
branch is immediately executed (with no bindings in effect).
If any `optional-declarations` are included they will only be in effect for
the `then` branch.
Examples:
(if-let* ((a (progn (print :a) 1))
(b (progn (print :b) 2))
(c (progn (print :c) 3)))
(list a b c)
'nope)
; =>
:A
:B
:C
(1 2 3)
(if-let* ((a (progn (print :a) 1))
(b (progn (print :b) nil))
(c (progn (print :c) 3)))
(list a b c)
'nope)
; =>
:A
:B
NOPE
"
(with-gensyms (outer inner)
(multiple-value-bind (body declarations) (alexandria:parse-body body)
(destructuring-bind (then else) body
`(block ,outer
(block ,inner
(let* ,(loop :for (symbol value) :in bindings
:collect `(,symbol (or ,value (return-from ,inner))))
,@declarations
(return-from ,outer ,then)))
,else)))))
(defmacro multiple-value-bind* (bindings &body body)
"Bind each pair in `bindings` with `multiple-value-bind` sequentially.
Example:
(multiple-value-bind*
(((a b) (values 0 1))
((c) (values (1+ b)))
(list a b c))
; =>
; (0 1 2)
From https://github.com/phoe/m-m-v-b
"
(if (null bindings)
`(progn ,@body)
(destructuring-bind ((vars form) &rest bindings) bindings
`(multiple-value-bind ,vars ,form
(multiple-value-bind* ,bindings ,@body)))))
(defmacro do-repeat (n &body body)
"Perform `body` `n` times."
`(dotimes (,(gensym) ,n)
,@body))
(defmacro do-vector
((var-or-vars vector &key (start nil start?) (end nil end?)) &body body)
"Iterate over `vector`, performing `body` with `var-or-vars` bound.
`var-or-vars` can be one of the following:
* `value-symbol`
* `(value-symbol)`
* `(index-symbol value-symbol)`
Successive elements of `vector` will be bound to `value-symbol` while `body`
is executed. If `index-symbol` is given, the current index will be bound to
it.
Returns `nil`.
"
(setf var-or-vars (alexandria:ensure-list var-or-vars)
start (if start? start 0))
(alexandria:once-only (vector start)
(let ((i nil)
(v nil)
(end% (gensym "END")))
(ecase (length var-or-vars)
(1 (setf i (gensym "I")
v (first var-or-vars)))
(2 (setf i (first var-or-vars)
v (second var-or-vars))))
`(do ((,end% ,(if end? end `(length ,vector)))
(,i ,start (1+ ,i)))
((>= ,i ,end%))
(let ((,v (aref ,vector ,i)))
,@body)))))
(defmacro do-range (ranges &body body)
"Perform `body` on the given `ranges`.
Each range in `ranges` should be of the form `(variable from below)`. During
iteration `body` will be executed with `variable` bound to successive values
in the range [`from`, `below`).
`from` can be larger than `below`, in which case the values will be stepped
down instead of up.
If multiple ranges are given they will be iterated in a nested fashion.
Example:
(do-range ((x 0 6 2)
(y 12 10))
(pr x y))
; =>
; 0 12
; 0 11
; 2 12
; 2 11
; 4 12
; 4 11
"
(assert (not (null ranges)) ()
"Ranges to iterate in DO-RANGE must not be null.")
(recursively ((ranges ranges))
(if (null ranges)
`(progn ,@body)
(destructuring-bind (var from to &optional by) (first ranges)
(with-gensyms (cmp)
(once-only (from to by)
`(do ((,cmp (if ,by
(if (minusp ,by) #'<= #'>=)
(if (< ,from ,to) #'>= #'<=)))
(,by (or ,by (if (< ,from ,to) 1 -1)))
(,var ,from (+ ,var ,by)))
((funcall ,cmp ,var ,to))
,(recur (rest ranges)))))))))
(defmacro do-irange (ranges &body body)
"Perform `body` on the given inclusive `ranges`.
Each range in `ranges` should be of the form `(variable from to &optional by)`.
During iteration `body` will be executed with `variable` bound to successive
values according to `by` in the range [`from`, `to`].
`from` can be larger than `to`, in which case the values will be stepped down
instead of up.
If multiple ranges are given they will be iterated in a nested fashion.
Example:
(do-irange ((x 0 4 2)
(y 11 10))
(pr x y))
; =>
; 0 11
; 0 10
; 2 11
; 2 10
; 4 11
; 4 10
"
(assert (not (null ranges)) ()
"Ranges to iterate in DO-RANGE must not be null.")
(recursively ((ranges ranges))
(if (null ranges)
`(progn ,@body)
(destructuring-bind (var from to &optional by) (first ranges)
(with-gensyms (cmp)
(once-only (from to by)
`(do ((,cmp (if ,by
(if (minusp ,by) #'< #'>)
(if (< ,from ,to) #'> #'<)))
(,by (or ,by (if (< ,from ,to) 1 -1)))
(,var ,from (+ ,var ,by)))
((funcall ,cmp ,var ,to))
,(recur (rest ranges)))))))))
(let ((eof (gensym "EOF")))
(defmacro do-file
((symbol path &rest open-options &key (reader '#'read-line) &allow-other-keys)
&body body)
"Iterate over the contents of `file` using `reader`.
During iteration, `symbol` will be set to successive values read from the
file by `reader`.
`reader` can be any function that conforms to the usual reading interface,
i.e. anything that can handle `(read-foo stream eof-error-p eof-value)`.
Any keyword arguments other than `:reader` will be passed along to `open`.
If `nil` is used for one of the `:if-…` options to `open` and this results
in `open` returning `nil`, no iteration will take place.
An implicit block named `nil` surrounds the iteration, so `return` can be
used to terminate early.
Returns `nil`.
Examples:
(do-file (line \"foo.txt\")
(print line))
(do-file (form \"foo.lisp\" :reader #'read :external-format :EBCDIC-US)
(when (eq form :stop)
(return :stopped-early))
(print form))
(do-file (line \"does-not-exist.txt\" :if-does-not-exist nil)
(this-will-not-be-executed))
"
(let ((open-options (alexandria:remove-from-plist open-options :reader)))
(with-gensyms (stream)
(once-only (path reader)
`(when-let ((,stream (open ,path :direction :input ,@open-options)))
(unwind-protect
(do ((,symbol
(funcall ,reader ,stream nil ',eof)
(funcall ,reader ,stream nil ',eof)))
((eq ,symbol ',eof))
,@body)
(close ,stream))))))))