Beyond Theory: Building Practical Tools with Guile Scheme
+
+
+ •
+ 5 min read
+ •
+ By Glenn Thompson
+
+
+
+
+
Beyond Theory: Building Practical Tools with Guile Scheme
+
Introduction
+
A few months ago, I shared my journey into learning Scheme through building stash, a symlink manager. Since then, I've discovered that the gap between learning Scheme and applying it to real-world problems is where the most valuable lessons emerge. This post explores what I've learned about building practical tools with Guile Scheme, sharing both successes and challenges along the way.
+
The Power of Modular Design
+
One of the most important lessons I learned was the value of modular design. Breaking down a program into focused, single-responsibility modules not only makes the code more maintainable but also helps in reasoning about the program's behavior. Here's how I structured stash:
Modular Design: Breaking the code into focused modules made it easier to maintain and test
+
Functional Approach: Using pure functions where possible made the code more predictable
+
Interactive Interface: Providing clear user prompts and colored output improved usability
+
Robust Logging: Detailed logging helped with debugging and understanding program flow
+
+
Challenges Faced
+
+
Path Handling: Dealing with different path formats and edge cases required careful attention
+
Error States: Managing various error conditions while keeping the code clean
+
User Interface: Balancing between automation and user control
+
Documentation: Writing clear documentation that helps users understand the tool
+
+
Moving Forward
+
Building stash has taught me that while functional programming principles are valuable, pragmatism is equally important. The key is finding the right balance between elegant functional code and practical solutions.
The code examples in this post are from my actual implementation of stash. Feel free to explore, use, and improve upon them!
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+---
+title: Beyond Theory: Building Practical Tools with Guile Scheme
+author: Glenn Thompson
+date: 2024-12-03 10:00
+tags: tech, guile, scheme, development, functional-programming
+---
+
+# Beyond Theory: Building Practical Tools with Guile Scheme
+
+## Introduction
+
+A few months ago, I shared my journey into learning Scheme through building `stash`, a symlink manager. Since then, I've discovered that the gap between learning Scheme and applying it to real-world problems is where the most valuable lessons emerge. This post explores what I've learned about building practical tools with Guile Scheme, sharing both successes and challenges along the way.
+
+## The Power of Modular Design
+
+One of the most important lessons I learned was the value of modular design. Breaking down a program into focused, single-responsibility modules not only makes the code more maintainable but also helps in reasoning about the program's behavior. Here's how I structured `stash`:
+
+```scheme
+(use-modules (ice-9 getopt-long)
+ (stash help) ;; Help module
+ (stash colors) ;; ANSI colors
+ (stash log) ;; Logging module
+ (stash paths) ;; Path handling module
+ (stash conflict) ;; Conflict resolution module
+ (stash file-ops)) ;; File and symlink operations module
+```
+
+Each module has a specific responsibility:
+- `colors.scm`: Handles ANSI color formatting for terminal output
+- `conflict.scm`: Manages conflict resolution when files already exist
+- `file-ops.scm`: Handles file system operations
+- `help.scm`: Provides usage information
+- `log.scm`: Manages logging operations
+- `paths.scm`: Handles path manipulation and normalization
+
+## Robust Path Handling
+
+One of the first challenges in building a file management tool is handling paths correctly. Here's how I approached it:
+
+```scheme
+(define (expand-home path)
+ "Expand ~ to the user's home directory."
+ (if (string-prefix? "~" path)
+ (string-append (getenv "HOME") (substring path 1))
+ path))
+
+(define (concat-path base path)
+ "Concatenate two paths, ensuring there are no double slashes."
+ (if (string-suffix? "/" base)
+ (string-append (string-drop-right base 1) "/" path)
+ (string-append base "/" path)))
+
+(define (ensure-config-path target-dir)
+ "Ensure that the target directory has .config appended, avoiding double slashes."
+ (let ((target-dir (expand-home target-dir)))
+ (if (string-suffix? "/" target-dir)
+ (set! target-dir (string-drop-right target-dir 1)))
+ (if (not (string-suffix? "/.config" target-dir))
+ (string-append target-dir "/.config")
+ target-dir)))
+```
+
+This approach ensures that:
+- Home directory references (`~`) are properly expanded
+- Path concatenation doesn't create double slashes
+- Configuration paths are consistently structured
+
+## Interactive Conflict Resolution
+
+Real-world tools often need to handle conflicts. I implemented an interactive conflict resolution system:
+
+```scheme
+(define (prompt-user-for-action)
+ "Prompt the user to decide how to handle a conflict: overwrite (o), skip (s), or cancel (c)."
+ (display (color-message
+ "A conflict was detected. Choose action - Overwrite (o), Skip (s), or Cancel (c): "
+ yellow-text))
+ (let ((response (read-line)))
+ (cond
+ ((string-ci=? response "o") 'overwrite)
+ ((string-ci=? response "s") 'skip)
+ ((string-ci=? response "c") 'cancel)
+ (else
+ (display "Invalid input. Please try again.\n")
+ (prompt-user-for-action)))))
+```
+
+This provides a user-friendly interface for resolving conflicts while maintaining data safety.
+
+## Logging for Debugging and Auditing
+
+Proper logging is crucial for debugging and auditing. I implemented a simple but effective logging system:
+
+```scheme
+(define (current-timestamp)
+ "Return the current date and time as a formatted string."
+ (let* ((time (current-time))
+ (seconds (time-second time)))
+ (strftime "%Y-%m-%d-%H-%M-%S" (localtime seconds))))
+
+(define (log-action message)
+ "Log an action with a timestamp to the stash.log file."
+ (let ((log-port (open-file "stash.log" "a")))
+ (display (color-message
+ (string-append "[" (current-timestamp) "] " message)
+ green-text) log-port)
+ (newline log-port)
+ (close-port log-port)))
+```
+
+This logging system:
+- Timestamps each action
+- Uses color coding for better readability
+- Maintains a persistent log file
+- Properly handles file operations
+
+## File Operations with Safety
+
+When dealing with file system operations, safety is paramount. Here's how I handle moving directories:
+
+```scheme
+(define (move-source-to-target source-dir target-dir)
+ "Move the entire source directory to the target directory, ensuring .config in the target path."
+ (let* ((target-dir (ensure-config-path target-dir))
+ (source-dir (expand-home source-dir))
+ (source-name (basename source-dir))
+ (target-source-dir (concat-path target-dir source-name)))
+ (if (not (file-exists? target-dir))
+ (mkdir target-dir #o755))
+ (if (file-exists? target-source-dir)
+ (handle-conflict target-source-dir source-dir delete-directory log-action)
+ (begin
+ (rename-file source-dir target-source-dir)
+ (display (format #f "Moved ~a to ~a\n" source-dir target-source-dir))
+ (log-action (format #f "Moved ~a to ~a" source-dir target-source-dir))))
+ target-source-dir))
+```
+
+This implementation:
+- Ensures paths are properly formatted
+- Creates necessary directories
+- Handles conflicts gracefully
+- Logs all operations
+- Returns the new path for further operations
+
+## Lessons Learned
+
+### What Worked Well
+1. **Modular Design**: Breaking the code into focused modules made it easier to maintain and test
+2. **Functional Approach**: Using pure functions where possible made the code more predictable
+3. **Interactive Interface**: Providing clear user prompts and colored output improved usability
+4. **Robust Logging**: Detailed logging helped with debugging and understanding program flow
+
+### Challenges Faced
+1. **Path Handling**: Dealing with different path formats and edge cases required careful attention
+2. **Error States**: Managing various error conditions while keeping the code clean
+3. **User Interface**: Balancing between automation and user control
+4. **Documentation**: Writing clear documentation that helps users understand the tool
+
+## Moving Forward
+
+Building `stash` has taught me that while functional programming principles are valuable, pragmatism is equally important. The key is finding the right balance between elegant functional code and practical solutions.
+
+## Resources
+
+1. [Guile Manual](https://www.gnu.org/software/guile/manual/)
+2. [My Previous Scheme Journey Post](/content/posts/scheme-journey.html)
+3. [System Crafters Community](https://systemcrafters.net/community)
+4. [Stash on Codeberg](https://codeberg.org/glenneth/stash)
+
+The code examples in this post are from my actual implementation of `stash`. Feel free to explore, use, and improve upon them!
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+ Beyond Theory: Building Practical Tools with Guile Scheme - Glenn Thompson
+
+
+
+
+
+
+
+
+
Beyond Theory: Building Practical Tools with Guile Scheme
+
+
+ •
+ 5 min read
+ •
+ By Glenn Thompson
+
+
+
+
+
Beyond Theory: Building Practical Tools with Guile Scheme
+
Introduction
+
A few months ago, I shared my journey into learning Scheme through building stash, a symlink manager. Since then, I've discovered that the gap between learning Scheme and applying it to real-world problems is where the most valuable lessons emerge. This post explores what I've learned about building practical tools with Guile Scheme, sharing both successes and challenges along the way.
+
The Power of Modular Design
+
One of the most important lessons I learned was the value of modular design. Breaking down a program into focused, single-responsibility modules not only makes the code more maintainable but also helps in reasoning about the program's behavior. Here's how I structured stash:
Modular Design: Breaking the code into focused modules made it easier to maintain and test
+
Functional Approach: Using pure functions where possible made the code more predictable
+
Interactive Interface: Providing clear user prompts and colored output improved usability
+
Robust Logging: Detailed logging helped with debugging and understanding program flow
+
+
Challenges Faced
+
+
Path Handling: Dealing with different path formats and edge cases required careful attention
+
Error States: Managing various error conditions while keeping the code clean
+
User Interface: Balancing between automation and user control
+
Documentation: Writing clear documentation that helps users understand the tool
+
+
Moving Forward
+
Building stash has taught me that while functional programming principles are valuable, pragmatism is equally important. The key is finding the right balance between elegant functional code and practical solutions.
+ With over 20 years in the electrical engineering field, I've had the privilege of working on
+ groundbreaking projects across the Middle East. My journey has been marked by continuous
+ learning, cultural exploration, and technological innovation.
+
+
+ Beyond my professional work, I'm passionate about technology, particularly static site
+ generation, Scheme programming, and tools like GNU Guix and Haunt. This blog is where I
+ share my experiences, insights, and the lessons learned along the way.
+
+
+
+
Areas of Focus
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+
+ Electrical Engineering
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+
+ Static Site Generation
+
+
+
+ Scheme Programming
+
+
+
+ Middle Eastern Culture
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Get in Touch
+
+ Interested in connecting? Feel free to reach out for discussions about technology, engineering,
+ or sharing travel stories.
+