/usr/share/gnu-smalltalk/examples/Case.st is in gnu-smalltalk-common 3.2.5-1build2.
This file is owned by root:root, with mode 0o644.
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| Case syntax for Smalltalk
|
|
======================================================================"
"======================================================================
|
| Written by Ulf Dambacher.
|
| This file is part of GNU Smalltalk.
|
| GNU Smalltalk is free software; you can redistribute it and/or modify it
| under the terms of the GNU General Public License as published by the Free
| Software Foundation; either version 2, or (at your option) any later version.
|
| GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT
| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
| FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
| details.
|
| You should have received a copy of the GNU General Public License along with
| GNU Smalltalk; see the file COPYING. If not, write to the Free Software
| Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
|
======================================================================"
Object subclass: #Case
instanceVariableNames: 'test found result'
classVariableNames: ''
poolDictionaries: ''
category: 'Examples-Useful tools'
!
Case comment:
'A nice class for switch-like tests. Slower than cascaded ifs but clearer.
#case:do: uses identity for testing (useful since you''ll likely use Case
with symbols, integers, characters, and the like), #ifEqualTo:do: uses
equality.
e.g.
Case new test: myObject;
case: 5 do: [ ''got five'' printNl ];
when: [ :testVal | testVal isInteger ] do: [ ''an integer'' printNl ];
else: [ :testVal | testVal printNl ]
You can use (Case test: myObject) instead of the first line above. Which of
the two possibilities is clearer, it is a matter of taste.'!
!Case class methodsFor: 'instance creation'!
test: anObject
^self new test: anObject
! !
!Case methodsFor: 'testing'!
test: anObject
test := anObject.
found := false.
!
reset
found := false
!
else: aBlock
^found
ifFalse: [ self do: aBlock ]
ifTrue: [ result ].
!
case: anObject do: aBlock
^(found not and: [test == anObject])
ifTrue: [ self do: aBlock ]
ifFalse: [ result ].
!
ifEqualTo: anObject do: aBlock
^(found not and: [test = anObject])
ifTrue: [ self do: aBlock ]
ifFalse: [ result ].
!
when: aBlock do: aBlock2
^(found not and: [aBlock value: test])
ifTrue: [ self do: aBlock ]
ifFalse: [ result ].
! !
!Case methodsFor: 'private'!
do: aBlock
found := true.
^result := (aBlock cull: test)
! !
Object subclass: #Switch
instanceVariableNames: 'values defaultBlock'
classVariableNames: ''
poolDictionaries: ''
category: 'Examples-Useful tools'
!
Object subclass: #SwitchCase
instanceVariableNames: 'secondParameter evaluationBlock actionBlock result'
classVariableNames: ''
poolDictionaries: ''
category: 'Examples-Useful tools'
!
Switch comment:
'Another class for switch-like tests. This is reusable, i.e. an instance
stores its case-do pairs.
e.g.
(Switch new)
case: "value or Block" do: [...];
...
default: [...];
on: value. "#= equality matching of cases"
(Switch new)
case: "value or Block" do: [...];
...
default: [...];
exactlyOn: value. "#== identity matching of cases"
'!
!Switch class methodsFor: 'instance creation'!
new
^self basicNew values: (ReadWriteStream on: Array new: 5)
! !
!Switch methodsFor: 'initialization'!
values: aStream
values := aStream
!
default: aBlock
defaultBlock := aBlock
!
case: anObjectOrBlock do: aBlock
| block |
block := anObjectOrBlock class == BlockClosure
ifTrue: [
[ :object :block :identity | block value: object ]
ifFalse: [
[ :object :comparison :identity |
identity
ifTrue: [ object == comparison ]
ifFalse: [ object = comparison ]
]
].
values nextPut: (SwitchCase new
secondParameter: anObjectOrBlock
evaluationBlock: block
actionBlock: aBlock)
! !
!Switch methodsFor: 'evaluation'!
on: anObject
| done case |
done := false.
values reset.
[ values atEnd ] whileFalse: [
case := values next.
(case evaluateIfEqualTo: anObject) ifTrue: [ ^case result ].
].
^defaultBlock value! !
exactlyOn: anObject
| done case |
done := false.
values reset.
[ values atEnd ] whileFalse: [
case := values next.
(case evaluateIfIdenticalTo: anObject) ifTrue: [ ^case result ].
].
^defaultBlock value! !
identityOn: anObject
| done case |
done := false.
values reset.
[ values atEnd ] whileFalse: [
case := values next.
(case evaluateIfIdenticalTo: anObject) ifTrue: [ ^case result ].
].
^defaultBlock value! !
!SwitchCase methodsFor: 'evaluation'!
evaluateIfEqualTo: object
^(evaluationBlock value: object value: secondParameter value: false)
ifTrue: [ result := actionBlock value ];
yourself
!
evaluateIfIdenticalTo: object
^(evaluationBlock value: object value: secondParameter value: true)
ifTrue: [ result := actionBlock value ];
yourself
!
result
| answer |
answer := result.
result := nil.
^answer
! !
!SwitchCase methodsFor: 'initialization'!
secondParameter: sP evaluationBlock: eB actionBlock: aB
secondParameter := sP.
evaluationBlock := eB.
actionBlock := aB
! !
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