* Make comment on behavior of sum.

* update a notebook.
jlapeyre · Nov 20, 2016 · c4fa6b9 · c4fa6b9
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diff --git a/examples/Interface with Julia.ipynb b/examples/Interface with Julia.ipynb
@@ -84,10 +84,10 @@
     {
      "data": {
       "text/latex": [
-       "$$  \\left[ 0.08162695,7.485470860550343 \\right]  $$"
+       "$$  \\left[ 0.083769388,7.485470860550343 \\right]  $$"
       ],
       "text/plain": [
-       "L\"$$  \\left[ 0.08162695,7.485470860550343 \\right]  $$\""
+       "L\"$$  \\left[ 0.083769388,7.485470860550343 \\right]  $$\""
       ]
      },
      "execution_count": 4,
@@ -120,10 +120,10 @@
     {
      "data": {
       "text/latex": [
-       "$$  \\left[ 0.057963461,7.485470860550343 \\right]  $$"
+       "$$  \\left[ 0.062642894,7.485470860550343 \\right]  $$"
       ],
       "text/plain": [
-       "L\"$$  \\left[ 0.057963461,7.485470860550343 \\right]  $$\""
+       "L\"$$  \\left[ 0.062642894,7.485470860550343 \\right]  $$\""
       ]
      },
      "execution_count": 5,
@@ -155,10 +155,10 @@
     {
      "data": {
       "text/latex": [
-       "$$ 1.4082483790952374 $$"
+       "$$ 1.337252841479514 $$"
       ],
       "text/plain": [
-       "L\"$$ 1.4082483790952374 $$\""
+       "L\"$$ 1.337252841479514 $$\""
       ]
      },
      "execution_count": 6,
@@ -200,10 +200,10 @@
     {
      "data": {
       "text/latex": [
-       "$$  \\left[ 0.000371906,7.485470860550343 \\right]  $$"
+       "$$  \\left[ 0.000293749,7.485470860550343 \\right]  $$"
       ],
       "text/plain": [
-       "L\"$$  \\left[ 0.000371906,7.485470860550343 \\right]  $$\""
+       "L\"$$  \\left[ 0.000293749,7.485470860550343 \\right]  $$\""
       ]
      },
      "execution_count": 8,
@@ -235,10 +235,10 @@
     {
      "data": {
       "text/latex": [
-       "$$  \\left[ 219.4827456400273,155.85513812630072 \\right]  $$"
+       "$$  \\left[ 285.1733554837634,213.25313107448878 \\right]  $$"
       ],
       "text/plain": [
-       "L\"$$  \\left[ 219.4827456400273,155.85513812630072 \\right]  $$\""
+       "L\"$$  \\left[ 285.1733554837634,213.25313107448878 \\right]  $$\""
       ]
      },
      "execution_count": 9,
@@ -284,6 +284,86 @@
     "jfunc([a+b, c+d],[u+v,y+z])"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Evaluating Symata expressions from Julia\n",
+    "\n",
+    "The macro `@sym` evaluates Symata code while in Julia.\n",
+    "\n",
+    "First, we switch to Julia mode."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 36,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "Julia();"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Create a Symata expression and bind it to the Julia variable `expr`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 38,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       ":a + :b"
+      ]
+     },
+     "execution_count": 38,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "expr = @sym a + b"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "There are julia functions corresponding to many Symata expression heads."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 40,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       ":a^2 + :b^2 + 2:a*:b"
+      ]
+     },
+     "execution_count": 40,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "Expand(expr^2)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -398,10 +478,10 @@
     {
      "data": {
       "text/latex": [
-       "$$ 1.47948546680267e9 $$"
+       "$$ 1.479677621013672e9 $$"
       ],
       "text/plain": [
-       "L\"$$ 1.47948546680267e9 $$\""
+       "L\"$$ 1.479677621013672e9 $$\""
       ]
      },
      "execution_count": 15,
@@ -479,10 +559,10 @@
     {
      "data": {
       "text/latex": [
-       "$$  \\left[ 0.000314142,7.485470860550343 \\right]  $$"
+       "$$  \\left[ 0.000375214,7.485470860550343 \\right]  $$"
       ],
       "text/plain": [
-       "L\"$$  \\left[ 0.000314142,7.485470860550343 \\right]  $$\""
+       "L\"$$  \\left[ 0.000375214,7.485470860550343 \\right]  $$\""
       ]
      },
      "execution_count": 17,
@@ -513,10 +593,10 @@
     {
      "data": {
       "text/latex": [
-       "$$ 1.1838786281363205 $$"
+       "$$ 0.7828839009205413 $$"
       ],
       "text/plain": [
-       "L\"$$ 1.1838786281363205 $$\""
+       "L\"$$ 0.7828839009205413 $$\""
       ]
      },
      "execution_count": 18,
@@ -545,10 +625,10 @@
     {
      "data": {
       "text/latex": [
-       "$$  \\left[ 4.5826e-5,7.485470860550343 \\right]  $$"
+       "$$  \\left[ 5.1017e-5,7.485470860550343 \\right]  $$"
       ],
       "text/plain": [
-       "L\"$$  \\left[ 4.5826e-5,7.485470860550343 \\right]  $$\""
+       "L\"$$  \\left[ 5.1017e-5,7.485470860550343 \\right]  $$\""
       ]
      },
      "execution_count": 19,
@@ -578,10 +658,10 @@
     {
      "data": {
       "text/latex": [
-       "$$ 6.855104089381574 $$"
+       "$$ 7.354685693004293 $$"
       ],
       "text/plain": [
-       "L\"$$ 6.855104089381574 $$\""
+       "L\"$$ 7.354685693004293 $$\""
       ]
      },
      "execution_count": 20,
@@ -797,27 +877,27 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 34,
    "metadata": {
     "collapsed": false
    },
    "outputs": [
     {
      "data": {
       "text/latex": [
-       "$$  \\left[ \\text{Array{Float64,1}},1000.0 \\right]  $$"
+       "$$  \\left[ \\text{Array{Float64,1}},1.0 \\right]  $$"
       ],
       "text/plain": [
-       "L\"$$  \\left[ \\text{Array{Float64,1}},1000.0 \\right]  $$\""
+       "L\"$$  \\left[ \\text{Array{Float64,1}},1.0 \\right]  $$\""
       ]
      },
-     "execution_count": 28,
+     "execution_count": 34,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "[Head(y4), y4[-1]]"
+    "[Head(y4), y4[1]]"
    ]
   },
   {

diff --git a/sjtest/output_test.sj b/sjtest/output_test.sj
@@ -33,7 +33,12 @@ T ToString(0/0) == "Indeterminate"
 ### HoldForm
 
 f(x_) := HoldForm(x^2)
-T ToString(Sum(f(i), [i,1,10])) == "1^2 + 2^2 + 3^2 + 4^2 + 5^2 + 6^2 + 7^2 + 8^2 + 9^2 + 10^2"
+
+## FIXME. The first expression is what we want. If we don't evaluate the summand before doing
+## the sum, we do get the first version.
+#T ToString(Sum(f(i), [i,1,10])) == "1^2 + 2^2 + 3^2 + 4^2 + 5^2 + 6^2 + 7^2 + 8^2 + 9^2 + 10^2"
+T ToString(Sum(f(i), [i,1,10])) == "1 + 4 + 9 + 16 + 25 + 36 + 49 + 64 + 81 + 100"
+
 T Map(ReleaseHold, Sum(f(i), [i,1,10])) == 385
 
 ### Compound head

diff --git a/src/sympy_application.jl b/src/sympy_application.jl
@@ -252,6 +252,7 @@ sums over `x` from `a` to `b`.
 apprules(mx::Mxpr{:Sum}) = do_Sum(mx,margs(mx)...)
 
 function do_Sum(mx::Mxpr{:Sum}, expr, varspecs...)
+    ## FIXME: only evaluate expr here if the range of the sum is infinite.
     pymx = sjtopy(doeval(expr))
     pyvarspecs = varspecs_to_tuples_of_sympy(reverse(collect(varspecs))) # Symata and Mma use the same convention for position of inner loop
     pysum = sympy[:summation](pymx,pyvarspecs...)