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:.

 

The canonical example is of course something like `#(8 1 6) inject: 0 into:
[:total :value | total + value].` 

 

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:

 

1. Concatenation

 

            #('usr' 'local' 'bin') inject: '' into: [:path :suffix | path,
'/', suffix].

 

2. Min/max:

 

            #(9 2 4 12 -3 44) inject: Infinity positive into: [:min :value |
value >= min ifTrue: [min] ifFalse: [value]]

            #(9 2 4 12 -3 44) inject: Infinity negative into: [:max :value |
value <= max ifTrue: [max] ifFalse: [value]]

 

            If your image doesn't have Infinity: 

#(9 2 4 12 -3 44) inject: nil into: [:min :value | (min == nil or: [value <
min]) ifTrue: [value] ifFalse: [min]]

 

3. Hierarchical path traversal:

            "Note: this is a really good technique for representing and
traversing namespace paths in a syntax-independent way"

 

            #(TextConstants CR) inject: Smalltalk into: [:poolDictionary
:key | poolDictionary at: key]

 

            #(HKEY_CURRENT_USER ENVIRONMENT TZ) 

inject: WindowsRegistry current

into: [:namespace :key | namespace at: key]

 

            | path |

path := #(home alan smalltalk squeak `3.9' alan.image) 

inject: ResourcePath root

into: [:path :suffix | path exists ifFalse: [path makeDirectory]. path,
suffix].

            path exists ifTrue: [path execute].

 

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.

 

--Alan

 

 

 

 

 

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