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52 lines
1.4 KiB
OpenEdge ABL
52 lines
1.4 KiB
OpenEdge ABL
[Certainty::] Adverbs of Certainty.
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To represent levels of certainty.
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@h Scale of certainties.
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Inform uses the following scale to measure how certain it is that something
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is true:
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@d IMPOSSIBLE_CE -2
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@d UNLIKELY_CE -1
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@d UNKNOWN_CE 0
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@d LIKELY_CE 1
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@d CERTAIN_CE 2
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@ A special certainty level is used for a temporal sense of certainty:
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@d INITIALLY_CE 3
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@ Certainty adverbs are found mainly in regular sentences:
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>> A door is usually open.
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They are syntactically legal in existential sentences too, though in
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English this usually expresses emphasis rather than a measure of
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probability: consider "there certainly are men in the room". Inform allows
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this, in any case.
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Note that no adverb corresponds to the |UNKNOWN_CE| certainty level, which
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expresses no information.
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The use of certainty adverbs is a point of difference between Inform's two
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grammars. In assertions one can write
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>> A box is usually closed. (1)
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but in conditions one can't write
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>> if a box is usually closed, ... (2)
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This is because (1) is essentially a statement about the future, not the
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present or the past, whereas conditions like (2) must always be determinable at
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once: Inform cannot know what will generally happen, only what is now the case
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and what has been the case in the past.
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=
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<certainty> ::=
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always/certainly | ==> CERTAIN_CE
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usually/normally | ==> LIKELY_CE
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rarely/seldom | ==> UNLIKELY_CE
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never | ==> IMPOSSIBLE_CE
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initially ==> INITIALLY_CE
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