Matthias Noback

Fortran - Errors and error handling - Part 7 - Fatal errors Stop with error code, error message, and stack trace

New #Fortran post: "Errors and error handling - Part 7 - Fatal errors" matthiasnoback.nl/2025/07/fort...

Almost everywhere in our code should we allow errors to bubble up to higher abstraction levels, until we get to the point that we'd like to terminate the program. How to do that properly?

Fortran - Errors and error handling - Part 6 - Guarantees The Evidence Pattern

New #Fortran post: "Errors and error handling part 6: Guarantees" matthiasnoback.nl/2025/07/fort...

If we want guarantees that data in a DT is correct, we have to use a custom constructor. Such a constructor then needs another Either return type so it can return a validated instance or an error.

Fortran - Errors and error handling - Part 5 - Error propagation Error propagation and nesting

New #Fortran post: Errors and error handling part 5: Error propagation matthiasnoback.nl/2025/07/fort...

We redesign the error value so lower-level errors can be "wrapped" inside higher-level errors.

Fortran - Errors and error handling - Part 4 - Using an Either type Dealing with parse errors

New #Fortran post: "Errors and error handling - Part 4 - Using an Either type" matthiasnoback.nl/2025/07/fort...

We consider a problem that involves parsing and find a solution to deal with errors: a parse function that returns an "Either" type, containing an error, or the expected result.

Fortran - Errors and error handling - Part 3 - Preventing edge cases with types An alternative: the non-empty list type

New #Fortran post: Preventing edge cases with types matthiasnoback.nl/2025/07/fort...

We look at an alternative solution for calculating the average of an empty list; only offer such a procedure for a non-empty list.

Fortran - Errors and error handling - Part 2 Optional results

New #Fortran post: "Errors & Error Handling Part 2 - Optional Results matthiasnoback.nl/2025/07/fort...

Instead of returning a success flag and use an intent(out) argument to return the actual function result, we implement an optional return value using an abstract derived type and two subtypes.

Fortran - Errors and error handling - Part 1 - Exploration Exploring our options

New #Fortran post "Errors and error handling, part 1: Exploration": matthiasnoback.nl/2025/07/fort...

The first part in a series about dealing with errors: we explore some common approaches and what their downsides are.

Fortran - Functional Programming Concepts - Reduce Reducing arrays to a single value

One extra #Fortran post for today: "Functional Programming Concepts - Reduce" matthiasnoback.nl/2025/06/fort...

Having discussed filter and map which transform arrays into new arrays, we still need another function: reduce, which transforms arrays into single values.

Fortran - Functional Programming - List type Adding filter and map behavior to a list type

New #Fortran post: "Functional Programming - List Type" matthiasnoback.nl/2025/06/fort...

By introducing a list type we can bind the functional-style filter and map functions to a derived type, making it possible to "chain" multiple calls.

Fortran - Functional Programming Concepts - Map Transforming arrays

New #Fortran post: "Fortran - Functional Programming Concepts - Map" matthiasnoback.nl/2025/06/fort...

After discussing filter functions, now it's time to work no a map function.

Fortran - Functional programming - Closures Generic filtering

New #Fortran post: "Fortran - Functional Programming Concepts - Closures" matthiasnoback.nl/2025/06/fort...

Fortran doesn't have good support for higher-order functions and closures, can we replicate them?

Fortran - Functional Programming Concepts - Generic Filtering Filtering arrays with other value types

New #Fortran post: "Functional Programming Concepts - Generic filtering" matthiasnoback.nl/2025/06/fort...

Fortran doesn't support generics, which would allow us to reuse the same filter function for arrays of different types of values. In this post we'll explore a work-around for this problem.

Fortran - Functional Programming Concepts: Filter Introducing functional programming in Fortran with filtering integers

New #Fortran post: "Fortran - Functional Programming Concepts: Filter" matthiasnoback.nl/2025/06/fort...

Having looked at Object-Oriented programming concepts in Fortran, we now dive into Functional programming concepts. We start with filtering arrays of integers.

Fortran: Enumeration, part 3 Adding more behavior and introducing enum subtypes

New #Fortran post: "Enumeration, part 3" matthiasnoback.nl/2025/06/fort...

It's surprising how much there is to explore about enumeration types, but here we are with the final part: we further improve the design by making log level an abstract type, and all the concrete levels subtypes.

Fortran: Enumeration, part 2 Type safety, a log level factory, and operator overloading

New #Fortran post: "Enumeration, part 2" matthiasnoback.nl/2025/06/fort...

We increase type safety by narrowing the integer level argument to a derived type argument. A new factory type helps us separate responsibilities. Finally we compare levels using operator overloading.

Fortran: Enumeration, part 1 In the post about decoration we declared log levels as follows: module logging_base ! ... integer, parameter, public :: LOG_DEBUG = 0 integer, parameter, public :: LOG_INFO = 1 integer, parameter,…

New #Fortran post: "Fortran: Enumeration, part 1" matthiasnoback.nl/2025/06/fort...

We are refactoring the integer parameters for the various log levels that we want to support. We want to accomplish type-safety and ease-of-use (pun intended).

Fortran: Module Design Fortran projects are famous for their large modules. Actually, we may also find very large files in legacy projects written in other languages, like Java, PHP, etc. These projects sometimes have…

New #Fortran post: "Module Design" matthiasnoback.nl/2025/06/fort...

We splitt an existing module into smaller modules and put a façade module in front of the smaller ones, so users only have to deal with a simple programming interface. Finally we fix compilation cascade with a submodule.

Fortran: Service Composition, part 2: Decoration In the previous post we saw how to use an abstraction to compose an aggregation of services of that same abstraction. There we simply delegated a call, adding no specific behavior. But we might as…

New #Fortran post: Service Composition, part 2: Decoration matthiasnoback.nl/2025/06/fort...

In this post we explore another way of composing abstractions, which is called decoration. We prefix existing log messages with a timestamp and implement optional delegation based on a configured log level.

Fortran: Service Composition, part 1: Aggregation With our new service abstraction logger_t we are able to easily implement more features for our logger. We can do this without affecting current user code, because their code relies only on the…

New #Fortran post "Fortran: Service Composition, part 1: Aggregation" matthiasnoback.nl/2025/06/fort...

We are ready to build more features into the logging library, using different styles of composition. First we look at aggregation.

Fortran: Abstract Types and Deferred Procedures With the new file_logger_t type we were able to model a logger service as a derived type. Now it’s time to make the service abstract. That is, to leave out the implementation detail that it’s a file…

New #Fortran post: "Abstract Types and Deferred Procedures" matthiasnoback.nl/2025/06/fort...

We define an abstract type with deferred procedures (in OO language: an interface) for the file logger. Introducing an abstract factory allows clients to decouple and shows us how polymorphism works.

Fortran: Modeling Services as Derived Types We’ve seen how to define a derived type to represent a point in 2D space. We were able to add a type-bound procedure to it, and finally to make its components private and define a custom constructor…

New #Fortran post: "Modeling Services as Derived Types" matthiasnoback.nl/2025/06/fort...

Derived types (DTs) can also be used for "service objects". We look at a safe refactoring from module state and subroutines to a DT with a data component and a type-bound procedure.

Fortran: Private Data Components and Custom constructors In the previous post we have worked on the point_t derived type, turning the module procedure distance into a type-bound procedure: module geometry ! ... type :: point_t real :: x real :: y contains…

New #Fortran article: "Private Data Components and Custom Constructors" matthiasnoback.nl/2025/06/fort...

We make the data inside the derived type private (encapsulation), offer alternative ways for creating new instances (factory functions), and expose these alternatives as an abstract function.

Fortran: Type-bound Procedures In the previous post we defined a derived type point_t with real data components x and y, to represent a point in 2D space. We also wrote a function to calculate the distance between two such points:…

New #Fortran post: "Type-bound Procedures" matthiasnoback.nl/2025/06/fort... These are the equivalent of class methods, but can surprisingly still be used as regular functions.

New #Fortran post: "Derived Types" matthiasnoback.nl/2025/06/fort... These are similar to structs or classes in other languages.

New #Fortran post: "Functions and Subroutines" matthiasnoback.nl/2025/05/fort...

New #Fortran post: "Types and variables" matthiasnoback.nl/2025/05/fort...

Next #Fortran post: "Programs and modules" matthiasnoback.nl/2025/05/fort... It looks like this is starting to be a Fortran course for people with experience writing in other programming languages...

Second #Fortran post: "Running a simple Fortran program" matthiasnoback.nl/2025/05/runn... Using very modern tooling :)

Thanks!

It's been a while, but I'm back to blogging: "Hello, Fortran world!" matthiasnoback.nl/2025/05/hell...