What does the symbol () , =>, _ mean in M expression?

[mpi_gov_vn]

Hi guys,

I was reading an article on how to use List.Generate function. It mentions the symbols like "()", "=>" and "_" that I do not understand the meaning. Here's an example:

List.Generate(() => 10, each _ > 0, each _ - 1)

Could you help me explain this? Or better, is there a documentation to this? Thank you.

Reference: https://docs.microsoft.com/en-us/powerquery-m/list-generate

[AlB · Accepted solution]

Hi @mpi_gov_vn 

You use ( )=> to declare (the start of) a function without input arguments in M. 

Check this out: https://docs.microsoft.com/en-us/powerquery-m/m-spec-functions

As for _  ,each is equivalent to

(_)=>

i.e. declaring (the start of) a function where _ is the input argument to the function

Read this excellent article to know more about each and _

https://www.excelguru.ca/blog/2018/01/09/each-keyword-power-query/

Please mark the question solved when done and consider giving a thumbs up if posts are helpful.

Contact me privately for support with any larger-scale BI needs, tutoring, etc.

Cheers 

[mpi_gov_vn]

Thanks @AlB , that hit the spot!