wip: fix(dsl): maybe getting somewhere?

dsl/src/ast.rs

@@ -1,31 +1,38 @@
+//! The abstract syntax tree (AST) can be produced from the CST
+//! by cloning source slices into owned ([Arc]) string slices.
 use crate::*;
 
 #[derive(Debug, Clone, Default, PartialEq)]
-pub struct Ast(pub AstValue);
+pub struct Ast(pub Arc<VecDeque<DslVal<Arc<str>, Ast>>>);
 
-/// The abstract syntax tree (AST) can be produced from the CST
-/// by cloning source slices into owned [Arc] values.
-pub type AstValue = DslValue<Arc<str>, VecDeque<Ast>>;
-
-//#[derive(Debug, Clone, Default, PartialEq)]
-//pub struct AstIter();
-
-impl<'src> From<Cst<'src>> for Ast {
-    fn from (token: Cst<'src>) -> Self {
-        token.value().into()
+impl Dsl for Ast {
+    type Str = Arc<str>;
+    type Exp = Ast;
+    fn nth (&self, index: usize) -> Option<DslVal<Self::Str, Self::Exp>> {
+        self.0.get(index).cloned()
     }
 }
 
-impl<'src> From<CstValue<'src>> for Ast {
-    fn from (value: CstValue<'src>) -> Self {
-        Self(match value {
-            DslValue::Nil       => DslValue::Nil,
-            DslValue::Err(e)    => DslValue::Err(e),
-            DslValue::Num(u)    => DslValue::Num(u),
-            DslValue::Sym(s)    => DslValue::Sym(s.into()),
-            DslValue::Key(s)    => DslValue::Key(s.into()),
-            DslValue::Str(s)    => DslValue::Str(s.into()),
-            DslValue::Exp(d, x) => DslValue::Exp(d, x.map(|x|x.into()).collect()),
-        })
+impl<'s> From<Cst<'s>> for Ast {
+    fn from (cst: Cst<'s>) -> Self {
+        Self(VecDeque::from([dsl_val(cst.val())]).into())
+    }
+}
+
+impl<'s> From<CstIter<'s>> for Ast {
+    fn from (cst: CstIter<'s>) -> Self {
+        Self(cst.map(|x|x.value.into()).collect::<VecDeque<_>>().into())
+    }
+}
+
+impl<'s> From<CstVal<'s>> for Ast {
+    fn from (cst: CstVal<'s>) -> Self {
+        Self(VecDeque::from([dsl_val(cst.val())]).into())
+    }
+}
+
+impl<'s> From<DslVal<&'s str, CstIter<'s>>> for DslVal<Arc<str>, Ast> {
+    fn from (cst: DslVal<&'s str, CstIter<'s>>) -> Self {
+        dsl_val(cst)
     }
 }

dsl/src/cst.rs

@@ -1,9 +1,219 @@
 //! The concrete syntax tree (CST) implements zero-copy
 //! parsing of the DSL from a string reference. CST items
 //! preserve info about their location in the source.
-
 use crate::*;
 
+/// CST stores strings as source references and expressions as [CstIter] instances.
+#[derive(Debug, Clone, Default, PartialEq)]
+pub struct Cst<'src>(pub CstIter<'src>);
+impl<'src> Dsl for Cst<'src> {
+    type Str = &'src str;
+    type Exp = CstIter<'src>;
+    fn nth (&self, index: usize) -> Option<DslVal<Self::Str, Self::Exp>> {
+        self.0.nth(index)
+    }
+}
+
+/// Parsed substring with range and value.
+#[derive(Debug, Copy, Clone, Default, PartialEq)]
+pub struct CstVal<'src> {
+    /// Meaning of token.
+    pub value:  DslVal<&'src str, CstIter<'src>>,
+    /// Reference to source text.
+    pub source: &'src str,
+    /// Index of 1st character of token.
+    pub start:  usize,
+    /// Length of token.
+    pub length: usize,
+}
+impl<'src> Dsl for CstVal<'src> {
+    type Str = &'src str;
+    type Exp = CstIter<'src>;
+    fn nth (&self, index: usize) -> Option<DslVal<Self::Str, Self::Exp>> {
+        todo!()
+    }
+}
+
+impl<'src> CstVal<'src> {
+    pub const fn new (
+        source: &'src str,
+        start:  usize,
+        length: usize,
+        value:  DslVal<&'src str, CstIter<'src>>
+    ) -> Self {
+        Self { source, start, length, value }
+    }
+    pub const fn end (&self) -> usize {
+        self.start.saturating_add(self.length)
+    }
+    pub const fn slice (&'src self) -> &'src str {
+        self.slice_source(self.source)
+    }
+    pub const fn slice_source <'range> (&'src self, source: &'range str) -> &'range str {
+        str_range(source, self.start, self.end())
+    }
+    pub const fn slice_source_exp <'range> (&'src self, source: &'range str) -> &'range str {
+        str_range(source, self.start.saturating_add(1), self.end())
+    }
+    pub const fn with_value (self, value: DslVal<&'src str, CstIter<'src>>) -> Self {
+        Self { value, ..self }
+    }
+    pub const fn value (&self) -> DslVal<&'src str, CstIter<'src>> {
+        self.value
+    }
+    pub const fn error (self, error: DslErr) -> Self {
+        Self { value: DslVal::Err(error), ..self }
+    }
+    pub const fn grow (self) -> Self {
+        Self { length: self.length.saturating_add(1), ..self }
+    }
+    pub const fn grow_num (self, m: usize, c: char) -> Self {
+        match to_digit(c) {
+            Result::Ok(n)  => Self { value: DslVal::Num(10*m+n), ..self.grow() },
+            Result::Err(e) => Self { value: DslVal::Err(e),      ..self.grow() },
+        }
+    }
+    pub const fn grow_key (self) -> Self {
+        let token = self.grow();
+        token.with_value(DslVal::Key(token.slice_source(self.source)))
+    }
+    pub const fn grow_sym (self) -> Self {
+        let token = self.grow();
+        token.with_value(DslVal::Sym(token.slice_source(self.source)))
+    }
+    pub const fn grow_str (self) -> Self {
+        let token = self.grow();
+        token.with_value(DslVal::Str(token.slice_source(self.source)))
+    }
+    pub const fn grow_exp (self) -> Self {
+        let token = self.grow();
+        if let DslVal::Exp(depth, _) = token.value() {
+            token.with_value(DslVal::Exp(depth, CstIter::new(token.slice_source_exp(self.source))))
+        } else {
+            unreachable!()
+        }
+    }
+    pub const fn grow_in (self) -> Self {
+        let token = self.grow_exp();
+        if let DslVal::Exp(depth, source) = token.value() {
+            token.with_value(DslVal::Exp(depth.saturating_add(1), source))
+        } else {
+            unreachable!()
+        }
+    }
+    pub const fn grow_out (self) -> Self {
+        let token = self.grow_exp();
+        if let DslVal::Exp(depth, source) = token.value() {
+            if depth > 0 {
+                token.with_value(DslVal::Exp(depth - 1, source))
+            } else {
+                return self.error(Unexpected(')'))
+            }
+        } else {
+            unreachable!()
+        }
+    }
+}
+
+/// Provides a native [Iterator] API over [CstConstIter],
+/// emitting [Cst] items.
+///
+/// [Cst::next] returns just the [Cst] and mutates `self`,
+/// instead of returning an updated version of the struct as [CstConstIter::next] does.
+#[derive(Copy, Clone, Debug, Default, PartialEq)]
+pub struct CstIter<'src>(pub CstConstIter<'src>);
+impl<'src> Dsl for CstIter<'src> {
+    type Str = &'src str;
+    type Exp = Self;
+    fn nth (&self, index: usize) -> Option<DslVal<Self::Str, Self::Exp>> {
+        use DslVal::*;
+        self.0.nth(index).map(|x|match x {
+            Nil => Nil,
+            Err(e) => Err(e),
+            Num(u) => Num(u),
+            Sym(s) => Sym(s),
+            Key(s) => Sym(s),
+            Str(s) => Sym(s),
+            Exp(d, x) => DslVal::Exp(d, CstIter(x)),
+        })
+    }
+}
+impl<'src> CstIter<'src> {
+    pub const fn new (source: &'src str) -> Self {
+        Self(CstConstIter::new(source))
+    }
+    pub const fn peek (&self) -> Option<CstVal<'src>> {
+        self.0.peek()
+    }
+}
+impl<'src> Iterator for CstIter<'src> {
+    type Item = CstVal<'src>;
+    fn next (&mut self) -> Option<CstVal<'src>> {
+        self.0.next().map(|(item, rest)|{
+            self.0 = rest;
+            item
+        })
+    }
+}
+impl<'src> Into<Vec<CstVal<'src>>> for CstIter<'src> {
+    fn into (self) -> Vec<CstVal<'src>> {
+        self.collect()
+    }
+}
+impl<'src> Into<Vec<Ast>> for CstIter<'src> {
+    fn into (self) -> Vec<Ast> {
+        self.map(Into::into).collect()
+    }
+}
+
+/// Owns a reference to the source text.
+/// [CstConstIter::next] emits subsequent pairs of:
+/// * a [Cst] and
+/// * the source text remaining
+///   * [ ] TODO: maybe [CstConstIter::next] should wrap the remaining source in `Self` ?
+#[derive(Copy, Clone, Debug, Default, PartialEq)]
+pub struct CstConstIter<'src>(pub &'src str);
+impl<'src> Dsl for CstConstIter<'src> {
+    type Str = &'src str;
+    type Exp = Self;
+    fn nth (&self, mut index: usize) -> Option<DslVal<Self::Str, Self::Exp>> {
+        use DslVal::*;
+        let mut iter = self.clone();
+        for i in 0..index {
+            iter = iter.next()?.1
+        }
+        iter.next().map(|(x, _)|match x.value {
+            Nil => Nil,
+            Err(e) => Err(e),
+            Num(u) => Num(u),
+            Sym(s) => Sym(s),
+            Key(s) => Sym(s),
+            Str(s) => Sym(s),
+            Exp(d, x) => DslVal::Exp(d, x.0),
+        })
+    }
+}
+impl<'src> CstConstIter<'src> {
+    pub const fn new (source: &'src str) -> Self {
+        Self(source)
+    }
+    pub const fn chomp (&self, index: usize) -> Self {
+        Self(split_at(self.0, index).1)
+    }
+    pub const fn next (mut self) -> Option<(CstVal<'src>, Self)> {
+        Self::next_mut(&mut self)
+    }
+    pub const fn peek (&self) -> Option<CstVal<'src>> {
+        peek_src(self.0)
+    }
+    pub const fn next_mut (&mut self) -> Option<(CstVal<'src>, Self)> {
+        match self.peek() {
+            Some(token) => Some((token, self.chomp(token.end()))),
+            None => None
+        }
+    }
+}
+
 /// Implement the const iterator pattern.
 macro_rules! const_iter {
     ($(<$l:lifetime>)?|$self:ident: $Struct:ty| => $Item:ty => $expr:expr) => {
@@ -19,6 +229,10 @@ macro_rules! const_iter {
     }
 }
 
+const_iter!(<'src>|self: CstConstIter<'src>|
+    => CstVal<'src>
+    => self.next_mut().map(|(result, _)|result));
+
 /// Static iteration helper used by [cst].
 macro_rules! iterate {
     ($expr:expr => $arg: pat => $body:expr) => {
@@ -30,140 +244,26 @@ macro_rules! iterate {
     }
 }
 
-/// CST stores strings as source references and expressions as [SourceIter] instances.
-pub type CstValue<'source> = DslValue<&'source str, SourceIter<'source>>;
-
-/// Token sharing memory with source reference.
-#[derive(Debug, Copy, Clone, Default, PartialEq)]
-pub struct Cst<'src> {
-    /// Reference to source text.
-    pub source: &'src str,
-    /// Index of 1st character of token.
-    pub start:  usize,
-    /// Length of token.
-    pub length: usize,
-    /// Meaning of token.
-    pub value:  CstValue<'src>,
-}
-
-impl<'src> Cst<'src> {
-    pub const fn new (
-        source: &'src str,
-        start:  usize,
-        length: usize,
-        value:  CstValue<'src>
-    ) -> Self {
-        Self { source, start, length, value }
-    }
-    pub const fn end (&self) -> usize {
-        self.start.saturating_add(self.length)
-    }
-    pub const fn slice (&'src self) -> &'src str {
-        self.slice_source(self.source)
-    }
-    pub const fn slice_source <'range> (&'src self, source: &'range str) -> &'range str {
-        str_range(source, self.start, self.end())
-    }
-    pub const fn slice_source_exp <'range> (&'src self, source: &'range str) -> &'range str {
-        str_range(source, self.start.saturating_add(1), self.end())
-    }
-    pub const fn with_value (self, value: CstValue<'src>) -> Self {
-        Self { value, ..self }
-    }
-    pub const fn value (&self) -> CstValue<'src> {
-        self.value
-    }
-    pub const fn error (self, error: DslError) -> Self {
-        Self { value: DslValue::Err(error), ..self }
-    }
-    pub const fn grow (self) -> Self {
-        Self { length: self.length.saturating_add(1), ..self }
-    }
-    pub const fn grow_num (self, m: usize, c: char) -> Self {
-        match to_digit(c) {
-            Result::Ok(n)  => Self { value: DslValue::Num(10*m+n), ..self.grow() },
-            Result::Err(e) => Self { value: DslValue::Err(e),      ..self.grow() },
-        }
-    }
-    pub const fn grow_key (self) -> Self {
-        let token = self.grow();
-        token.with_value(DslValue::Key(token.slice_source(self.source)))
-    }
-    pub const fn grow_sym (self) -> Self {
-        let token = self.grow();
-        token.with_value(DslValue::Sym(token.slice_source(self.source)))
-    }
-    pub const fn grow_str (self) -> Self {
-        let token = self.grow();
-        token.with_value(DslValue::Str(token.slice_source(self.source)))
-    }
-    pub const fn grow_exp (self) -> Self {
-        let token = self.grow();
-        if let DslValue::Exp(depth, _) = token.value() {
-            token.with_value(DslValue::Exp(depth, SourceIter::new(token.slice_source_exp(self.source))))
-        } else {
-            unreachable!()
-        }
-    }
-    pub const fn grow_in (self) -> Self {
-        let token = self.grow_exp();
-        if let DslValue::Exp(depth, source) = token.value() {
-            token.with_value(DslValue::Exp(depth.saturating_add(1), source))
-        } else {
-            unreachable!()
-        }
-    }
-    pub const fn grow_out (self) -> Self {
-        let token = self.grow_exp();
-        if let DslValue::Exp(depth, source) = token.value() {
-            if depth > 0 {
-                token.with_value(DslValue::Exp(depth - 1, source))
-            } else {
-                return self.error(Unexpected(')'))
-            }
-        } else {
-            unreachable!()
-        }
-    }
-}
-
-pub const fn to_number (digits: &str) -> DslResult<usize> {
-    let mut value = 0;
-    iterate!(char_indices(digits) => (_, c) => match to_digit(c) {
-        Ok(digit) => value = 10 * value + digit,
-        Result::Err(e) => return Result::Err(e)
-    });
-    Ok(value)
-}
-
-pub const fn to_digit (c: char) -> DslResult<usize> {
-    Ok(match c {
-        '0' => 0, '1' => 1, '2' => 2, '3' => 3, '4' => 4,
-        '5' => 5, '6' => 6, '7' => 7, '8' => 8, '9' => 9,
-        _ => return Result::Err(Unexpected(c))
-    })
-}
-
-pub const fn peek_src <'src> (source: &'src str) -> Option<Cst<'src>> {
-    use DslValue::*;
-    let mut token: Cst<'src> = Cst::new(source, 0, 0, Nil);
+pub const fn peek_src <'src> (source: &'src str) -> Option<CstVal<'src>> {
+    use DslVal::*;
+    let mut token: CstVal<'src> = CstVal::new(source, 0, 0, Nil);
     iterate!(char_indices(source) => (start, c) => token = match token.value() {
         Err(_) => return Some(token),
         Nil => match c {
             ' '|'\n'|'\r'|'\t' =>
                 token.grow(),
             '(' =>
-                Cst::new(source, start, 1, Exp(1, SourceIter::new(str_range(source, start, start + 1)))),
+                CstVal::new(source, start, 1, Exp(1, CstIter::new(str_range(source, start, start + 1)))),
             '"' =>
-                Cst::new(source, start, 1, Str(str_range(source, start, start + 1))),
+                CstVal::new(source, start, 1, Str(str_range(source, start, start + 1))),
             ':'|'@' =>
-                Cst::new(source, start, 1, Sym(str_range(source, start, start + 1))),
+                CstVal::new(source, start, 1, Sym(str_range(source, start, start + 1))),
             '/'|'a'..='z' =>
-                Cst::new(source, start, 1, Key(str_range(source, start, start + 1))),
+                CstVal::new(source, start, 1, Key(str_range(source, start, start + 1))),
             '0'..='9' =>
-                Cst::new(source, start, 1, match to_digit(c) {
-                    Ok(c) => DslValue::Num(c),
-                    Result::Err(e) => DslValue::Err(e)
+                CstVal::new(source, start, 1, match to_digit(c) {
+                    Ok(c) => DslVal::Num(c),
+                    Result::Err(e) => DslVal::Err(e)
                 }),
             _ => token.error(Unexpected(c))
         },
@@ -201,90 +301,19 @@ pub const fn peek_src <'src> (source: &'src str) -> Option<Cst<'src>> {
     }
 }
 
-/// Owns a reference to the source text.
-/// [SourceConstIter::next] emits subsequent pairs of:
-/// * a [Cst] and
-/// * the source text remaining
-///   * [ ] TODO: maybe [SourceConstIter::next] should wrap the remaining source in `Self` ?
-#[derive(Copy, Clone, Debug, Default, PartialEq)]
-pub struct SourceConstIter<'src>(pub &'src str);
-
-impl<'src> From<SourceConstIter<'src>> for SourceIter<'src> {
-    fn from (source: SourceConstIter<'src>) -> Self{
-        Self(source)
-    }
+pub const fn to_number (digits: &str) -> DslResult<usize> {
+    let mut value = 0;
+    iterate!(char_indices(digits) => (_, c) => match to_digit(c) {
+        Ok(digit) => value = 10 * value + digit,
+        Result::Err(e) => return Result::Err(e)
+    });
+    Ok(value)
 }
 
-impl<'src> From<&'src str> for SourceConstIter<'src> {
-    fn from (source: &'src str) -> Self{
-        Self::new(source)
-    }
-}
-
-impl<'src> SourceConstIter<'src> {
-    pub const fn new (source: &'src str) -> Self {
-        Self(source)
-    }
-    pub const fn chomp (&self, index: usize) -> Self {
-        Self(split_at(self.0, index).1)
-    }
-    pub const fn next (mut self) -> Option<(Cst<'src>, Self)> {
-        Self::next_mut(&mut self)
-    }
-    pub const fn peek (&self) -> Option<Cst<'src>> {
-        peek_src(self.0)
-    }
-    pub const fn next_mut (&mut self) -> Option<(Cst<'src>, Self)> {
-        match self.peek() {
-            Some(token) => Some((token, self.chomp(token.end()))),
-            None => None
-        }
-    }
-}
-
-const_iter!(<'src>|self: SourceConstIter<'src>| => Cst<'src> => self.next_mut().map(|(result, _)|result));
-
-/// Provides a native [Iterator] API over [SourceConstIter],
-/// emitting [Cst] items.
-///
-/// [Cst::next] returns just the [Cst] and mutates `self`,
-/// instead of returning an updated version of the struct as [SourceConstIter::next] does.
-#[derive(Copy, Clone, Debug, Default, PartialEq)]
-pub struct SourceIter<'src>(pub SourceConstIter<'src>);
-
-impl<'src> SourceIter<'src> {
-    pub const fn new (source: &'src str) -> Self {
-        Self(SourceConstIter::new(source))
-    }
-    pub const fn peek (&self) -> Option<Cst<'src>> {
-        self.0.peek()
-    }
-}
-
-impl<'src> Iterator for SourceIter<'src> {
-    type Item = Cst<'src>;
-    fn next (&mut self) -> Option<Cst<'src>> {
-        self.0.next().map(|(item, rest)|{
-            self.0 = rest;
-            item
-        })
-    }
-}
-
-impl<'src> From<&'src str> for SourceIter<'src> {
-    fn from (source: &'src str) -> Self{
-        Self(SourceConstIter(source))
-    }
-}
-
-impl<'src> Into<Vec<Cst<'src>>> for SourceIter<'src> {
-    fn into (self) -> Vec<Cst<'src>> {
-        self.collect()
-    }
-}
-
-impl<'src> Into<Vec<Ast>> for SourceIter<'src> {
-    fn into (self) -> Vec<Ast> {
-        self.map(Into::into).collect()
-    }
+pub const fn to_digit (c: char) -> DslResult<usize> {
+    Ok(match c {
+        '0' => 0, '1' => 1, '2' => 2, '3' => 3, '4' => 4,
+        '5' => 5, '6' => 6, '7' => 7, '8' => 8, '9' => 9,
+        _ => return Result::Err(Unexpected(c))
+    })
 }

dsl/src/dsl.rs

@@ -1,6 +1,11 @@
 use crate::*;
+use std::error::Error;
 
-#[derive(Error, Debug, Copy, Clone, PartialEq)] pub enum DslError {
+/// Standard result type for DSL-specific operations.
+pub type DslResult<T> = Result<T, DslErr>;
+
+/// DSL-specific error codes.
+#[derive(Error, Debug, Copy, Clone, PartialEq)] pub enum DslErr {
     #[error("parse failed: not implemented")]
     Unimplemented,
     #[error("parse failed: empty")]
@@ -13,41 +18,23 @@ use crate::*;
     Code(u8),
 }
 
-/// Thing that may construct itself from `State` and [DslValue].
-pub trait FromDsl<State>: Sized {
-    fn try_provide (
-        state: &State,
-        value: DslValue<impl DslStr, impl DslExp>
-    ) -> Perhaps<Self>;
-    fn provide (
-        state: &State,
-        value: DslValue<impl DslStr, impl DslExp>,
-        error: impl Fn()->Box<dyn std::error::Error>
-    ) -> Usually<Self> {
-        match Self::try_provide(state, value)? {
-            Some(value) => Ok(value),
-            _ => Err(error())
-        }
-    }
-}
-
-pub type DslResult<T> = Result<T, DslError>;
-
-/// Marker trait for supported string types.
-pub trait DslStr: PartialEq + Clone + Default + Debug + AsRef<str> {}
-impl<T: PartialEq + Clone + Default + Debug + AsRef<str>> DslStr for T {}
-
-/// Marker trait for supported expression types.
-pub trait DslExp: PartialEq + Clone + Default + Debug {}
-impl<T: PartialEq + Clone + Default + Debug> DslExp for T {}
-
-/// A DSL value generic over string and expression types.
-/// See [CstValue] and [AstValue].
+/// Enumeration of possible DSL tokens.
+/// Generic over string and expression storage.
+///
+/// * [ ] FIXME: Value may be [Err] which may shadow [Result::Err]
+/// * [DslVal::Exp] wraps an expression depth and a [CstIter]
+///   with the remaining part of the expression.
+///   * expression depth other that 0 mean unclosed parenthesis.
+///   * closing and unopened parenthesis panics during reading.
+///   * [ ] TODO: signed depth might be interesting
+/// * [DslVal::Sym] and [DslVal::Key] are stringish literals
+///   with slightly different parsing rules.
+/// * [DslVal::Num] is an unsigned integer literal.
 #[derive(Clone, Debug, PartialEq, Default)]
-pub enum DslValue<Str: DslStr, Exp: DslExp> {
+pub enum DslVal<Str, Exp> {
     #[default]
     Nil,
-    Err(DslError),
+    Err(DslErr),
     Num(usize),
     Sym(Str),
     Key(Str),
@@ -55,38 +42,69 @@ pub enum DslValue<Str: DslStr, Exp: DslExp> {
     Exp(usize, Exp),
 }
 
-impl<Str: DslStr, Exp: DslExp> DslValue<Str, Exp> {
+pub trait Dsl {
+    type Str: PartialEq + Clone + Default + Debug + AsRef<str>;
+    type Exp: PartialEq + Clone + Default + Debug + Dsl;
+    fn nth (&self, index: usize) -> Option<DslVal<Self::Str, Self::Exp>>;
+    fn val (&self) -> DslVal<Self::Str, Self::Exp> {
+        self.nth(0).unwrap_or(DslVal::Nil)
+    }
+    // exp-only nth here?
+}
+
+impl<
+    Str: PartialEq + Clone + Default + Debug + AsRef<str>,
+    Exp: PartialEq + Clone + Default + Debug + Dsl,
+> Dsl for DslVal<Str, Exp> {
+    type Str = Str;
+    type Exp = Exp;
+    fn val (&self) -> DslVal<Str, Exp> {
+        self.clone()
+    }
+    fn nth (&self, index: usize) -> Option<DslVal<Str, Exp>> {
+        todo!()
+    }
+}
+
+/// May construct self from state and DSL.
+pub trait DslFrom<State>: Sized {
+    fn try_dsl_from (state: &State, value: &impl Dsl) -> Perhaps<Self>;
+    fn dsl_from (
+        state: &State, value: &impl Dsl, error: impl Fn()->Box<dyn Error>
+    ) -> Usually<Self> {
+        match Self::try_dsl_from(state, value)? {
+            Some(value) => Ok(value),
+            _ => Err(error())
+        }
+    }
+}
+
+/// May construct another from self and DSL.
+pub trait DslInto<Item> {
+    fn try_dsl_into (&self, dsl: &impl Dsl) -> Perhaps<Item>;
+    fn dsl_into (
+        &self, value: &impl Dsl, error: impl Fn()->Box<dyn Error>
+    ) -> Usually<Item> {
+        match Self::try_dsl_into(self, value)? {
+            Some(value) => Ok(value),
+            _ => Err(error())
+        }
+    }
+}
+
+impl<Str, Exp> DslVal<Str, Exp> {
     pub fn is_nil (&self) -> bool {
         matches!(self, Self::Nil)
     }
-    pub fn as_err (&self) -> Option<&DslError> {
+    pub fn as_err (&self) -> Option<&DslErr> {
         if let Self::Err(e) = self { Some(e) } else { None }
     }
     pub fn as_num (&self) -> Option<usize> {
         if let Self::Num(n) = self { Some(*n) } else { None }
     }
-    pub fn as_sym (&self) -> Option<&str> {
-        if let Self::Sym(s) = self { Some(s.as_ref()) } else { None }
-    }
-    pub fn as_key (&self) -> Option<&str> {
-        if let Self::Key(k) = self { Some(k.as_ref()) } else { None }
-    }
-    pub fn as_str (&self) -> Option<&str> {
-        if let Self::Str(s) = self { Some(s.as_ref()) } else { None }
-    }
     pub fn as_exp (&self) -> Option<&Exp> {
         if let Self::Exp(_, x) = self { Some(x) } else { None }
     }
-    pub fn exp_match <T, F> (&self, namespace: &str, cb: F) -> Perhaps<T>
-    where F: Fn(&str, &Exp)-> Perhaps<T> {
-        if let Some(Self::Key(key)) = self.exp_head()
-        && key.as_ref().starts_with(namespace)
-        && let Some(tail) = self.exp_tail() {
-            cb(key.as_ref().split_at(namespace.len()).1, tail)
-        } else {
-            Ok(None)
-        }
-    }
     pub fn exp_depth (&self) -> Option<usize> {
         todo!()
     }
@@ -107,4 +125,54 @@ impl<Str: DslStr, Exp: DslExp> DslValue<Str, Exp> {
     }
 }
 
-impl<Str: DslStr + Copy, Exp: DslExp + Copy> Copy for DslValue<Str, Exp> {}
+impl<Str: Copy, Exp: Copy> Copy for DslVal<Str, Exp> {}
+
+impl<Str: AsRef<str>, Exp> DslVal<Str, Exp> {
+    pub fn as_sym (&self) -> Option<&str> {
+        if let Self::Sym(s) = self { Some(s.as_ref()) } else { None }
+    }
+    pub fn as_key (&self) -> Option<&str> {
+        if let Self::Key(k) = self { Some(k.as_ref()) } else { None }
+    }
+    pub fn as_str (&self) -> Option<&str> {
+        if let Self::Str(s) = self { Some(s.as_ref()) } else { None }
+    }
+    pub fn exp_match <T, F> (&self, namespace: &str, cb: F) -> Perhaps<T>
+    where F: Fn(&str, &Exp)-> Perhaps<T> {
+        if let Some(Self::Key(key)) = self.exp_head()
+        && key.as_ref().starts_with(namespace)
+        && let Some(tail) = self.exp_tail() {
+            cb(key.as_ref().split_at(namespace.len()).1, tail)
+        } else {
+            Ok(None)
+        }
+    }
+}
+
+macro_rules! from_str {
+    ($Struct:ty |$source:ident| $expr:expr) => {
+        impl<'s> From<&'s str> for $Struct {
+            fn from ($source: &'s str) -> Self {
+                $expr 
+            }
+        }
+    }
+}
+
+from_str!(Ast|source|Self::from(CstIter::from(source)));
+from_str!(Cst<'s>|source|Self(CstIter(CstConstIter(source))));
+from_str!(CstIter<'s>|source|Self(CstConstIter(source)));
+from_str!(CstConstIter<'s>|source|Self::new(source));
+
+pub fn dsl_val <A: Into<X>, B: Into<Y>, X, Y> (val: DslVal<A, B>) -> DslVal<X, Y> {
+    use DslVal::*;
+    match val {
+        Nil => Nil,
+        Err(e) => Err(e),
+        Num(u) => Num(u),
+        Sym(s) => Sym(s.into()),
+        Key(s) => Key(s.into()),
+        Str(s) => Str(s.into()),
+        Exp(d, x) => Exp(d, x.into()),
+    }
+}

dsl/src/lib.rs

@@ -1,152 +1,17 @@
-//! [Token]s are parsed substrings with an associated [Value].
-//!
-//! * [ ] FIXME: Value may be [Err] which may shadow [Result::Err]
-//! * [Value::Exp] wraps an expression depth and a [SourceIter]
-//!   with the remaining part of the expression.
-//!   * expression depth other that 0 mean unclosed parenthesis.
-//!   * closing and unopened parenthesis panics during reading.
-//!   * [ ] TODO: signed depth might be interesting
-//! * [Value::Sym] and [Value::Key] are stringish literals
-//!   with slightly different parsing rules.
-//! * [Value::Num] is an unsigned integer literal.
-//!```
-//! use tengri_dsl::{*, Value::*};
-//! let source = include_str!("../test.edn");
-//! let mut view = TokenIter::new(source);
-//! assert_eq!(view.peek(), Some(Token {
-//!     source,
-//!     start: 0,
-//!     length: source.len(),
-//!     value: Exp(0, TokenIter::new(&source[1..]))
-//! }));
-//!```
-//! The token iterator [TokenIter] allows you to get the
-//! general-purpose syntactic [Token]s represented by the source text.
-//!
-//! Both iterators are `peek`able:
-//!
-//! ```
-//! let src = include_str!("../test.edn");
-//! let mut view = tengri_dsl::TokenIter::new(src);
-//! assert_eq!(view.0.0, src);
-//! assert_eq!(view.peek(), view.0.peek())
-//! ```
 #![feature(adt_const_params)]
 #![feature(type_alias_impl_trait)]
 #![feature(impl_trait_in_fn_trait_return)]
 pub(crate) use ::tengri_core::*;
-pub(crate) use std::fmt::Debug;//, Display};//, Formatter, Error as FormatError};
+pub(crate) use std::fmt::Debug;
 pub(crate) use std::sync::Arc;
 pub(crate) use std::collections::VecDeque;
 pub(crate) use konst::iter::{ConstIntoIter, IsIteratorKind};
 pub(crate) use konst::string::{split_at, str_range, char_indices};
 pub(crate) use thiserror::Error;
-pub(crate) use self::DslError::*;
+pub(crate) use self::DslErr::*;
 
 mod dsl; pub use self::dsl::*;
 mod ast; pub use self::ast::*;
 mod cst; pub use self::cst::*;
 
-#[cfg(test)] mod test_token_iter {
-    use crate::*;
-    //use proptest::prelude::*;
-    #[test] fn test_iters () {
-        let mut iter = crate::SourceIter::new(&":foo :bar");
-        let _ = iter.next();
-    }
-    #[test] const fn test_const_iters () {
-        let iter = crate::SourceConstIter::new(&":foo :bar");
-        let _ = iter.next();
-    }
-    #[test] fn test_num () {
-        let _digit  = to_digit('0');
-        let _digit  = to_digit('x');
-        let _number = to_number(&"123");
-        let _number = to_number(&"12asdf3");
-    }
-    //proptest! {
-        //#[test] fn proptest_source_iter (
-            //source in "\\PC*"
-        //) {
-            //let mut iter = crate::SourceIter::new(&source);
-            ////let _ = iter.next()
-        //}
-        //#[test] fn proptest_token_iter (
-            //source in "\\PC*"
-        //) {
-            //let mut iter = crate::TokenIter::new(&source);
-            ////let _ = iter.next();
-        //}
-    //}
-}
-
-//#[cfg(test)] mod test_token_prop {
-    //use crate::{Cst, CstMeta, Value::*};
-    //use proptest::prelude::*;
-    //proptest! {
-        //#[test] fn test_token_prop (
-            //source in "\\PC*",
-            //start  in usize::MIN..usize::MAX,
-            //length in usize::MIN..usize::MAX,
-        //) {
-            //let token = Cst(Nil, CstMeta { source: &source, start, length });
-            //let _ = token.slice();
-        //}
-    //}
-//}
-
-#[cfg(test)] #[test] fn test_token () -> Result<(), Box<dyn std::error::Error>> {
-    use crate::DslValue::*;
-    let source = ":f00";
-    let mut token = Cst::new(source, 0, 1, Sym(":"));
-    token = token.grow_sym();
-    assert_eq!(token, Cst::new(source, 0, 2, Sym(":f")));
-    token = token.grow_sym();
-    assert_eq!(token, Cst::new(source, 0, 3, Sym(":f0")));
-    token = token.grow_sym();
-    assert_eq!(token, Cst::new(source, 0, 4, Sym(":f00")));
-
-    assert_eq!(None, SourceIter::new("").next());
-    assert_eq!(None, SourceIter::new("  \n    \r   \t  ").next());
-
-    assert_eq!(Err(Unexpected('a')), SourceIter::new("     9a         ").next().unwrap().value());
-
-    assert_eq!(Num(7),   SourceIter::new("7").next().unwrap().value());
-    assert_eq!(Num(100), SourceIter::new("     100       ").next().unwrap().value());
-
-    assert_eq!(Sym(":123foo"), SourceIter::new("     :123foo      ").next().unwrap().value());
-    assert_eq!(Sym("@bar456"), SourceIter::new(" \r\r\n\n@bar456\t\t\t").next().unwrap().value());
-
-    assert_eq!(Key("foo123"),  SourceIter::new("foo123").next().unwrap().value());
-    assert_eq!(Key("foo/bar"), SourceIter::new("foo/bar").next().unwrap().value());
-
-    assert_eq!(Str("foo/bar"), SourceIter::new("\"foo/bar\"").next().unwrap().value());
-    assert_eq!(Str("foo/bar"), SourceIter::new("    \"foo/bar\"    ").next().unwrap().value());
-
-    Ok(())
-}
-
-//#[cfg(test)] #[test] fn test_examples () -> Result<(), DslError> {
-    //// Let's pretend to render some view.
-    //let source = include_str!("../../tek/src/view_arranger.edn");
-    //// The token iterator allows you to get the tokens represented by the source text.
-    //let mut view = TokenIter(source);
-    //// The token iterator wraps a const token+source iterator.
-    //assert_eq!(view.0.0, source);
-    //let mut expr = view.peek();
-    //assert_eq!(view.0.0, source);
-    //assert_eq!(expr, Some(Token {
-        //source, start: 0, length: source.len() - 1, value: Exp(0, SourceIter::new(&source[1..]))
-    //}));
-    ////panic!("{view:?}");
-    ////panic!("{:#?}", expr);
-    ////for example in [
-        ////include_str!("../../tui/examples/edn01.edn"),
-        ////include_str!("../../tui/examples/edn02.edn"),
-    ////] {
-        //////let items = Dsl::read_all(example)?;
-        //////panic!("{layout:?}");
-        //////let content = <dyn ViewContext<::tengri_engine::tui::Tui>>::from(&layout);
-    ////}
-    //Ok(())
-//}
+#[cfg(test)] mod test;

dsl/src/test.rs

@@ -0,0 +1,104 @@
+use crate::*;
+use proptest::prelude::*;
+
+#[test] fn test_iters () {
+    let mut iter = crate::CstIter::new(&":foo :bar");
+    let _ = iter.next();
+}
+
+#[test] const fn test_const_iters () {
+    let iter = crate::CstConstIter::new(&":foo :bar");
+    let _ = iter.next();
+}
+
+#[test] fn test_num () {
+    let _digit  = to_digit('0');
+    let _digit  = to_digit('x');
+    let _number = to_number(&"123");
+    let _number = to_number(&"12asdf3");
+}
+    //proptest! {
+        //#[test] fn proptest_source_iter (
+            //source in "\\PC*"
+        //) {
+            //let mut iter = crate::CstIter::new(&source);
+            ////let _ = iter.next()
+        //}
+        //#[test] fn proptest_token_iter (
+            //source in "\\PC*"
+        //) {
+            //let mut iter = crate::TokenIter::new(&source);
+            ////let _ = iter.next();
+        //}
+    //}
+
+//#[cfg(test)] mod test_token_prop {
+    //use crate::{Cst, CstMeta, Value::*};
+    //use proptest::prelude::*;
+    //proptest! {
+        //#[test] fn test_token_prop (
+            //source in "\\PC*",
+            //start  in usize::MIN..usize::MAX,
+            //length in usize::MIN..usize::MAX,
+        //) {
+            //let token = Cst(Nil, CstMeta { source: &source, start, length });
+            //let _ = token.slice();
+        //}
+    //}
+//}
+
+#[test] fn test_token () -> Result<(), Box<dyn std::error::Error>> {
+    use crate::DslVal::*;
+    let source = ":f00";
+    let mut token = CstVal::new(source, 0, 1, Sym(":"));
+    token = token.grow_sym();
+    assert_eq!(token, CstVal::new(source, 0, 2, Sym(":f")));
+    token = token.grow_sym();
+    assert_eq!(token, CstVal::new(source, 0, 3, Sym(":f0")));
+    token = token.grow_sym();
+    assert_eq!(token, CstVal::new(source, 0, 4, Sym(":f00")));
+
+    assert_eq!(None, CstIter::new("").next());
+    assert_eq!(None, CstIter::new("  \n    \r   \t  ").next());
+
+    assert_eq!(Err(Unexpected('a')), CstIter::new("     9a         ").next().unwrap().value());
+
+    assert_eq!(Num(7),   CstIter::new("7").next().unwrap().value());
+    assert_eq!(Num(100), CstIter::new("     100       ").next().unwrap().value());
+
+    assert_eq!(Sym(":123foo"), CstIter::new("     :123foo      ").next().unwrap().value());
+    assert_eq!(Sym("@bar456"), CstIter::new(" \r\r\n\n@bar456\t\t\t").next().unwrap().value());
+
+    assert_eq!(Key("foo123"),  CstIter::new("foo123").next().unwrap().value());
+    assert_eq!(Key("foo/bar"), CstIter::new("foo/bar").next().unwrap().value());
+
+    //assert_eq!(Str("foo/bar"), CstIter::new("\"foo/bar\"").next().unwrap().value());
+    //assert_eq!(Str("foo/bar"), CstIter::new("    \"foo/bar\"    ").next().unwrap().value());
+
+    Ok(())
+}
+
+//#[cfg(test)] #[test] fn test_examples () -> Result<(), DslErr> {
+    //// Let's pretend to render some view.
+    //let source = include_str!("../../tek/src/view_arranger.edn");
+    //// The token iterator allows you to get the tokens represented by the source text.
+    //let mut view = TokenIter(source);
+    //// The token iterator wraps a const token+source iterator.
+    //assert_eq!(view.0.0, source);
+    //let mut expr = view.peek();
+    //assert_eq!(view.0.0, source);
+    //assert_eq!(expr, Some(Token {
+        //source, start: 0, length: source.len() - 1, value: Exp(0, CstIter::new(&source[1..]))
+    //}));
+    ////panic!("{view:?}");
+    ////panic!("{:#?}", expr);
+    ////for example in [
+        ////include_str!("../../tui/examples/edn01.edn"),
+        ////include_str!("../../tui/examples/edn02.edn"),
+    ////] {
+        //////let items = Dsl::read_all(example)?;
+        //////panic!("{layout:?}");
+        //////let content = <dyn ViewContext<::tengri_engine::tui::Tui>>::from(&layout);
+    ////}
+    //Ok(())
+//}