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- -- card: 16414 from stack: in
- -- bmap block id: 16755
- -- flags: 4000
- -- background id: 7992
- -- name: 3-Operands
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- -- part 1 (field)
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- -- high flags: 0007
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- -- part 3 (button)
- -- low flags: 00
- -- high flags: 0000
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- -- part name: Next
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- -- part contents for card part 1
- ----- text -----
- The BNF for operands is as follows:
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- operand := [#]FACT fact_id |
- global_id |
- real_number |
- integer |
- boolean |
- quoted_string |
- simple_string |
- "?" | ? | "*" | * | ""
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- Operands are evaluated as follows:
-
- [#]FACT fact_id -- a fact. ex. FACT "fact 1". If the immediate
- -- operator (#) is used, the fact will be
- -- used as is. In other words, the
- -- inference engine will not try to find
- -- a value for a fact that is not asserted
- -- when evaluating the clause.
- global_id -- the value of a global (must have
- -- been declared global)
- real_number -- a real number. ex. 1.5
- integer -- an integer number. ex. 11
- boolean -- either TRUE or FALSE
- quoted_string -- a quoted string. ex. "this is a string"
- simple_string -- a simple string. ex. string1 (no spaces allowed)
- "?" or ? -- "unknown" if applied to a fact (fact will evaluate
- -- false unless compared equal to unknown).
- -- Otherwise, considered a string.
- "*" or * -- "don't care" if applied to a fact or compared
- -- to a fact (fact will always evaluate true).
- -- Otherwise, considered a string.
- "" -- "not asserted" if applied to a fact (fact will be
- -- considered not-asserted). Otherwise,
- -- considered a null string.
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