Fortran - Functional Programming Concepts - Generic Filtering | Matthias Noback
Filtering arrays with other value types| Matthias Noback
Articles| Matthias Noback
Articles| Matthias Noback
Filtering arrays with other value types| Matthias Noback
Introducing functional programming in Fortran with filtering integers| Matthias Noback
Higher-order functions and closures| Matthias Noback
We’ve encountered several ways of designing functions in a way that allows them to fail for some reason, without stopping the program, or making it otherwise risky or awkward to use the function. We introduced the error_t type which is very flexible. It can be used to provide some information to the caller, helping them understand what went wrong and how it can be fixed. By allowing errors to be wrapped inside others, we can create chains of errors that describe the problem at various abstr...| Software Development & Design on Matthias Noback
Parsing an array of strings to a polyline should fail if one of the strings could not be parsed to a string. But it should also fail if the resulting array of points is empty. Or at least, if that makes sense in the application’s domain. You could say that a polyline with no points is still a polyline, just like an empty set is still a set. Similarly, in some scenarios it may be okay for a polyline to have just a single point. For now, let’s skip the mathematical discussion and take this ...| Software Development & Design on Matthias Noback
Parsing a string to a point may not be successful, and we were able to communicate that to users of parse_point() by returning a custom type called point_or_error_t. What if we want to parse not just one point but a set of points, forming a polyline, from a list of strings? The result of parsing each string separately is a point or an error. Only if the list of those point_or_error_t values contains no error at all should we consider turning the points into a polyline. If any of the values is...| Software Development & Design on Matthias Noback
We looked at optionally returning a value from a function. In the case of average it was an average value, or no value at all. In some more elaborate functions, the “no result” case needs some more explanation to the caller of the function. We may feel the need to communicate what went wrong, or for what reason. This gives the user the opportunity to pass better input next time, or fix some external issue that the program can’t fix itself (e.g. a file not being readable).| Software Development & Design on Matthias Noback
In the previous post we introduced an optional_real_t type to be the return value of an average function, because depending on the size of the array of numbers passed to it this function may or may not return a real value. What if we could just prevent people from calling the average function when they don’t have any numbers? Maybe we’re lagging too far behind if we have to verify the size of the array inside the average function.| Software Development & Design on Matthias Noback
In the previous post we’ve looked at several ways to communicate to the user of a function that something could go wrong, or that maybe the function couldn’t produce the result that the user was looking for. In the case of an average function, we’d want to communicate to the user that in some cases the function can’t produce a meaningful result, namely if the array of numbers is empty. This isn’t really an error, it’s just that we don’t have a way to answer the question “what...| Software Development & Design on Matthias Noback
Fortran doesn’t have exceptions. You can’t jump out of a function when something unexpected happens, then reflect on what happened outside the function, with the help of a try/catch block. As an alternative, intrinsic (built-in) procedures and constructs like write, read and open allow you to pass an integer variable as one of its arguments, to which it will assign a specific value indicating whether an error occurred. For example, when you try to open a file that doesn’t exist, you wil...| Software Development & Design on Matthias Noback
We’ve implemented filter and map operations. The results of both these operations are new arrays. Yet another common operation on arrays is the so-called reduction operation; we “reduce” multiple values to a single value. The most obvious example is calculating the sum of an array of integers: the input is an array (or list) and the output is a single integer: purefunction sum_all(numbers) result(res) integer, dimension(:), intent(in) :: numbers integer:: res integer:: i res =0do i =1, ...| Software Development & Design on Matthias Noback
In the previous post we looked at this dream scenario: list([1, 3, 5, 7]) % filter(divisible_by(3)) % map(square) As mentioned, we can’t chain function calls like this. But we can put intermediate results in local variables and achieve something similar: integers = list([1, 3, 5, 7]) divisible_by_3 = integers%filter(divisible_by(3)) squared = divisible_by_3%map(square) If the intermediate values are all the same type, we can reuse the variable: integers = list([1, 3, 5, 7]) integers = integ...| Software Development & Design on Matthias Noback
Transforming arrays| Matthias Noback
Discovering best practices in PHP & Fortran code| Matthias Noback
Articles| Matthias Noback
A DTO is an object that holds primitive data (strings, booleans, floats, nulls, arrays of these things). It defines the schema of this data by explicitly declaring the names of the fields and their types. It can only guarantee that all the data is there, simply by relying on the strictness of the programming language: if a constructor has a required parameter of type string, you have to pass a string, or you can’t even instantiate the object. However, a DTO does not provide any guarantee th...| Matthias Noback
Having discussed different aspects of simplicity in programming solutions, let’s start with the first topic that should be scrutinized regarding their simplicity: persisting model objects. As you may know, we have competing solutions which fall into two categories: they will follow either the Active Record (AR) or the Data Mapper pattern (DM) (as described in Martin Fowler’s “Patterns of Enterprise Application Architecture”, abbrev. PoEAA).| Matthias Noback
Articles| Matthias Noback
A common misunderstanding in my workshops (well, whose fault is it then? ;)), is about the distinction between a DTO and a value object. And so I’ve been looking for a way to categorize these objects without mistake. What’s a DTO and how do you recognize it? A DTO is an object that holds primitive data (strings, booleans, floats, nulls, arrays of these things). It defines the schema of this data by explicitly declaring the names of the fields and their types. It can only guarantee that al...| Matthias Noback
“As I’m becoming a more experienced programmer, I tend to prefer simple solutions.” Or something similar. As is the case with many programming-related quotes, this is somewhat of a blanket statement because who doesn’t prefer simple solutions? To make it a powerful statement again, you’d have to explain what a simple solution is, and how you distinguish it from not-so-simple solutions. So the million-dollar question is “What is a simple solution?”, and I’ll answer it now.| Matthias Noback
