53 lines
1.8 KiB
Nim
53 lines
1.8 KiB
Nim
# SPDX-License-Identifier: ISC
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import std/[macros, typetraits]
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import ../preserves
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proc initRecord*(label: Preserve; args: varargs[Preserve, toPreserve]): Preserve =
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## Record constructor.
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result = Preserve(kind: pkRecord,
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record: newSeqOfCap[Preserve](1+args.len))
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for arg in args:
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assertValid(arg)
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result.record.add(arg)
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result.record.add(label)
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proc initRecord*(label: string; args: varargs[Preserve, toPreserve]): Preserve {.inline.} =
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## Record constructor that converts ``label`` to a symbol.
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initRecord(symbol(label), args)
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type RecordClass* = object
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## Type of a preserves record.
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label*: Preserve
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arity*: Natural
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proc `$`*(rec: RecordClass): string =
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$rec.label & "/" & $rec.arity
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proc init*(rec: RecordClass; fields: varargs[Preserve, toPreserve]): Preserve =
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## Initialize a new record value.
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assert(fields.len == rec.arity)
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result = initRecord(rec.label, fields)
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proc isClassOf*(rec: RecordClass; val: Preserve): bool =
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## Compare the label and arity of ``val`` to the record type ``rec``.
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if val.kind == pkRecord:
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assert(val.record.len > 0)
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result = val.label == rec.label and rec.arity == val.arity
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proc classOf*(val: Preserve): RecordClass =
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## Derive the ``RecordClass`` of ``val``.
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if val.kind != pkRecord:
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raise newException(Defect, "cannot derive class of non-record value " & $val)
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assert(val.record.len > 0)
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RecordClass(label: val.label, arity: val.arity)
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proc classOf*[T](x: T): RecordClass =
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## Derive the ``RecordClass`` of ``T``.
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# TODO: would be nice to get the class of a type without an instance.
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when not T.hasCustomPragma(record):
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raise newException(Defect, "{.record: \"…\".} must be present to determine classOf")
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else:
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result.label = preserves.symbol(T.getCustomPragmaVal(record))
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for k, v in x.fieldPairs: inc(result.arity)
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