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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>It’s always fun to show non-Smalltalkers some of the
neat stuff one can do with Smalltalk. One of my favorite set of examples
involves #inject:into:.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The canonical example is of course something like `#(8 1 6)
inject: 0 into: [:total :value | total + value].` <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>But you shouldn’t stop there, because a) “the
locals” often have some sort of summation function available in their
favorite language that, they think, “does the same thing,” and b)
because there are many much better examples (and these are good to keep in mind
when coding.) The canonical example is really only useful for explaining the
basic concept (and perhaps clarifying points of Smalltalk syntax and/or
semantics.) Then comes the advanced course:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>1. Concatenation<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> #(‘usr’
‘local’ ‘bin’) inject: ‘’ into: [:path
:suffix | path, ‘/’, suffix].<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>2. Min/max:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> #(9
2 4 12 -3 44) inject: Infinity positive into: [:min :value | value >= min
ifTrue: [min] ifFalse: [value]]<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> #(9
2 4 12 -3 44) inject: Infinity negative into: [:max :value | value <= max
ifTrue: [max] ifFalse: [value]]<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> If
your image doesn’t have Infinity: <o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:.5in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>#(9 2 4 12 -3 44)
inject: nil into: [:min :value | (min == nil or: [value < min]) ifTrue:
[value] ifFalse: [min]]<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>3. Hierarchical path traversal:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> “Note:
this is a really good technique for representing and traversing namespace paths
in a syntax-independent way”<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> #(TextConstants
CR) inject: Smalltalk into: [:poolDictionary :key | poolDictionary at: key]<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> #(HKEY_CURRENT_USER
ENVIRONMENT TZ) <o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:.5in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>inject: WindowsRegistry
current<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:.5in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>into: [:namespace
:key | namespace at: key]<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> |
path |<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>path := #(home alan smalltalk squeak
`3.9’ alan.image) <o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:.5in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>inject: ResourcePath
root<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:.5in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>into: [:path
:suffix | path exists ifFalse: [path makeDirectory]. path, suffix].<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> path
exists ifTrue: [path execute].<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Of course, some of the above examples assume the existence
of certain classes that you probably don’t have in your image. Perhaps
you should…<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>--Alan<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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