From 13b79fe04bfeda5a544a35d949e4b2929db42529 Mon Sep 17 00:00:00 2001
From: Dahua Lin <lindahua@gmail.com>
Date: Fri, 31 Oct 2014 15:40:58 +0800
Subject: [PATCH] new implementation of `show` for distributions

---
 src/multivariate/dirichlet.jl |   2 +
 src/multivariate/mvnormal.jl  |   3 +
 src/show.jl                   | 101 +++++++++++++++++++++-------------
 3 files changed, 67 insertions(+), 39 deletions(-)

diff --git a/src/multivariate/dirichlet.jl b/src/multivariate/dirichlet.jl
index 0d6335e82..ae46bebc4 100644
--- a/src/multivariate/dirichlet.jl
+++ b/src/multivariate/dirichlet.jl
@@ -32,6 +32,8 @@ length(d::DirichletCanon) = length(d.alpha)
 Base.convert(::Type{Dirichlet}, cf::DirichletCanon) = Dirichlet(cf.alpha)
 
 
+Base.show(io::IO, d::Dirichlet) = show(io, d, (:alpha,))
+
 # Properties
 
 length(d::Dirichlet) = length(d.alpha)
diff --git a/src/multivariate/mvnormal.jl b/src/multivariate/mvnormal.jl
index f38120dbb..eb4b666ea 100644
--- a/src/multivariate/mvnormal.jl
+++ b/src/multivariate/mvnormal.jl
@@ -28,6 +28,9 @@ function GenericMvNormal{Cov<:AbstractPDMat}(Σ::Cov)
     GenericMvNormal{Cov}(d, true, zeros(d), Σ)    
 end
 
+Base.show(io::IO, d::GenericMvNormal) = 
+    show_multline(io, d, [(:dim, d.dim), (:μ, mean(d)), (:Σ, cov(d))])
+
 ## Construction of multivariate normal with specific covariance type
 
 typealias IsoNormal  GenericMvNormal{ScalMat}
diff --git a/src/show.jl b/src/show.jl
index 26f902f32..665b4b889 100644
--- a/src/show.jl
+++ b/src/show.jl
@@ -1,48 +1,71 @@
-function show(io::IO, d::Distribution)
-    @printf io "%s distribution\n" typeof(d)
-    for parameter in typeof(d).names
-        if isa(d.(parameter), AbstractArray)
-            param = string(ucfirst(string(parameter)),
-                           ":\n",
-                           d.(parameter),
-                           "\n")
-        else
-            param = string(ucfirst(string(parameter)),
-                           ": ",
-                           d.(parameter),
-                           "\n")
+
+
+# the name of a distribution
+#
+#   Generally, this should be just the type name, e.g. Normal.
+#   Under certain circumstances, one may want to specialize
+#   this function to provide a name that is easier to read, 
+#   especially when the type is parametric. 
+#
+distrname(d::Distribution) = string(typeof(d))
+
+show(io::IO, d::Distribution) = show(io, d, typeof(d).names)
+
+# For some distributions, the fields may contain internal details,
+# which we don't want to show, this function allows one to 
+# specify which fields to show.
+#
+function show(io::IO, d::Distribution, pnames::(Symbol...))
+    # decide whether to use one-line or multi-line format
+    #
+    # Criteria: if total number of values is greater than 8, or
+    # there are matrix-valued params, we use multi-line format
+    #
+    namevals = (Symbol, Any)[]
+    multline = false
+    tlen = 0
+    for (i, p) in enumerate(pnames)
+        pv = d.(p)
+        if !(isa(pv, Number) || isa(pv, (Number...)) || isa(pv, AbstractVector))
+            multline = true
         end
-        print(io, param)
+        tlen += length(pv)
+        push!(namevals, (p, pv))
+    end
+    if tlen > 8
+        multline = true
     end
+
+    # call the function that actually does the job
+    multline ? show_multline(io, d, namevals) :
+               show_oneline(io, d, namevals)
 end
 
-function compact_show(io::IO, d::Distribution)
-    print(io, typeof(d))
-    print(io, "( ")
-    for parameter in typeof(d).names
-        print(io, string(parameter))
-        print(io, "=")
-        pv = d.(parameter)
-        if isa(pv, AbstractVector)
-            print(io, '[')
-            if !isempty(pv)
-                for i = 1 : length(pv)-1
-                    print(io, pv[i])
-                    print(io, ", ")
-                end
-                print(io, pv[end])
-            end
-            print(io, ']')
-        else
-            print(io, pv)
-        end 
-        print(io, " ")         
-    end        
-    print(io, ")")  
+function show_oneline(io::IO, d::Distribution, namevals)
+    print(io, distrname(d))
+    np = length(namevals)
+    print(io, '(')
+    for (i, nv) in enumerate(namevals)
+        (p, pv) = nv
+        print(io, p)
+        print(io, '=')
+        show(io, pv)
+        if i < np
+            print(io, ", ")
+        end
+    end
+    print(io, ')')
 end
 
-function show(io::IO, d::UnivariateDistribution)
-    compact_show(io, d)
+function show_multline(io::IO, d::Distribution, namevals)
+    print(io, distrname(d))
+    println(io, "(")
+    for (p, pv) in namevals
+        print(io, p)
+        print(io, ": ")
+        println(io, pv)
+    end
+    println(io, ")")
 end