65 lines
2.3 KiB
Nim
65 lines
2.3 KiB
Nim
# SPDX-FileCopyrightText: 2021 ☭ Emery Hemingway
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# SPDX-License-Identifier: Unlicense
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import std/[macros, typetraits]
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import ../preserves
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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 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 ``x``.
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when not T.hasCustomPragma(record): {.error: "no {.record.} pragma on " & $T.}
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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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proc classOf*(T: typedesc[tuple]): RecordClass =
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## Derive the ``RecordClass`` of ``T``.
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when not T.hasCustomPragma(record): {.error: "no {.record.} pragma on " & $T.}
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RecordClass(
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label: preserves.symbol(T.getCustomPragmaVal(record)),
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arity: tupleLen(T))
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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, $(fields.toPreserve) & " (arity " & $fields.len & ") is not of arity " & $rec.arity)
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result = initRecord(rec.label, fields)
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proc init*(T: typedesc[tuple]; fields: varargs[Preserve, toPreserve]): Preserve =
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## Initialize a new record value.
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init(classOf(T), fields)
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proc `%`*(rec: RecordClass; fields: openArray[Preserve]): Preserve =
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## Initialize a simple record value.
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init(rec, fields)
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proc `%`*(rec: RecordClass; field: Preserve): Preserve =
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## Initialize a simple record value.
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init(rec, [field])
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proc `%`*[T](rec: RecordClass; field: T): Preserve =
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## Initialize a simple record value.
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init(rec, [toPreserve field])
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proc `%`*(T: typedesc[tuple]; fields: varargs[Preserve, toPreserve]): Preserve =
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## Initialize a new record value.
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`%`(classOf(T), fields)
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