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Add a way to specify how a field should be parsed and formatted
We need a way to specify "format a month as a name" and "format a month as a number without padding." The new `FieldFormatDirective` interface encodes this concept.
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‎core/common/src/internal/format/FieldFormatDirective.kt

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/*
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* Copyright 2019-2023 JetBrains s.r.o. and contributors.
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* Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
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*/
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package kotlinx.datetime.internal.format
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import kotlinx.datetime.internal.DecimalFraction
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import kotlinx.datetime.internal.format.formatter.*
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import kotlinx.datetime.internal.format.parser.*
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/**
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* A directive that specifies a way to parse and format the [field].
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*/
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internal interface FieldFormatDirective<in Target> {
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/**
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* The field parsed and formatted by this directive.
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*/
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val field: FieldSpec<Target, *>
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/**
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* The formatter operation that formats the field.
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*/
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fun formatter(): FormatterStructure<Target>
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/**
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* The parser structure that parses the field.
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*/
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fun parser(): ParserStructure<Target>
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}
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/**
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* A directive for a decimal format of an integer field that is known to be unsigned.
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* The field is formatted with the field padded to [minDigits] with zeroes,
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* and the parser expects the field to be at least [minDigits] digits long.
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*/
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internal abstract class UnsignedIntFieldFormatDirective<in Target>(
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final override val field: UnsignedFieldSpec<Target>,
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private val minDigits: Int,
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private val spacePadding: Int?,
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) : FieldFormatDirective<Target> {
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private val maxDigits: Int = field.maxDigits
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init {
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require(minDigits >= 0) {
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"The minimum number of digits ($minDigits) is negative"
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}
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require(maxDigits >= minDigits) {
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"The maximum number of digits ($maxDigits) is less than the minimum number of digits ($minDigits)"
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}
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if (spacePadding != null) {
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require(spacePadding > minDigits) {
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"The space padding ($spacePadding) should be more than the minimum number of digits ($minDigits)"
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}
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}
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}
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override fun formatter(): FormatterStructure<Target> {
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val formatter = UnsignedIntFormatterStructure(
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number = field.accessor::getterNotNull,
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zeroPadding = minDigits,
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)
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return if (spacePadding != null) SpacePaddedFormatter(formatter, spacePadding) else formatter
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}
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override fun parser(): ParserStructure<Target> =
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spaceAndZeroPaddedUnsignedInt(minDigits, maxDigits, spacePadding, field.accessor, field.name)
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}
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/**
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* A directive for a string-based format of an integer field that is known to be unsigned.
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*/
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internal abstract class NamedUnsignedIntFieldFormatDirective<in Target>(
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final override val field: UnsignedFieldSpec<Target>,
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private val values: List<String>,
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private val name: String,
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) : FieldFormatDirective<Target> {
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init {
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require(values.size == field.maxValue - field.minValue + 1) {
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"The number of values (${values.size}) in $values does not match the range of the field (${field.maxValue - field.minValue + 1})"
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}
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}
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private fun getStringValue(target: Target): String = field.accessor.getterNotNull(target).let {
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values.getOrNull(it-field.minValue)
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?: "The value $it of ${field.name} does not have a corresponding string representation"
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}
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private inner class AssignableString: AssignableField<Target, String> {
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override fun trySetWithoutReassigning(container: Target, newValue: String): String? =
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field.accessor.trySetWithoutReassigning(container, values.indexOf(newValue) + field.minValue)?.let {
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values[it - field.minValue]
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}
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override val name: String get() = this@NamedUnsignedIntFieldFormatDirective.name
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}
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override fun formatter(): FormatterStructure<Target> =
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StringFormatterStructure(::getStringValue)
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override fun parser(): ParserStructure<Target> =
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ParserStructure(
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listOf(
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StringSetParserOperation(values, AssignableString(), "One of $values for $name")
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), emptyList()
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)
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}
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/**
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* A directive for a string-based format of an enum field.
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*/
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internal abstract class NamedEnumIntFieldFormatDirective<in Target, Type>(
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final override val field: FieldSpec<Target, Type>,
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private val mapping: Map<Type, String>,
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private val name: String,
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) : FieldFormatDirective<Target> {
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private val reverseMapping = mapping.entries.associate { it.value to it.key }
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private fun getStringValue(target: Target): String = field.accessor.getterNotNull(target).let {
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mapping[field.accessor.getterNotNull(target)]
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?: "The value $it of ${field.name} does not have a corresponding string representation"
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}
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private inner class AssignableString: AssignableField<Target, String> {
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override fun trySetWithoutReassigning(container: Target, newValue: String): String? =
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field.accessor.trySetWithoutReassigning(container, reverseMapping[newValue]!!)?.let { mapping[it] }
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override val name: String get() = this@NamedEnumIntFieldFormatDirective.name
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}
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override fun formatter(): FormatterStructure<Target> =
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StringFormatterStructure(::getStringValue)
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override fun parser(): ParserStructure<Target> =
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ParserStructure(
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listOf(
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StringSetParserOperation(mapping.values, AssignableString(), "One of ${mapping.values} for $name")
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), emptyList()
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)
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}
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internal abstract class StringFieldFormatDirective<in Target>(
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final override val field: FieldSpec<Target, String>,
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private val acceptedStrings: Set<String>,
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) : FieldFormatDirective<Target> {
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init {
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require(acceptedStrings.isNotEmpty()) {
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"The set of accepted strings is empty"
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}
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}
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override fun formatter(): FormatterStructure<Target> =
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StringFormatterStructure(field.accessor::getterNotNull)
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override fun parser(): ParserStructure<Target> =
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ParserStructure(
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listOf(StringSetParserOperation(acceptedStrings, field.accessor, field.name)),
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emptyList()
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)
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}
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internal abstract class SignedIntFieldFormatDirective<in Target>(
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final override val field: FieldSpec<Target, Int>,
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private val minDigits: Int?,
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private val maxDigits: Int?,
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private val spacePadding: Int?,
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private val outputPlusOnExceededWidth: Int?,
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) : FieldFormatDirective<Target> {
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init {
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require(minDigits == null || minDigits >= 0) { "The minimum number of digits ($minDigits) is negative" }
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require(maxDigits == null || minDigits == null || maxDigits >= minDigits) {
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"The maximum number of digits ($maxDigits) is less than the minimum number of digits ($minDigits)"
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}
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}
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override fun formatter(): FormatterStructure<Target> {
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val formatter = SignedIntFormatterStructure(
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number = field.accessor::getterNotNull,
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zeroPadding = minDigits ?: 0,
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outputPlusOnExceededWidth = outputPlusOnExceededWidth,
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)
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return if (spacePadding != null) SpacePaddedFormatter(formatter, spacePadding) else formatter
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}
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override fun parser(): ParserStructure<Target> =
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SignedIntParser(
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minDigits = minDigits,
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maxDigits = maxDigits,
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spacePadding = spacePadding,
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field.accessor,
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field.name,
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plusOnExceedsWidth = outputPlusOnExceededWidth,
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)
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}
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internal abstract class DecimalFractionFieldFormatDirective<in Target>(
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final override val field: FieldSpec<Target, DecimalFraction>,
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private val minDigits: Int,
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private val maxDigits: Int,
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private val zerosToAdd: List<Int>,
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) : FieldFormatDirective<Target> {
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override fun formatter(): FormatterStructure<Target> =
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DecimalFractionFormatterStructure(field.accessor::getterNotNull, minDigits, maxDigits, zerosToAdd)
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override fun parser(): ParserStructure<Target> = ParserStructure(
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listOf(
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NumberSpanParserOperation(
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listOf(FractionPartConsumer(minDigits, maxDigits, field.accessor, field.name))
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)
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),
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emptyList()
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)
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}
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internal abstract class ReducedIntFieldDirective<in Target>(
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final override val field: FieldSpec<Target, Int>,
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private val digits: Int,
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private val base: Int,
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) : FieldFormatDirective<Target> {
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override fun formatter(): FormatterStructure<Target> =
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ReducedIntFormatterStructure(
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number = field.accessor::getterNotNull,
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digits = digits,
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base = base,
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)
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override fun parser(): ParserStructure<Target> =
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ReducedIntParser(digits = digits, base = base, field.accessor, field.name)
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}

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