POC: scientific notation

core/src/ast.rs

@@ -706,6 +706,9 @@ fn evaluate_as<I: Interrupt>(
 			Value::Sf => {
 				return Err(FendError::SpecifyNumSf);
 			}
+			Value::Sn => {
+				return Err(FendError::SpecifyNumSn);
+			}
 			Value::Base(base) => Value::Num(Box::new(
 				evaluate(a, scope, attrs, spans, context, int)?
 					.expect_num()?
@@ -765,6 +768,7 @@ pub(crate) fn resolve_identifier<I: Interrupt>(
 	lowercase_builtin_result.or(unit_result)
 }
 
+#[allow(clippy::too_many_lines)]
 fn resolve_builtin_identifier<I: Interrupt>(
 	ident: &Ident,
 	scope: Option<Arc<Scope>>,
@@ -847,6 +851,7 @@ fn resolve_builtin_identifier<I: Interrupt>(
 		"float" => Value::Format(FormattingStyle::ExactFloat),
 		"dp" => Value::Dp,
 		"sf" => Value::Sf,
+		"sn" => Value::Sn,
 		"base" => Value::BuiltInFunction(BuiltInFunction::Base),
 		"dec" | "decimal" => Value::Base(Base::from_plain_base(10)?),
 		"hex" | "hexadecimal" => Value::Base(Base::from_plain_base(16)?),

core/src/error.rs

@@ -38,12 +38,14 @@ pub(crate) enum FendError {
 	InvalidDiceSyntax,
 	SpecifyNumDp,
 	SpecifyNumSf,
+	SpecifyNumSn,
 	UnableToInvertFunction(&'static str),
 	InvalidOperandsForSubtraction,
 	InversesOfLambdasUnsupported,
 	CouldNotFindKeyInObject,
 	CouldNotFindKey(String),
 	CannotFormatWithZeroSf,
+	CannotFormatWithZeroSn,
 	UnableToGetCurrentDate,
 	IsNotAFunction(String),
 	IsNotAFunctionOrNumber(String),
@@ -150,6 +152,9 @@ impl fmt::Display for FendError {
 				f,
 				"you need to specify what number of significant figures to use, e.g. '10 sf'"
 			),
+			Self::SpecifyNumSn => {
+				write!(f, "you need to specify what precision to use, e.g. '10 sn'")
+			}
 			Self::ExpectedAUnitlessNumber => write!(f, "expected a unitless number"),
 			Self::ExpectedARealNumber => write!(f, "expected a real number"),
 			Self::StringCannotBeLonger => write!(f, "string cannot be longer than one codepoint"),
@@ -189,6 +194,12 @@ impl fmt::Display for FendError {
 			Self::CannotFormatWithZeroSf => {
 				write!(f, "cannot format a number with zero significant figures")
 			}
+			Self::CannotFormatWithZeroSn => {
+				write!(
+					f,
+					"cannot format a number with zero precision in scientific notation"
+				)
+			}
 			Self::IsNotAFunction(s) => write!(f, "'{s}' is not a function"),
 			Self::IsNotAFunctionOrNumber(s) => write!(f, "'{s}' is not a function or number"),
 			Self::IdentifierNotFound(s) => write!(f, "unknown identifier '{s}'"),

core/src/num/base.rs

@@ -25,6 +25,14 @@ enum BaseEnum {
 
 impl Base {
 	pub(crate) const HEX: Self = Self(BaseEnum::Hex);
+	#[cfg(test)]
+	pub(crate) const OCT: Self = Self(BaseEnum::Octal);
+	#[cfg(test)]
+	pub(crate) const BIN: Self = Self(BaseEnum::Binary);
+
+	pub(crate) const fn is_plain(self) -> bool {
+		matches!(self.0, BaseEnum::Plain(_))
+	}
 
 	pub(crate) const fn base_as_u8(self) -> u8 {
 		match self.0 {
@@ -35,6 +43,14 @@ impl Base {
 		}
 	}
 
+	pub(crate) const fn max_value(self) -> u8 {
+		self.base_as_u8() - 1
+	}
+
+	pub(crate) const fn max_char(self) -> char {
+		Self::digit_as_char(self.max_value() as _).expect("Max value is valid")
+	}
+
 	pub(crate) const fn from_zero_based_prefix_char(ch: char) -> FResult<Self> {
 		Ok(match ch {
 			'x' => Self(BaseEnum::Hex),
@@ -62,7 +78,7 @@ impl Base {
 		Ok(Self(BaseEnum::Custom(base)))
 	}
 
-	pub(crate) fn write_prefix(self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+	pub(crate) fn write_prefix(self, f: &mut impl fmt::Write) -> Result<(), fmt::Error> {
 		match self.0 {
 			BaseEnum::Binary => write!(f, "0b")?,
 			BaseEnum::Octal => write!(f, "0o")?,