julia-prettyshow: pretty-printing in Julia

This module provides simple pretty printing facilities. So far, there is some base functionality for indentation etc, and a pshow (pretty show) implementation for julia AST:s.
Edit: The AST printing functionality has been simplified and merged into Julia.

Usage

Use pshow,pprint, and pprintln more or less as you would show,print, and println.
A pretty printing context can be given as first argument:

pprint(io::PrettyIO, x)

Automatic indentation is supported by nesting arguments to pprint within vectors. I e

fname = "unnecessarily_long_function_name"
pprintln("for ", {"i=1:n\n", 
             "for ", {"j=1:m\n",
                 "X[",{"i, j"},"] = ",
                     "A[",{"$fname(i)"},"]", " * ",
                     "B[",{"$fname(j)"},"]"
             }, "\nend"
         }, "\nend")

prints

for i=1:n
    for j=1:m
        X[i, j] = A[unnecessarily_long_function_name(i)] * B[
            unnecessarily_long_function_name(j)]
    end
end

By annotating the text with the nesting structure like this, pprint can do the right thing at line breaks, even within the index [$fname(j)]. pprint also tries not to avoid breaking individual strings across lines.

Pretty-printing new types

To implement pretty-printing for a type T, it should be enough to overload

pshow(io::PrettyIO, t::T)

This should output to io using pshow/pprint/pprintln.

For slightly fancier pretty-printing, there is also a newline callback associated with each nested PrettyIO context (see the code). I've used this in another project to implement pretty printing of tree views:

A=CallNode(
 +- .op=SymNode(:+, :call), 
 +- .arg1=CallNode(
 |   +- .op=SymNode(:.*, :call), 
 |   +- .arg1=SymNode(:B, :input), 
 |   \- .arg2=SymNode(:C, :input)), 
 \- .arg2=SymNode(:D, :input))
X=KnotNode(
 +- .pre=A, 
 \- .value=CallNode(
     +- .op=SymNode(:+, :call), 
     +- .arg1=A, 
     \- .arg2=SymNode(:C, :input)))
assign1=AssignNode(
 +- .lhs=RefNode(
 |   +- .ref=SymNode(:dest1, :output), 
 |   \- .ind=SymNode(:..., :symbol)), 
 \- .rhs=A)
assign2=AssignNode(
 +- .lhs=RefNode(
 |   +- .ref=SymNode(:dest2, :output), 
 |   \- .ind=SymNode(:..., :symbol)), 
 \= .rhs=X, .dep=assign1)
sink=TupleNode(
 \= .arg1=assign2, .arg2=X)