How/where is the M language read loop?

[Walt1010]

I realise that what Im remarking on is probably a beginners viewpoint, but when I look at a M language query, and compare it to a typical language like Python or C , I struggle to understand the flow of control when it comes to process rows of data, or file records. The "input" section is intuitive but where the "loop" is that circles back and reads the next row, isn't explicit. Am I correct?

[v-kongfanf-msft · Accepted solution]

Hi @Walt1010 ,

In M, the concept of looping through rows is abstracted away. Instead, M uses functions and transformations to process data. For example, when you apply a transformation to a table, M applies that transformation to each row without explicitly showing a loop. This can make it seem like there is no control flow, but in reality, M handles it behind the scenes.

In below example, we start by loading the sample data into a table. Then, we add a new column called "Total Sales" that calculates the total sales for each row by multiplying the "Sales" column by 1.1. Notice that there are no explicit loops; the Table.AddColumn function applies the transformation to each row automatically. This is a simple demonstration of how M processes data in a functional and declarative manner.

Best Regards,
Adamk Kong

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[Greg_Deckler]

@Walt1010 You don't really have classic while and for loops in M. You have recursion and you have things like List.Generate where you can emulate their behavior more or less. It's the same story for DAX, no traditional while or for loops but you can emulate their behavior.