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57 lines
1.7 KiB
OpenEdge ABL
57 lines
1.7 KiB
OpenEdge ABL
[Certainty::] Adverbs of Certainty.
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Adverbs such as "usually" or "initially".
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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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@ =
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void Certainty::write(OUTPUT_STREAM, int level) {
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switch (level) {
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case IMPOSSIBLE_CE: WRITE("impossible"); break;
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case UNLIKELY_CE: WRITE("unlikely"); break;
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case UNKNOWN_CE: WRITE("(no certainty level)"); break;
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case LIKELY_CE: WRITE("likely"); break;
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case CERTAIN_CE: WRITE("certain"); break;
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case INITIALLY_CE: WRITE("initial"); break;
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}
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}
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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 English
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this usually expresses emphasis rather than a measure of probability: consider
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"there certainly are men in the room". Inform allows this, in any case. In
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conditions, Inform is more picky. For example, 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: run-time code cannot know what will generally happen, only what is now
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the case 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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