RE: why Pi is not recognized as a positive number?

*To*: mathgroup at smc.vnet.net*Subject*: [mg45364] RE: [mg45360] why Pi is not recognized as a positive number?*From*: "David Park" <djmp at earthlink.net>*Date*: Sat, 3 Jan 2004 01:35:07 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Peter, x_Positive is the pattern for an expression that has the Head Positive - not what your want. You want... f[x_?Positive] := x + 1 f[Pi] 1 + Pi David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Pedro L [mailto:pedrito6 at softhome.net] To: mathgroup at smc.vnet.net I wanted to define a function for the positive numbers. But I discovered something "strange" with Mathematica. Could you help me with this? Thanks in advance. Peter L (Spain) { Cell[CellGroupData[{ Cell[BoxData["$Version"], "Input", CellLabel->"In[1]:="], Cell[BoxData["\<\"5.0 for Microsoft Windows (June 11, 2003)\"\>"], \ "Output", CellLabel->"Out[1]="] }, Open ]], Cell[BoxData[ RowBox[{ RowBox[{"f", "[", "x_Positive", "]"}], ":=", RowBox[{"x", "+", "1", " "}]}]], "Input", CellLabel->"In[2]:="], Cell[CellGroupData[{ Cell[BoxData[ RowBox[{"Positive", "[", "Pi", "]"}]], "Input", CellLabel->"In[3]:="], Cell[BoxData["True"], "Output", CellLabel->"Out[3]="] }, Open ]], Cell[CellGroupData[{ Cell[BoxData[ RowBox[{"f", "[", "Pi", "]"}]], "Input", CellLabel->"In[4]:="], Cell[BoxData[ RowBox[{"f", "[", "\[Pi]", "]"}]], "Output", CellLabel->"Out[4]="] }, Open ]], Cell[BoxData[ RowBox[{"Remove", "[", "f", "]"}]], "Input", CellLabel->"In[5]:="], Cell[BoxData[ RowBox[{ RowBox[{"f", "[", RowBox[{"x_", " ", "/;", " ", RowBox[{"x", ">", "0"}]}], "]"}], ":=", RowBox[{"x", "+", "1"}]}]], "Input", CellLabel->"In[6]:="], Cell[CellGroupData[{ Cell[BoxData[ RowBox[{"f", "[", "Pi", "]"}]], "Input", CellLabel->"In[7]:="], Cell[BoxData[ RowBox[{"1", "+", "\[Pi]"}]], "Output", CellLabel->"Out[7]="] }, Open ]], Cell[BoxData[ RowBox[{"Remove", "[", "f", "]"}]], "Input", CellLabel->"In[8]:="] }