This document provides a concise guide for C programmers transitioning to Fortran. It highlights key differences, focusing on Fortran's array handling (multidimensional arrays and array slicing), subroutines and functions (pass-by-reference semantics and intent attributes), derived types (similar to structs), and modules (for encapsulation and namespace management). The guide emphasizes Fortran's column-major array ordering, contrasting it with C's row-major order. It also explains Fortran's powerful array operations and intrinsic functions, allowing for optimized numerical computation. Finally, it touches on common Fortran features like implicit variable declarations, formatting with FORMAT statements, and the use of ALLOCATE and DEALLOCATE for dynamic memory management.
This document, titled "Fortran for C Programmers," serves as a comprehensive guide for experienced C programmers transitioning to Fortran. It meticulously outlines the key differences and similarities between the two languages, enabling a smoother learning curve. The guide begins by highlighting Fortran's strengths, particularly in numerical computation and scientific computing, emphasizing its array handling capabilities and optimized performance for complex mathematical operations.
The document then delves into the specifics of Fortran syntax and semantics, comparing and contrasting them with their C counterparts. It covers fundamental concepts like data types, variable declarations, and operators, meticulously explaining how these elements differ between the languages. For instance, it discusses the implicit typing conventions in Fortran, where variable names starting with certain letters default to specific data types, unlike C's explicit declarations. It also explores the concept of kind parameters in Fortran, which allow for precise control over the size and precision of numeric types, offering a level of granularity not readily available in standard C.
The guide further elucidates the distinctions in array handling, a cornerstone of Fortran's prowess in scientific computing. It explains Fortran's multidimensional arrays and their column-major order storage, contrasting this with C's row-major order. The document details how array operations and slicing work in Fortran, emphasizing the language's built-in support for vectorized operations, which often leads to significant performance gains compared to equivalent C code using explicit loops.
Control flow structures, including conditional statements (if, else if, else) and loops (do, while), are also meticulously compared. While the basic structure remains largely similar, the guide highlights syntactic variations and specific features like Fortran's "cycle" and "exit" statements for loop control.
Furthermore, the document addresses the topic of functions and subroutines in Fortran, their parameter passing mechanisms (by reference being the default), and how they relate to C's function calls. It clarifies the distinction between subroutines, which do not return values, and functions, which do. The document also explains how to interface Fortran code with C libraries, enabling programmers to leverage existing C code within Fortran projects.
The guide also touches upon advanced Fortran features such as modules, which facilitate code organization and encapsulation similar to C++ classes, and derived types, allowing users to create custom data structures. It explores the concept of operator overloading in Fortran, enabling customized behavior for operators used with derived types.
Finally, the document underscores the importance of compilers and build systems in Fortran development. It briefly discusses the role of compilers in optimizing Fortran code for high-performance computing and provides guidance on compiling and linking Fortran programs. This comprehensive comparison provides a strong foundation for C programmers to understand and effectively utilize the power of Fortran for scientific and numerical computing tasks.
Summary of Comments ( 3 )
https://news.ycombinator.com/item?id=44017832
Hacker News users discuss Fortran's continued relevance, particularly in scientific computing, highlighting its performance advantages and ease of use for numerical tasks. Some commenters share personal anecdotes of Fortran's simplicity for array manipulation and its historical dominance. Concerns about ecosystem tooling and developer mindshare are also raised, questioning whether Fortran offers advantages over modern C++ for new projects. The discussion also touches on specific language features like derived types and allocatable arrays, comparing their implementation in Fortran to C++. Several users express interest in learning modern Fortran, spurred by the linked resource.
The Hacker News post "Fortran for C Programmers" (linking to Fortran documentation aimed at C programmers) generated a moderate discussion with several interesting comments. Many focused on the persistent relevance and niche strengths of Fortran, particularly in scientific computing.
Several commenters highlighted Fortran's continued dominance in high-performance computing (HPC) and specific scientific domains. They pointed out that despite its age, Fortran's design is well-suited for numerical computation and its compilers are highly optimized for performance on specialized hardware like vector processors. This makes it a difficult language to displace in fields like weather forecasting, climate modeling, and computational fluid dynamics, where raw performance is critical.
One commenter even described Fortran as "the COBOL of scientific computing," alluding to its entrenched position and the significant amount of legacy code that continues to function reliably. While this might seem like a criticism, the context suggested an acknowledgement of Fortran's enduring practicality in its domain.
Another thread of discussion revolved around the relative strengths and weaknesses of Fortran compared to C. Commenters discussed the specific advantages Fortran offers for numerical computation, such as its built-in array operations and support for complex numbers. Some users also appreciated Fortran's more straightforward syntax for certain mathematical operations. Conversely, they acknowledged C's greater flexibility for general-purpose programming and its wider ecosystem of libraries and tools.
A few commenters shared personal anecdotes about using Fortran in their own scientific work or education. These stories provided real-world context to the discussion, illustrating the language's continued use in both academic and industrial settings.
The overall sentiment towards Fortran was surprisingly positive, with many commenters acknowledging its continued importance despite the popularity of newer languages. The discussion painted a picture of Fortran as a specialized tool that remains highly effective for its intended purpose, even if its overall popularity has declined. While the number of comments isn't overwhelming, they provide a good overview of the reasons for Fortran's continued existence in the scientific computing world.