Keyword Arguments Implementation for XDL Plot Function

Summary

Implemented full keyword argument support for the plot procedure in XDL, allowing users to specify plot titles and axis labels using keyword syntax.

Changes Made

1. Core Infrastructure (xdl-interpreter)

  • evaluator.rs: Added keyword argument evaluation for both function calls and procedure calls
    • Evaluates Keyword structures from AST
    • Converts evaluated keywords to HashMap<String, XdlValue>
    • Passes keywords to stdlib functions
  • lib.rs: Updated procedure call handling to process keyword arguments
    • Extracts keyword values from AST
    • Calls call_procedure_with_keywords instead of call_procedure

2. Standard Library (xdl-stdlib)

  • lib.rs: Extended StandardLibrary to accept keyword arguments
    • Added call_function_with_keywords method
    • Added call_procedure_with_keywords method
    • Updated PLOT procedure routing to use plot_with_keywords
  • graphics_procs.rs: Implemented plot_with_keywords function
    • Extracts title, xtitle, ytitle keywords (case-insensitive)
    • Creates Plot2DConfig with appropriate settings
    • Passes configuration to plot_2d function

3. Testing

Created test scripts demonstrating the new functionality:

  • test_plot_keywords.xdl: Basic sine wave with titles
  • test_plot_keywords2.xdl: Damped oscillation with different titles

Usage 

; Generate data
x = findgen(100) / 10.0
y = sin(x)

; Plot with keyword arguments
plot, y, x, title='My Plot Title', xtitle='X Axis Label', ytitle='Y Axis Label'

Supported Keywords

  • title / TITLE: Main plot title
  • xtitle / XTITLE: X-axis label
  • ytitle / YTITLE: Y-axis label

Keywords are case-insensitive (both lowercase and uppercase work).

Benefits

  1. User-friendly: Natural syntax matching IDL/GDL conventions
  2. Extensible: Infrastructure supports adding more keywords easily
  3. Backward compatible: Old code without keywords still works
  4. Type-safe: Keyword values are properly validated

Future Enhancements

The keyword argument infrastructure can now be used to add more plotting options:

  • Color selection (color=)
  • Line styles (linestyle=)
  • Symbol types (psym=)
  • Axis ranges (xrange=, yrange=)
  • Background color (background=)
  • And more…

Implementation Notes

  • Keywords in XDL parser were already supported but not implemented in the evaluator
  • The Plot2DConfig structure already had title fields, they just weren’t populated from user input
  • All keyword handling is centralized in the evaluator and stdlib layers