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MathGroup Archive 2005

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Re: A ToExpression question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58335] Re: [mg58316] A ToExpression question
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 28 Jun 2005 21:56:35 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

A character embedded in a string is not a symbol.

f1[x_]:=Print[x];
f2[x_]:=ToExpression["Print["<>ToString[x]<>"]"];
f3[x_]:=Module[{y=x},ToExpression["Print["<>ToString[y]<>"]"]];
f4[x_]:=Block[{y=x},ToExpression["Print[y]"]];

Scan[#[0]&,{f1,f2,f3,f4}]


0

0

0

0


Bob Hanlon

> 
> From: "Ray Koopman" <koopman at sfu.ca>
To: mathgroup at smc.vnet.net
> Date: 2005/06/28 Tue AM 05:13:15 EDT
> Subject: [mg58335] [mg58316] A ToExpression question
> 
> f1[x_] := Print[x];
> f2[x_] := ToExpression["Print[x]"];
> f3[x_] := Module[{y = x}, ToExpression["Print[y]"]];
> f4[x_] :=  Block[{y = x}, ToExpression["Print[y]"]];
> 
> Scan[#[0]&,{f1,f2,f3,f4}]
> 
> 0
> x
> y
> 0
> 
> Why don't f2 and f3 print 0 ?
> 
> 


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