Although it was never a conscious design goal, during its evolution a wholesome part of Grace proved to actively make C++ look more like Python. I wasn’t even really aware of Python until about two years into the project, so this fact both surprised and inspired me. It surprised me, because I didn’t expect similar efforts towards code legibility to spring out of the corner of a system scripting language — obviously a wrong way to look at things, but after seeing Tcl, Perl and PHP at work my cynical heart had grown weary. It is inspiring to know that there are people out there with similar ideas and vision and that their ideas are capable of growing a following. Ever since, I’ve been using Python as a reflective surface when evaluating potential new constructs in Grace.
I’ve never been envious of Python. I’m rational enough to just forget about it all and join the dark side if that’s ever going to happen. I was, however, particularily fond of the Python command line interpreter. Of course this idea has been around since the invention of, well, the shell, but one thing it accomplishes is that it allows you to quickly try out the effects of different commands and constructs without opening a text editor. This is a place where compiled languages tend to suck.
This week, Peter lamented the absence of this feature as well. He mumbled something about ‘just feed it through gcc’ and probably expected that to be the end of it. So last night I built a Grace shell. It uses some awfully tacky hacks to do its business, but I didn’t even have enough time to accumulate my distaste for that once I started noticing how completely addictive working with it is. It takes away a lot of anxiety that would normally have you running for the documentation by letting you just explore what happens when you call an API function.
Here’s the shell in action, working out the value class:
>>> value p
>>> p = $("name","John Doe")->$("mail","j@doe.org")
>>> p["url"] = "http://doe.org/~j/"
>>> print (p.toxml())
<?xml version="1.0" encoding="UTF-8"?>
<dict id="person">
<string id="name">John Doe</string>
<string id="mail">j@doe.org</string>
<string id="url">http://doe.org/~j/</string>
</dict>
>>> foreach (f,p){
> print ("%10s : %s" %format (f.id(),f))
> }
name : John Doe
mail : j@doe.org
url : http://doe.org/~j/
The shell already exposed a number of bugs that would’ve taken much longer to get themselves caught otherwise. People with access to our mercurial repo can find gracesh in /hg/.