Boolean

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(use instance msgdoc template)
(copy in tests from E-on-CL scope-univ.updoc r1044)
 
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The '''<code>Boolean</code>''' type has exactly two members, <code>false</code> and <code>true</code>. All three names are in the [[universal scope]].
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The '''<code>Boolean</code>''' type has exactly two members, <code>false</code> and <code>true</code>. All three of these objects print with those names.
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? true
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# value: true
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? false
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# value: false
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? boolean
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# value: Boolean
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The [[universal scope]] contains <code>boolean</code> (no capital), <code>false</code>, and <code>true</code>.
== Protocol ==
== Protocol ==
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false.pick(<var>t</var>, <var>f</var>) returns <var>f</var>; true.pick(<var>t</var>, <var>f</var>) returns <var>t</var>.
false.pick(<var>t</var>, <var>f</var>) returns <var>f</var>; true.pick(<var>t</var>, <var>f</var>) returns <var>t</var>.
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? true.pick(1, 2)
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# value: 1
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? false.pick(3, 4)
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# value: 4
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{{instance msgdoc|not|0||[[Boolean]]}}
{{instance msgdoc|not|0||[[Boolean]]}}
Boolean negation.
Boolean negation.
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? !true
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# value: false
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? !false
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# value: true
{{instance msgdoc|or|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
{{instance msgdoc|or|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
Boolean or. The argument is coerced to a boolean.
Boolean or. The argument is coerced to a boolean.
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? false | false
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# value: false
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? false | true
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# value: true
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? false | def _{to __conformTo(==boolean) :any {return false}}
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# value: false
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? true | false
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# value: true
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? true | true
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# value: true
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? true | -1
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# problem: the int -1 doesn't coerce to a boolean
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? true | def _{to __conformTo(==boolean) :any {return true}}
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# value: true
{{instance msgdoc|and|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
{{instance msgdoc|and|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
Boolean and. The argument is coerced to a boolean.
Boolean and. The argument is coerced to a boolean.
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? true & true
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# value: true
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? true & false
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# value: false
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? true & def _{to __conformTo(==boolean) :any {return true}}
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# value: true
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? false & true
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# value: false
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? false & false
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# value: false
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? false & -1
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# problem: the int -1 doesn't coerce to a boolean
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? false & def _{to __conformTo(==boolean) :any {return false}}
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# value: false
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{{XXX}} discuss ideal default wording of coercion failure errors
{{instance msgdoc|xor|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
{{instance msgdoc|xor|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
Boolean exclusive or. The argument is coerced to a boolean.
Boolean exclusive or. The argument is coerced to a boolean.
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? false ^ false
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# value: false
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? false ^ true
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# value: true
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? true ^ def _{to __conformTo(==boolean) :any {return true}}
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# value: false
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? true ^ false
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# value: true
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? true ^ true
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# value: false
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? false ^ -1
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# problem: the int -1 doesn't coerce to a boolean
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? false ^ def _{to __conformTo(==boolean) :any {return true}}
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# value: true
=== op__cmp/1 ===
=== op__cmp/1 ===
Comparison with other Booleans. See [[Message op__cmp]].
Comparison with other Booleans. See [[Message op__cmp]].
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{{XXX}} write tests for this
[[Category:ELib specification]]
[[Category:ELib specification]]

Latest revision as of 22:58, 10 January 2009

The Boolean type has exactly two members, false and true. All three of these objects print with those names. 

? true
# value: true

? false
# value: false

? boolean
# value: Boolean

The universal scope contains boolean (no capital), false, and true.

Contents

Protocol

pick/2

Signature: pick(t, f) :any

false.pick(t, f) returns f; true.pick(t, f) returns t. 

? true.pick(1, 2)
# value: 1

? false.pick(3, 4)
# value: 4

not/0

Signature: not() :Boolean

Boolean negation. 

? !true
# value: false

? !false
# value: true

or/1

Signature: or(other :Boolean) :Boolean

Boolean or. The argument is coerced to a boolean. 

? false | false
# value: false

? false | true
# value: true

? false | def _{to __conformTo(==boolean) :any {return false}}
# value: false

? true | false
# value: true

? true | true
# value: true

? true | -1
# problem: the int -1 doesn't coerce to a boolean

? true | def _{to __conformTo(==boolean) :any {return true}}
# value: true

and/1

Signature: and(other :Boolean) :Boolean

Boolean and. The argument is coerced to a boolean. 

? true & true
# value: true

? true & false
# value: false

? true & def _{to __conformTo(==boolean) :any {return true}}
# value: true

? false & true
# value: false

? false & false
# value: false

? false & -1
# problem: the int -1 doesn't coerce to a boolean

? false & def _{to __conformTo(==boolean) :any {return false}}
# value: false

XXX discuss ideal default wording of coercion failure errors

xor/1

Signature: xor(other :Boolean) :Boolean

Boolean exclusive or. The argument is coerced to a boolean. 

? false ^ false
# value: false

? false ^ true
# value: true

? true ^ def _{to __conformTo(==boolean) :any {return true}}
# value: false

? true ^ false
# value: true

? true ^ true
# value: false

? false ^ -1
# problem: the int -1 doesn't coerce to a boolean

? false ^ def _{to __conformTo(==boolean) :any {return true}}
# value: true

op__cmp/1

Comparison with other Booleans. See Message op__cmp.

XXX write tests for this

Retrieved from "http://wiki.erights.org/wiki/Boolean"
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