M Query Guide

Functions

M Function Invocation

Invoking Functions

M function invocation uses () with parameter passing.

Introduction to M Function Invocation

Function invocation in the M language involves calling a function by its name followed by parentheses. Parameters, if required, are passed within these parentheses. Understanding how to properly invoke functions is crucial for writing efficient and readable M code.

Basic Syntax of Function Invocation

The basic syntax for invoking a function in M is straightforward:

  • FunctionName(Parameter1, Parameter2, ...): Call the function with the specified parameters.

Let’s look at a simple example:

In this example, the add function takes two parameters, x and y, and returns their sum. The function is invoked with the values 5 and 3, resulting in 8.

Using Functions with No Parameters

Functions can also be invoked without any parameters. In such cases, the parentheses are still required, but they remain empty:

This example demonstrates a greet function with no parameters. It simply returns a greeting string when invoked.

Parameter Passing Techniques

In M, parameters can be passed by value or by reference. This distinction is crucial when dealing with mutable data structures:

  • By Value: A copy of the data is passed to the function, ensuring the original data remains unchanged.
  • By Reference: A reference to the data is passed, allowing the function to modify the original data.

Consider the following example:

Here, the function modifyList takes a list and doubles each element. The original list numbers remains unchanged, demonstrating parameter passing by value.

Common Errors in Function Invocation

When invoking functions, developers may encounter common errors such as:

  • Missing Parentheses: Forgetting to include parentheses, even for parameterless functions, results in syntax errors.
  • Incorrect Parameter Count: Passing too few or too many parameters can lead to runtime errors.
  • Type Mismatch: Providing parameters of the wrong type may cause unexpected behavior.

Always ensure that the function’s signature matches the invocation to avoid these issues.

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