diff options
| -rw-r--r-- | HACKING | 48 | ||||
| -rw-r--r-- | README.md | 25 |
2 files changed, 67 insertions, 6 deletions
@@ -0,0 +1,48 @@ + +### Problems With Python/Julia Syntax Mapping with dot ('.') Operator + +*aka, why the annoying underscore syntax is needed* + +Using PyCall, we can map python modules to Julia modules with the same syntax: + + python> import os + python> os.uname() + python> os.O_RDONLY + + julia> using PyCall + julia> os = pywrap(pyimport("os")) + julia> os.uname() + julia> os.O_RDONLY + +And using a recursive version of pywrap (`pyrecwrap`), we can get nested +modules to map also: + + python> import os + python> os.path.genericpath.os.uname() + + julia> os = pyrecwrap(pyimport("os")) + julia> os.path.genericpath.os.uname() + +We can also map python classes to Julia modules: + + python> import pyx.style.linewidth as psl + python> psl.THICK + + julia> ps = pywrap(pyimport("pyx.style")) + julia> psl = pywrap(ps.linewidth) + julia> psl.THICK + +However, in Python a class/object can both have members and be called as an +initializer: + + python> psl.THIN + python> psl(0.1) + +But in Julia a Module can't act as a function. + +Thus, a one-to-one syntax mapping just isn't going to work until (unless?) the +dot ('.') operator can be overridden (as of Julia 0.4 it may not). + +The work around used in this project (PyX.jl) is to use underscores in +object/function names and dots in object/module names. Eg, +`style.linewidth(0.2)` vs. `style_linewidth.THICK`. @@ -74,12 +74,25 @@ All the expected [Julia/Python differences][1] apply: Note that the string code snippets that go into `graph_data_function` are still Python code, not Julia. -There doesn't seem to be an easy way to handle nested Python modules as nested -modules in Julia, so there can only be a single `.` separator in variable and -function names. This has been worked around by using the underscore character -(`_`) instead of `.` for all but the last separator. So, eg, -`graph_axis.split()` instead of `graph.axis.split()` and `color_rgb.red` -instead of `color.rgb.red`. +Because the Python syntax features for objects (they can both be accessed like +a module or called like a function) does not map to any Julia type at this +time, a naming convention is used such that only a single `.` separator is used +in Julia names and calls, and underscore characters (`_`) are used in +objects-as-modules to access attributes. For example: + + python> from pyx import style, color, graph + python> style.linewidth.THICK + python> style.linewidth(0.5) + python> color.rgb.red + python> graph.axis.split() + + julia> using PyX + julia> style_linewidth.THICK + julia> style.linewidth(0.5) + julia> color_rgb.red + julia> graph_axis.split() + +See HACKING for more details. To avoid namespace collisions or confusion with built-in Julia functions the following functions (only) have `pyx_` preprended to the function name: |