ADDED: library(options) #1134
ADDED: library(options) #1134
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This library is useful mostly in other libraries, to more easily reason about options of various predicates. Currently, the only provided predicate is option/3 to ask for the value of an option, and use a default value if the option is not specified explicitly.
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What happens with an unexpected option? Please note that options have been added in Cor.3. It seems you only support certain instantiation errors. |
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Yes, this is very preliminary currently, limited to selecting the needed option! Type checks for options can be added with suitable declarations, maybe with a second predicate that goes through the options. The check may even be performed statically in some cases, using goal expansion. |
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An example of an |
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So far, options are producing arbitrary type and domain errors, but with an incorrect option, there is only one domain_error(xxx_option,...) the additional in some sense more precise error needs to be caught and then put in the 2nd argument of error/2. |
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OK, I have converted this pull request to a draft for the time being, maybe there is a better or more comprehensive way to solve this. |
mthom
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This library is mostly intended for authors of other libraries. I did not even mention it in the
README, because it only contains a single predicate:option/3, to ask whether an option was specified, obtaining its value, and to use a default if the option is not stated explicitly.Still, I think this is a useful building block, and makes option processing in various libraries easier, more correct, and less error-prone. I have used it in
library(crypto)andlibrary(charsio)to show how it works.