Simplify the initialization expression

Oct 13, 2025 by talynt.org 106 views

Introduction

In the world of programming, especially in languages like Fortran, parameter initialization is a crucial aspect of defining constants within a module. However, when dealing with LFortran, a modern Fortran compiler, certain complicated parameter initializations may not be recognized, leading to compilation errors. This article aims to explore this issue, its possible causes, and potential workarounds.

The Problem

Let's take a look at a simple example that demonstrates the problem:

$ cat test.f90
module test_mod

implicit none

logical, parameter :: param=ichar(transfer(1,'a')) == 0

end module test_mod

When we try to compile this code using LFortran, we encounter a semantic error:

$ lfortran -c test.f90
semantic error: Initialization of `param` must reduce to a compile time constant.
 --> test.f90:5:1
  |
5 | logical, parameter :: param=ichar(transfer(1,'a')) == 0
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

However, the same code compiles successfully with other popular Fortran compilers like gfortran, ifort, and nagfor.

Possible Cause

The issue is likely related to the way LFortran handles the transfer function and the ichar function. The transfer function is used to transfer a value from one type to another, while the ichar function is used to convert a character to its ASCII value. In this case, the expression ichar(transfer(1,'a')) == 0 is not recognized as a compile-time constant by LFortran.

Related Issue

This issue is possibly related to a known bug in LFortran, which is tracked in the following GitHub issue: https://github.com/lfortran/lfortran/issues/1484.

Workarounds

While we wait for the issue to be resolved, here are some possible workarounds:

Simplify the initialization expression: Try to simplify the initialization expression to a compile-time constant. For example, you can use a simple assignment like logical, parameter :: param = .true..
Use a different compiler: If possible, try compiling the code with a different Fortran compiler like gfortran, ifort, or nagfor.
Modify the code: If the initialization expression is essential to your code, you can try modifying it to avoid using the transfer and ichar functions.

Conclusion

In conclusion, complicated parameter initialization is not recognized in LFortran, leading to compilation errors. While the issue is possibly related to a known bug, there are some possible workarounds that can be used in the meantime. We hope that this article has provided valuable insights into this issue and has helped you to find a solution to your problem.

Future Development

We hope that the LFortran developers will address this issue in future releases, making the compiler more compatible with other Fortran compilers. In the meantime, we encourage users to report any similar issues and provide feedback to help improve the compiler.

References

LFortran documentation: https://lfortran.org/
GitHub issue: https://github.com/lfortran/lfortran/issues/1484

Additional Tips

Always check the LFortran documentation and GitHub issues before reporting a new issue.
Provide a minimal, reproducible example when reporting an issue.
Be patient and collaborative when working with the LFortran community to resolve issues.
Complicated Parameter Initialization Not Recognized in LFortran: Q&A ====================================================================

Introduction

In our previous article, we explored the issue of complicated parameter initialization not being recognized in LFortran, a modern Fortran compiler. In this article, we will provide a Q&A section to address some common questions and concerns related to this issue.

Q: What is the cause of this issue?

A: The issue is likely related to the way LFortran handles the transfer function and the ichar function. The transfer function is used to transfer a value from one type to another, while the ichar function is used to convert a character to its ASCII value. In this case, the expression ichar(transfer(1,'a')) == 0 is not recognized as a compile-time constant by LFortran.

Q: Is this issue specific to LFortran?

A: No, this issue is not specific to LFortran. However, LFortran is the only compiler that currently reports a semantic error when encountering this code. Other popular Fortran compilers like gfortran, ifort, and nagfor compile the code successfully.

Q: Can I use a different compiler to compile my code?

A: Yes, you can try compiling your code with a different Fortran compiler like gfortran, ifort, or nagfor. However, keep in mind that LFortran is a modern compiler that is designed to be more compatible with other languages and frameworks. If you are using LFortran for a specific reason, it may be worth exploring alternative solutions or workarounds.

Q: How can I simplify my initialization expression?

A: There are several ways to simplify your initialization expression. Here are a few suggestions:

Use a simple assignment like logical, parameter :: param = .true..
Avoid using the transfer function and the ichar function.
Use a different data type or initialization method.

Q: Is there a known bug or issue related to this problem?

A: Yes, this issue is possibly related to a known bug in LFortran, which is tracked in the following GitHub issue: https://github.com/lfortran/lfortran/issues/1484.

Q: How can I report a similar issue or provide feedback to the LFortran community?

A: You can report a similar issue or provide feedback to the LFortran community by:

Creating a new issue on the LFortran GitHub page.
Joining the LFortran mailing list or forum.
Participating in the LFortran community on social media.

Q: What is the current status of this issue?

A: The current status of this issue is that it is being tracked in the LFortran GitHub issue tracker. The LFortran developers are aware of the issue and are working to resolve it. However, no timeline has been provided for a fix.

Conclusion

In conclusion, the complicated parameter initialization not recognized in LFortran is a known issue that is being tracked in the LFortran GitHub issue tracker. While there are some possible workarounds, it is recommended to use a different compiler or simplify the initialization expression. We hope that this Q&A article has provided valuable insights and information to help you address this issue.

Additional Tips

Always check the LFortran documentation and GitHub issues before reporting a new issue.
Provide a minimal, reproducible example when reporting an issue.
Be patient and collaborative when working with the LFortran community to resolve issues.

References

LFortran documentation: https://lfortran.org/
GitHub issue: https://github.com/lfortran/lfortran/issues/1484