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MathGroup Archive 2001

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Re: scope all wrong? in Mathematica 4.1

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31887] Re: scope all wrong? in Mathematica 4.1
  • From: "Alan Mason" <swt at austin.rr.com>
  • Date: Sun, 9 Dec 2001 06:07:12 -0500 (EST)
  • References: <9ul2ft$6m3$1@smc.vnet.net> <9uqa42$ah0$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hello All.
The following notebook has been instrumented to reveal the origin of the
mysterious print statements for Fateman's third example.  Looks like Allan
Hayes is right -- it seems that evaluation is being triggered in an attempt
to sort out possible effects of the previous rules on the one currently
being defined.  Can WR confirm this and elaborate on just how SetDelayed
works?

In[1]:=
Module[{x},
  uu[x_?((Print["Initially, x is ", {x, Hold[x]}];x = 5; Print["x is ", x];
              True) &)] := x;
Print["in Module, x is " , x]]


in Module, x is \[InvisibleSpace]x$9

In[2]:=
?uu

Global`uu

\!\(\*
  InterpretationBox[GridBox[{
        {GridBox[{
              {\(uu[
                    x_?\((\((Print["Initially, x is ", {x$9, Hold[x$9]}];
                            x$9 = 5; Print["x is ", x$9]; True)\) &)\)] :=
                  x\)}
              },
            GridBaseline->{Baseline, {1, 1}},
            ColumnWidths->0.999,
            ColumnAlignments->{Left}]}
        },
      GridBaseline->{Baseline, {1, 1}},
      ColumnAlignments->{Left}],
    Definition[ "uu"],
    Editable->False]\)

In[3]:=
x$9 = 9

Out[3]=
9

In[4]:=
Module[{x},
  uu[x_?((Print["Initially, x is ", {x, Hold[x]}];x = 5; Print["x is ", x];
              True) &)] := x;
Print["in Module, x is " , x]]

Initially, x is \[InvisibleSpace]{9,Hold[x$9]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{x$20,Hold[x$20]}

x is \[InvisibleSpace]5

in Module, x is \[InvisibleSpace]5

In[5]:=
x$9

Out[5]=
5

In[6]:=
?uu

Global`uu

\!\(\*
  InterpretationBox[GridBox[{
        {GridBox[{
              {\(uu[
                    x_?\((\((Print["Initially, x is ", {x$9, Hold[x$9]}];
                            x$9 = 5; Print["x is ", x$9]; True)\) &)\)] :=
                  x\)},
              {" "},
              {\(uu[
                    x_?\((\((Print["Initially, x is ", {x$20, Hold[x$20]}];
                            x$20 = 5; Print["x is ", x$20]; True)\) &)\)] :=
                  x\)}
              },
            GridBaseline->{Baseline, {1, 1}},
            ColumnWidths->0.999,
            ColumnAlignments->{Left}]}
        },
      GridBaseline->{Baseline, {1, 1}},
      ColumnAlignments->{Left}],
    Definition[ "uu"],
    Editable->False]\)

In[7]:=
x$9 = 9;x$20 = 20;

In[8]:=
Module[{x},
  uu[x_?((Print["Initially, x is ", {x, Hold[x]}];x = 5; Print["x is ", x];
              True) &)] := x;
Print["in Module, x is " , x]]

Initially, x is \[InvisibleSpace]{9,Hold[x$9]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{x$24,Hold[x$24]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{20,Hold[x$20]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{5,Hold[x$24]}

x is \[InvisibleSpace]5

in Module, x is \[InvisibleSpace]5

In[9]:=
?uu

Global`uu

\!\(\*
  InterpretationBox[GridBox[{
        {GridBox[{
              {\(uu[
                    x_?\((\((Print["Initially, x is ", {x$9, Hold[x$9]}];
                            x$9 = 5; Print["x is ", x$9]; True)\) &)\)] :=
                  x\)},
              {" "},
              {\(uu[
                    x_?\((\((Print["Initially, x is ", {x$20, Hold[x$20]}];
                            x$20 = 5; Print["x is ", x$20]; True)\) &)\)] :=
                  x\)},
              {" "},
              {\(uu[
                    x_?\((\((Print["Initially, x is ", {x$24, Hold[x$24]}];
                            x$24 = 5; Print["x is ", x$24]; True)\) &)\)] :=
                  x\)}
              },
            GridBaseline->{Baseline, {1, 1}},
            ColumnWidths->0.999,
            ColumnAlignments->{Left}]}
        },
      GridBaseline->{Baseline, {1, 1}},
      ColumnAlignments->{Left}],
    Definition[ "uu"],
    Editable->False]\)

In[10]:=
x$9 = 9;x$20 = 20;x$24=24;

In[11]:=
Module[{x},
  uu[x_?((Print["Initially, x is ", {x, Hold[x]}];x = 5; Print["x is ", x];
              True) &)] := x;
Print["in Module, x is " , x]]

Initially, x is \[InvisibleSpace]{9,Hold[x$9]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{x$28,Hold[x$28]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{20,Hold[x$20]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{5,Hold[x$28]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{24,Hold[x$24]}

x is \[InvisibleSpace]5

Initially, x is \[InvisibleSpace]{5,Hold[x$28]}

x is \[InvisibleSpace]5

in Module, x is \[InvisibleSpace]5



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