Command Line Flags in Lisp
Here’s the translation of the Go code to Lisp, with explanations in Markdown format suitable for Hugo:
Command-line flags are a common way to specify options for command-line programs. For example, in wc -l
the -l
is a command-line flag.
In this example, we’ll use a hypothetical flag
package to implement basic command-line flag parsing. This package would provide similar functionality to Go’s flag
package.
We start by defining our main
function. Inside this function, we declare our flags:
- We declare a string flag
word
with a default value “foo” and a short description. - We declare an integer flag
numb
with a default value 42. - We declare a boolean flag
fork
with a default value ofnil
(false in Lisp). - We also demonstrate how to declare an option that uses an existing variable
svar
.
After declaring the flags, we call flag:parse
to execute the command-line parsing.
Finally, we print out the parsed options and any trailing positional arguments. Note that we need to dereference the pointers with deref
to get the actual option values.
To experiment with this program, you would compile it and run the resulting binary. Here are some example usages:
Note that if you omit flags, they automatically take their default values. Trailing positional arguments can be provided after any flags.
In Lisp, you would typically use libraries like command-line-arguments
or write custom parsing logic for more complex command-line interfaces. This example provides a simplified illustration of how you might implement similar functionality to Go’s flag package in Lisp.