First commit.

lisp/lib/with.el

@@ -0,0 +1,34 @@
+;;; with.el --- conditional eval wrappers -*- lexical-binding: t; -*-
+;;; Commentary:
+;;; Code:
+
+(defmacro with-feature (feature &rest body)
+  "If FEATURE is available, load it and evaluate BODY."
+  (declare (indent defun))
+  `(when (require ,feature nil :noerror)
+     ,@body))
+
+
+(defmacro with-function (function &rest body)
+  "If FUNCTION is available, evaluate BODY."
+  (declare (indent defun))
+  `(when (functionp ,function)
+     ,@body))
+
+
+(defmacro with-executable (executable &rest body)
+  "If EXECUTABLE is available in path, evaluate BODY."
+  (declare (indent defun))
+  `(when (executable-find (symbol-name ,executable))
+     ,@body))
+
+
+(defmacro with-any-executable (executables &rest body)
+  "If any of EXECUTABLES are available in the path, evaluate BODY."
+  (declare (indent defun))
+  `(when (some (lambda (x) (executable-find (symbol-name x))) ,executables)
+     ,@body))
+
+
+(provide 'lib/with)
+;;; with.el ends here