Write a reusable custom function

Goal: Package a multi-step transformation — like converting snake_case to CamelCase — into a named function you can call like a builtin.

Prerequisites: None.

Query

def snake_to_camel(x):
  let words = split(x, "_")
  | foreach (word, words):
      let first_char = upcase(first(word))
      | let rest_str = downcase(slice(word, 1, len(word)))
      | s"${first_char}${rest_str}";
  | join("")
end
| snake_to_camel("hello_world")

$ mq -I null 'def snake_to_camel(x): ... end | snake_to_camel("hello_world")'

Output

HelloWorld

Notes

• def ... end must appear before its first use in the pipeline.
• Reuse the same function across many invocations: put it in a .mq module file and load it with -M path/to/module (path without the .mq extension, function used unqualified), or put the file on a search path with -L dir and import "module" (used as module::fn(...)).