Add some macros.

* Add a variety of let-based macros to abstract common patterns.

docs/manual.scr

@@ -194,6 +194,36 @@ will be returned as an alist:
 
 @end(section)
 
+@begin(section)
+@title(Macros)
+
+@begin(deflist)
+
+@term(Let macros)
+@begin(def)
+
+These are macros that combine a @c(let) or @c(let*) form with a test
+based on the results of the bindings. This is useful for reducing
+common boilerplate where a let is used to perform some operations, and
+some code should be executed based on the results of those bindings.
+
+@cl:with-package[name="kutils"](
+@cl:doc(macro condlet)
+@cl:doc(macro condlet*)
+@cl:doc(macro iflet)
+@cl:doc(macro iflet*)
+@cl:doc(macro unlesslet)
+@cl:doc(macro unlesslet*)
+@cl:doc(macro whenlet)
+@cl:doc(macro whenlet*)
+)
+
+@end(def)
+
+@end(deflist)
+
+@end(section)
+
 @begin(section)
 @title(Symbol index)
 
@@ -220,6 +250,12 @@ described in "Miscellaneous utilities" under "General".)
 @item(@c(compose) is a function defined in @c(on.lisp), described in
 "On Lisp utilities".)
 
+@item(@c(condlet) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
+@item(@c(condlet*) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
 @item(@c(copy-hash-table) is a function defined in
 @c(kutils-hash-tables.lisp), described in "Hash-table related
 utilities".)
@@ -257,6 +293,12 @@ utilities".)
 @c(kutils-hash-tables.lisp), described in "Hash-table related
 utilities".)
 
+@item(@c(iflet) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
+@item(@c(iflet*) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
 @item(@c(interpose) is a function defined in @c(kutils.lisp),
 described in "Miscellaneous utilities" under "Clojure-inspired
 functions".)
@@ -295,6 +337,18 @@ Lisp utilities".)
 @item(@c(take) is a function defined in @c(kutils.lisp), described in
 "Miscellaneous utilities" under "Clojure-inspired functions".)
 
+@item(@c(unlesslet) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
+@item(@c(unlesslet*) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
+@item(@c(whenlet) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
+@item(@c(whenlet*) is a macro defined in @c(macros.lisp), described in
+"Macros".)
+
 @item(@c(with-new-hash-table) is a macro defined in
 @c(kutils-hash-tables.lisp), described in "Hash-table related
 utilities".)
@@ -318,6 +372,8 @@ Alphabetical documentation for all exported symbols.
 @cl:doc(function build-vector)
 @cl:doc(function cartprod2)
 @cl:doc(function compose)
+@cl:doc(macro condlet)
+@cl:doc(macro condlet*)
 @cl:doc(function copy-hash-table)
 @cl:doc(macro defmacro!)
 @cl:doc(function drop)
@@ -329,6 +385,8 @@ Alphabetical documentation for all exported symbols.
 @cl:doc(function group)
 @cl:doc(function hash-table-to-alist)
 @cl:doc(function hashkeys)
+@cl:doc(macro iflet)
+@cl:doc(macro iflet*)
 @cl:doc(function interpose)
 @cl:doc(function macroexpand-n)
 @cl:doc(macro mapv)
@@ -341,6 +399,10 @@ Alphabetical documentation for all exported symbols.
 @cl:doc(macro sethash)
 @cl:doc(function symb)
 @cl:doc(function take)
+@cl:doc(macro unlesslet)
+@cl:doc(macro unlesslet*)
+@cl:doc(macro whenlet)
+@cl:doc(macro whenlet*)
 @cl:doc(macro with-new-hash-table)
 @cl:doc(function zip))
 

macros.lisp

@@ -0,0 +1,70 @@
+;;;; macros.lisp
+
+(in-package #:kutils)
+
+;;; Various utility macros.
+
+(defmacro when (bindings &body body)
+  "Evaluate the bindings in a let form; if they all evaluate to T,
+evaluate @c(body) in an implicit @c(progn)."
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let (,@bindings)
+       (when (and ,@(mapcar #'first bindings))
+	 ,@body))))
+
+(defmacro whenlet* (bindings &body body)
+  "Evaluate @c(bindings) in a @c(let*) form; if they all evaluate to T,
+evaluate @c(body), which is wrapped in an implicit @c(progn)."
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let* (,@bindings)
+       (when (and ,@(mapcar #'first bindings))
+	 ,@body))))
+
+(defmacro unlesslet (bindings &body body)
+  "Evaluate the bindings in a let form; if they don't all evaluate to T,
+evaluate @c(body) in an implicit @c(progn)."
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let (,@bindings)
+       (unless (and ,@(mapcar #'first bindings))
+	 ,@body))))
+
+(defmacro unlesslet* (bindings &body body)
+  "Evaluate @c(bindings) in a @c(let*) form; if they are all not NIL,
+evaluate @c(body), which is wrapped in an implicit @c(progn)."
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let* (,@bindings)
+       (unless (and ,@(mapcar #'first bindings))
+	 ,@body))))
+
+(defmacro iflet (bindings &body (then &optional else))
+  "Evaluate @c(bindings) in a @c(let) form; if they are all T, execute
+the @c(then) form. Otherwise, execute the @c(else) form."  
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let* (,@bindings)
+       (if (and ,@(mapcar #'first bindings))
+	   (progn ,then)
+	   (progn ,else)))))
+
+(defmacro iflet* (bindings &body (then &optional else))
+  "Evaluate @c(bindings) in a @c(let*) form; if they are all T, execute
+the @c(then) form. Otherwise, execute the @c(else) form."
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let* (,@bindings)
+       (if (and ,@(mapcar #'first bindings))
+	   (progn ,then)
+	   (progn ,else)))))
+
+(defmacro condlet (bindings &body forms)
+  "Evaluate @c(bindings) in a @c(let) form, then evaluate @c(forms) in
+a @c(cond)."
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let (,@bindings)
+       (cond ,@forms))))
+
+(defmacro condlet* (bindings &body forms)
+  "Evaluate @c(bindings) in a @c(let*) form, then evaluate @c(forms) in
+a @c(cond)."
+  (let ((bindings (if (listp (first bindings)) bindings (list bindings))))
+    `(let (,@bindings)
+       (cond ,@forms))))
+

package.lisp

@@ -40,4 +40,14 @@
 	   #:copy-hash-table
            #:hash-table-to-alist
            #:alist-to-hash-table
+
+	   ;; macros.lisp
+	   #:whenlet
+	   #:whenlet*
+	   #:unlesslet
+	   #:unlesslet*
+	   #:iflet
+	   #:iflet*
+	   #:condlet
+	   #:condlet*
            ))