Boolean

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(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 of these objects print with those names.
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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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? true
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== Protocol ==
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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>.
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=== pick/2 ===
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== Protocol ==
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pick(<var>t</var>, <var>f</var>) :any
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{{instance msgdoc|pick|2|<var>t</var>, <var>f</var>|any}}
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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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=== not/0 ===
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# value: 1
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not() :Boolean
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? false.pick(3, 4)
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# value: 4
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{{instance msgdoc|not|0||[[Boolean]]}}
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Boolean negation.
Boolean negation.
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? !true
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=== or/1 ===
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# value: false
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? !false
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# value: true
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{{instance msgdoc|or|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
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or(<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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=== and/1 ===
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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
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{{instance msgdoc|and|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
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and(<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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=== xor/1 ===
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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
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xor(<var>other</var> :Boolean) :Boolean
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{{instance msgdoc|xor|1|<var>other</var> :[[Boolean]]|[[Boolean]]}}
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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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=== op__cmp/1 ===
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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
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=== 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
 
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[[Category:ELib specification]]
 

Revision as of 19:47, 21 April 2007

The Boolean type has exactly two members, false and true. All three names are in the universal scope.

Contents

Protocol

pick/2

pick(t, f) :any

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

not/0

not() :Boolean

Boolean negation.

or/1

or(other :Boolean) :Boolean

Boolean or. The argument is coerced to a boolean.

and/1

and(other :Boolean) :Boolean

Boolean and. The argument is coerced to a boolean.

xor/1

xor(other :Boolean) :Boolean

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

op__cmp/1

Comparison with other Booleans. See Message op__cmp.

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