Merge pull request #25 from magistere/deparse

Make 'deparse' function correctly handle parentheses

Author: johnmyleswhite

src/check_derivative.jl

@@ -1,19 +1,19 @@
 function check_derivative(f::Function, g::Function, x::Number)
 	auto_g = derivative(f)
-	return max(abs(g(x) - auto_g(x)))
+	return maximum(abs(g(x) - auto_g(x)))
 end
 
 function check_gradient{T <: Number}(f::Function, g::Function, x::Vector{T})
 	auto_g = gradient(f)
-	return max(abs(g(x) - auto_g(x)))
+	return maximum(abs(g(x) - auto_g(x)))
 end
 
 function check_second_derivative(f::Function, h::Function, x::Number)
 	auto_h = second_derivative(f)
-	return max(abs(h(x) - auto_h(x)))
+	return maximum(abs(h(x) - auto_h(x)))
 end
 
 function check_hessian{T <: Number}(f::Function, h::Function, x::Vector{T})
 	auto_h = hessian(f)
-	return max(abs(h(x) - auto_h(x)))
+	return maximum(abs(h(x) - auto_h(x)))
 end

src/deparse.jl

@@ -1,24 +1,30 @@
+const infix_ops = [:+, :-, :*, :/, :^]
+const op_priority = {:+ => 1, :- => 1, :* => 2, :/ => 2, :^ => 3}
+
+isinfix(ex::Expr) = ex.head == :call && ex.args[1] in infix_ops
+isinfix(other) = false
+
 function deparse(ex::Expr)
     if ex.head != :call
         return string(ex)
-    else
-        if ex.args[1] in [:+, :-, :*, :/, :^]
-            if length(ex.args) == 2
-                return string(ex.args[1], deparse(ex.args[2]))
-            else
-                return join(map(x -> deparse(x), ex.args[2:end]),
-                            string(" ", string(ex.args[1]), " "))
-            end
+    end
+    op = ex.args[1]
+    args = ex.args[2:end]
+    if !(op in infix_ops)
+        return string(op, "(", join(map(deparse, args), ", "), ")")
+    end
+    if length(args) == 1
+        return string(op, deparse(args[1]))
+    end
+    str = {}
+    for subexpr in args
+        if isinfix(subexpr) && op_priority[subexpr.args[1]] <= op_priority[op]
+            push!(str, string("(", deparse(subexpr), ")"))
         else
-            return string(ex.args[1],
-                          "(",
-                          join(map(x -> deparse(x), ex.args[2:end]), ", "),
-                          ")")
+            push!(str, deparse(subexpr))
         end
     end
+    return join(str, string(" ", string(op), " "))
 end
-deparse(other::Any) = string(other)
 
-# TODO: Examine string contents of inputs, insert parentheses if added:
-# + (CONTAINS * OR /)
-# - (CONTAINS * OR /)
+deparse(other) = string(other)

test/deparse.jl

@@ -1,2 +1,8 @@
 @assert isequal(deparse(:(cos(x) + sin(x))), "cos(x) + sin(x)")
 @assert isequal(deparse(:(cos(x) + sin(x) + exp(-x))), "cos(x) + sin(x) + exp(-x)")
+@assert isequal(deparse(parse("x+y*z")), "x + y * z")
+@assert isequal(deparse(parse("(x+y)*z")), "(x + y) * z")
+@assert isequal(deparse(parse("1/(x/y)")), "1 / (x / y)")
+@assert isequal(deparse(parse("1/(x*y)")), "1 / (x * y)")
+@assert isequal(deparse(parse("z^(x+y)")), "z ^ (x + y)")
+@assert isequal(deparse(parse("z^(x*y)")), "z ^ (x * y)")