dsl: refactor with eyes closed

dsl/src/dsl.rs

@@ -16,9 +16,17 @@ pub(crate) use ::{
 };
 pub(crate) use self::DslError::*;
 mod dsl_conv; pub use self::dsl_conv::*;
-mod dsl_ns;   pub use self::dsl_ns::*;
-mod dsl_src;  pub use self::dsl_src::*;
 #[cfg(test)] mod dsl_test;
+// Trait that designates any string-like as potentially parsable DSL.
+flex_trait!(Dsl: AsRef<str> + Debug + Send + Sync + Sized {
+    fn src (&self) -> DslPerhaps<&str> {Ok(Some(self.as_ref()))}
+});
+impl<D: Dsl> Dsl for Option<D> {
+    fn src (&self) -> DslPerhaps<&str> {Ok(if let Some(dsl) = self { dsl.src()? } else { None })}
+}
+impl<D: Dsl> Dsl for Result<D, DslError> {
+    fn src (&self) -> DslPerhaps<&str> {match self {Ok(dsl) => Ok(dsl.src()?), Err(e) => Err(*e)}}
+}
 /// DSL-specific result type.
 pub type DslResult<T> = Result<T, DslError>;
 /// DSL-specific optional result type.
@@ -39,23 +47,6 @@ pub enum DslError {
     #[error("end reached")]
     End
 }
-fn ok_flat <T> (x: Option<DslPerhaps<T>>) -> DslPerhaps<T> {
-    Ok(x.transpose()?.flatten())
-}
-pub const fn is_space (c: char) -> bool {
-    matches!(c, ' '|'\n'|'\r'|'\t')
-}
-pub const fn no_trailing_non_space (
-    src: &str, offset: usize, context: Option<&'static str>
-) -> DslResult<()> {
-    Ok(for_each!((i, c) in char_indices(str_range(src, offset, src.len())) => if !is_space(c) {
-        return Err(Unexpected(c, Some(offset + i), if let Some(context) = context {
-            Some(context)
-        } else {
-            Some("trailing non-space")
-        }))
-    }))
-}
 pub const fn peek (src: &str) -> DslPerhaps<&str> {
     Ok(Some(if let Ok(Some(expr)) = expr_peek(src) { expr } else
             if let Ok(Some(word)) = word_peek(src) { word } else
@@ -83,7 +74,74 @@ pub const fn peek_tail (src: &str) -> DslPerhaps<&str> {
         },
     }
 }
-
+pub const fn expr_peek_inner (src: &str) -> DslPerhaps<&str> {
+    match expr_peek(src) {
+        Ok(Some(peeked)) => {
+            let len = peeked.len();
+            let start = if len > 0 { 1 } else { 0 };
+            Ok(Some(str_range(src, start, start + len.saturating_sub(2))))
+        },
+        e => e
+    }
+}
+pub const fn expr_peek_inner_only (src: &str) -> DslPerhaps<&str> {
+    match expr_seek(src) {
+        Err(e) => Err(e),
+        Ok(None) => Ok(None),
+        Ok(Some((start, length))) => {
+            if let Err(e) = no_trailing_non_space(src, start + length, Some("expr_peek_inner_only")) {
+                Err(e)
+            } else {
+                let peeked = str_range(src, start, start + length);
+                let len = peeked.len();
+                let start = if len > 0 { 1 } else { 0 };
+                Ok(Some(str_range(peeked, start, start + len.saturating_sub(2))))
+            }
+        },
+    }
+}
+pub const fn is_space (c: char) -> bool {
+    matches!(c, ' '|'\n'|'\r'|'\t')
+}
+pub const fn no_trailing_non_space (
+    src: &str, offset: usize, context: Option<&'static str>
+) -> DslResult<()> {
+    Ok(for_each!((i, c) in char_indices(str_range(src, offset, src.len())) => if !is_space(c) {
+        return Err(Unexpected(c, Some(offset + i), if let Some(context) = context {
+            Some(context)
+        } else {
+            Some("trailing non-space")
+        }))
+    }))
+}
+pub const fn is_word_char (c: char) -> bool {
+    matches!(c, 'a'..='z'|'A'..='Z'|'0'..='9'|'-'|'/'|'@'|':')
+}
+pub const fn is_word_end (c: char) -> bool { is_space(c) || is_expr_end(c) }
+pub const fn is_text_start (c: char) -> bool { matches!(c, '"') }
+pub const fn is_text_end (c: char) -> bool { matches!(c, '"') }
+pub const fn is_expr_start (c: char) -> bool { c == '(' }
+pub const fn is_expr_end (c: char) -> bool { c == ')' }
+pub const fn is_digit (c: char) -> bool { matches!(c, '0'..='9') }
+pub const fn to_number (digits: &str) -> Result<usize, DslError> {
+    let mut iter = char_indices(digits);
+    let mut value = 0;
+    while let Some(((_, c), next)) = iter.next() {
+        match to_digit(c) {
+            Ok(digit) => value = 10 * value + digit,
+            Err(e) => return Err(e),
+        }
+        iter = next;
+    }
+    Ok(value)
+}
+pub const fn to_digit (c: char) -> Result<usize, DslError> {
+    Ok(match c {
+        '0' => 0, '1' => 1, '2' => 2, '3' => 3, '4' => 4,
+        '5' => 5, '6' => 6, '7' => 7, '8' => 8, '9' => 9,
+        _ => return Err(Unexpected(c, None, Some("parse digit")))
+    })
+}
 #[macro_export] macro_rules! dsl_type (($T:ident { $($trait:tt)* } {
     pub const fn $peek:ident      $($_1:tt)?;
     pub const fn $peek_only:ident $($_2:tt)?;
@@ -93,6 +151,20 @@ pub const fn peek_tail (src: &str) -> DslPerhaps<&str> {
 })=>{
     pub trait $T: Dsl { $($trait)* }
     impl<D: Dsl> $T for D {}
+    pub const fn $seek_start  ($source1: &str) -> DslPerhaps<usize> $body1
+    pub const fn $seek_length ($source2: &str) -> DslPerhaps<usize> $body2
+    /// Find a start and length corresponding to a syntax token.
+    pub const fn $seek (source: &str) -> DslPerhaps<(usize, usize)> {
+        match $seek_start(source) {
+            Err(e) => Err(e),
+            Ok(None) => Ok(None),
+            Ok(Some(start)) => match $seek_length(str_from(source, start)) {
+                Ok(Some(length)) => Ok(Some((start, length))),
+                Ok(None) => Ok(None),
+                Err(e) => Err(e),
+            },
+        }
+    }
     /// Find a slice corrensponding to a syntax token.
     pub const fn $peek (source: &str) -> DslPerhaps<&str> {
         match $seek(source) {
@@ -109,29 +181,53 @@ pub const fn peek_tail (src: &str) -> DslPerhaps<&str> {
             Err(e) => Err(e),
             Ok(None) => Ok(None),
             Ok(Some((start, length))) => {
-                if let Err(e) = no_trailing_non_space(source, start + length, Some("peek_only")) { return Err(e) }
+                if let Err(e) = no_trailing_non_space(source, start + length, Some("peek_only")) {
+                    Err(e)
+                } else {
                     Ok(Some(str_range(source, start, start + length)))
                 }
             }
         }
-    /// Find a start and length corresponding to a syntax token.
-    pub const fn $seek (source: &str) -> DslPerhaps<(usize, usize)> {
-        match $seek_start(source) {
-            Err(e) => Err(e),
-            Ok(None) => Ok(None),
-            Ok(Some(start)) => match $seek_length(str_from(source, start)) {
-                Ok(Some(length)) => Ok(Some((start, length))),
-                Ok(None) => Ok(None),
-                Err(e) => Err(e),
-            },
     }
-    }
-    pub const fn $seek_start  ($source1: &str) -> DslPerhaps<usize> $body1
-    pub const fn $seek_length ($source2: &str) -> DslPerhaps<usize> $body2
 });
 
-pub const fn is_expr_start (c: char) -> bool { c == '(' }
-pub const fn is_expr_end (c: char) -> bool { c == ')' }
+dsl_type!(DslWord {
+    fn word (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(word_peek_only))}
+} {
+    pub const fn word_peek      [generated];
+    pub const fn word_peek_only [generated];
+    pub const fn word_seek      [generated];
+    pub const fn word_seek_start (src) {
+        for_each!((i, c) in char_indices(src) => if
+            is_word_char(c)  { return Ok(Some(i)) } else
+            if !is_space(c) { return Err(Unexpected(c, Some(i), Some("word_seek_start"))) });
+        Ok(None)
+    }
+    pub const fn word_seek_length (src) {
+        for_each!((i, c) in char_indices(src) => if !is_word_char(c) { return Ok(Some(i)) });
+        Ok(Some(src.len()))
+    }
+});
+
+dsl_type!(DslText {
+    fn text (&self) -> DslPerhaps<&str> { ok_flat(self.src()?.map(text_peek_only)) }
+} {
+    pub const fn text_peek      [generated];
+    pub const fn text_peek_only [generated];
+    pub const fn text_seek      [generated];
+    pub const fn text_seek_start (src) {
+        for_each!((i, c) in char_indices(src) =>
+            if is_text_start(c) { return Ok(Some(i)) } else
+            if !is_space(c)     { return Err(Unexpected(c, Some(i), None)) });
+        Ok(None)
+    }
+    pub const fn text_seek_length (src) {
+        for_each!((i, c) in char_indices(src) =>
+            if is_text_end(c) { return Ok(Some(i)) });
+        Ok(None)
+    }
+});
+
 dsl_type!(DslExpr {
     fn expr  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(expr_peek_inner_only))}
     fn head (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(peek))}
@@ -172,113 +268,129 @@ dsl_type!(DslExpr {
     }
 });
 
-pub const fn expr_peek_inner (src: &str) -> DslPerhaps<&str> {
-    match expr_peek(src) {
-        Ok(Some(peeked)) => {
-            let len = peeked.len();
-            let start = if len > 0 { 1 } else { 0 };
-            Ok(Some(str_range(src, start, start + len.saturating_sub(2))))
-        },
-        e => e
+fn ok_flat <T> (x: Option<DslPerhaps<T>>) -> DslPerhaps<T> {
+    Ok(x.transpose()?.flatten())
+}
+
+/// Define a DSL namespace that provides values to words and expressions.
+#[macro_export] macro_rules! dsl_ns (
+    // Special form for numeric types
+    (num |$state:ident : $State: ty| $($($num:lifetime)? $Type:ty $(=> { $(
+        $pat:tt => $body:expr
+    ),* $(,)? })?;)+) => {
+        $(dsl_ns!(num |$state: $State| -> $($num)? $Type { $( $($pat => $body),* )? });)+
+    };
+    // Special form for numeric types
+    (num |$state:ident : $State: ty| -> $Type:ty { $( $pat:tt => $body:expr ),* $(,)? }) => {
+        impl<'t> DslNs<'t, $Type> for $State {
+            const WORDS: DslNsMap<'t, fn (&'t $State)->Perhaps<$Type>> =
+                DslNsMap::new(&[$(dsl_ns!{@word ($state: $State) -> $Type { $pat => $body }}),*]);
+            const EXPRS: DslNsMap<'t, fn (&'t $State, &str)->Perhaps<$Type>> =
+                DslNsMap::new(&[$(dsl_ns!{@exp ($state: $State) -> $Type { $pat => $body }}),*]);
+            fn from <D: Dsl> (&'t self, dsl: D) -> Perhaps<$Type> {
+                if let Ok(Some(src)) = dsl.src() {
+                    if let Ok(num) = to_number(src) {
+                        Ok(Some(num as $Type))
+                    } else if let Ok(Some(src)) = src.word() {
+                        self.from_word(src)
+                    } else {
+                        self.from_expr(src)
+                    }
+                } else {
+                    Ok(None)
+                }
+            }
+        }
+    };
+    // A namespace may resolve one or more types.
+    (|$state:ident : $State: ty| $($Type:ty $(=> { $( $pat:tt => $body:expr ),* $(,)? })? ;)+) => {
+        $(dsl_ns!(|$state: $State| -> $Type { $( $($pat => $body),* )? });)+
+    };
+    // Regular form for single type
+    (|$state:ident : $State: ty| -> $Type:ty { $( $pat:tt => $body:expr ),* $(,)? }) => {
+        impl<'t> DslNs<'t, $Type> for $State {
+            const WORDS: DslNsMap<'t, fn (&'t $State)->Perhaps<$Type>> =
+                DslNsMap::new(&[$(dsl_ns!{@word ($state: $State) -> $Type { $pat => $body }}),*]);
+            const EXPRS: DslNsMap<'t, fn (&'t $State, &str)->Perhaps<$Type>> =
+                DslNsMap::new(&[$(dsl_ns!{@exp ($state: $State) -> $Type { $pat => $body }}),*]);
+        }
+    };
+    // Symbols only.
+    (@word ($state:ident: $State:ty) -> $Type:ty {
+        $word:literal => $body:expr
+    }) => {
+        ($word, |$state|Ok(Some($body)))
+    };
+    // Expression handlers only.
+    (@exp ($state:ident: $State:ty) -> $Type:ty {
+        ($head:literal $(,$arg:ident:$ty:ty)* $(,)*) => $body:expr
+    }) => { ($head, |$state, tail: &str|{
+        $(
+            let head = tail.head()?.unwrap_or_default();
+            let tail = tail.tail()?.unwrap_or_default();
+            let $arg: $ty = if let Some(arg) = $state.from(&head)? {
+                arg
+            } else {
+                return Err(format!("{}: missing argument: {} ({}); got: {tail}",
+                    $head,
+                    stringify!($arg),
+                    stringify!($Type),
+                ).into())
+            };
+        )*
+        Ok(Some($body))
+    }) };
+    // Nothing else in symbols.
+    (@word ($state:ident: $State:ty) -> $Type:ty { $pat:tt => $body:expr }) => {
+        ("", |_|Ok(None)) // FIXME don't emit at all
+    };
+    // Nothing else in expression handlers.
+    (@exp ($state:ident: $State:ty) -> $Type:ty { $pat:tt => $body:expr }) => {
+        ("", |_, _|Ok(None)) // FIXME don't emit at all
+    };
+);
+
+pub trait DslNs<'t, T: 't>: 't {
+    /// Known symbols.
+    const WORDS: DslNsMap<'t, fn (&'t Self)->Perhaps<T>> = DslNsMap::new(&[]);
+    /// Known expressions.
+    const EXPRS: DslNsMap<'t, fn (&'t Self, &str)->Perhaps<T>> = DslNsMap::new(&[]);
+    /// Resolve an expression or symbol.
+    fn from <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
+        if let Ok(Some(src)) = dsl.src() {
+            if let Ok(Some(src)) = src.word() {
+                self.from_word(src)
+            } else {
+                self.from_expr(src)
+            }
+        } else {
+            Ok(None)
+        }
+    }
+    /// Resolve a symbol if known.
+    fn from_word <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
+        if let Some(dsl) = dsl.word()? {
+            for (word, get) in Self::WORDS.0 { if dsl == *word { return get(self) } }
+        }
+        return Ok(None)
+    }
+    /// Resolve an expression if known.
+    fn from_expr <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
+        if let Some(head) = dsl.expr().head()? {
+            for (key, value) in Self::EXPRS.0.iter() {
+                if head == *key {
+                    return value(self, dsl.expr().tail()?.unwrap_or(""))
+                }
+            }
+        }
+        return Ok(None)
     }
 }
 
-pub const fn expr_peek_inner_only (src: &str) -> DslPerhaps<&str> {
-    match expr_seek(src) {
-        Err(e) => Err(e),
-        Ok(None) => Ok(None),
-        Ok(Some((start, length))) => {
-            if let Err(e) = no_trailing_non_space(src, start + length, Some("expr_peek_inner_only")) { return Err(e) }
-            let peeked = str_range(src, start, start + length);
-            let len = peeked.len();
-            let start = if len > 0 { 1 } else { 0 };
-            Ok(Some(str_range(peeked, start, start + len.saturating_sub(2))))
-        },
-    }
-}
-
-pub const fn is_word_char (c: char) -> bool {
-    matches!(c, 'a'..='z'|'A'..='Z'|'0'..='9'|'-'|'/'|'@'|':')
-}
-pub const fn is_word_end (c: char) -> bool {
-    is_space(c) || is_expr_end(c)
-}
-dsl_type!(DslWord {
-    fn word (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(word_peek_only))}
-} {
-    pub const fn word_peek      [generated];
-    pub const fn word_peek_only [generated];
-    pub const fn word_seek      [generated];
-    pub const fn word_seek_start (src) {
-        for_each!((i, c) in char_indices(src) => if
-            is_word_char(c)  { return Ok(Some(i)) } else
-            if !is_space(c) { return Err(Unexpected(c, Some(i), Some("word_seek_start"))) });
-        Ok(None)
-    }
-    pub const fn word_seek_length (src) {
-        for_each!((i, c) in char_indices(src) => if !is_word_char(c) { return Ok(Some(i)) });
-        Ok(Some(src.len()))
-    }
-});
-
-pub const fn is_text_start (c: char) -> bool { matches!(c, '"') }
-pub const fn is_text_end (c: char) -> bool { matches!(c, '"') }
-dsl_type!(DslText {
-    fn text (&self) -> DslPerhaps<&str> { ok_flat(self.src()?.map(text_peek_only)) }
-} {
-    pub const fn text_peek      [generated];
-    pub const fn text_peek_only [generated];
-    pub const fn text_seek      [generated];
-    pub const fn text_seek_start (src) {
-        for_each!((i, c) in char_indices(src) =>
-            if is_text_start(c) { return Ok(Some(i)) } else
-            if !is_space(c)     { return Err(Unexpected(c, Some(i), None)) });
-        Ok(None)
-    }
-    pub const fn text_seek_length (src) {
-        for_each!((i, c) in char_indices(src) =>
-            if is_text_end(c) { return Ok(Some(i)) });
-        Ok(None)
-    }
-});
-
-dsl_type!(DslNum {
-    fn num (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(num_peek_only))}
-} {
-    pub const fn num_peek      [generated];
-    pub const fn num_peek_only [generated];
-    pub const fn num_seek      [generated];
-    pub const fn num_seek_start (src) {
-        for_each!((i, c) in char_indices(src) =>
-            if is_digit(c)  { return Ok(Some(i)); } else
-            if !is_space(c) { return Err(Unexpected(c, Some(i), None)) });
-        Ok(None)
-    }
-    pub const fn num_seek_length (src) {
-        for_each!((i, c) in char_indices(src) =>
-            if is_num_end(c) { return Ok(Some(i)) } else
-            if !is_digit(c)  { return Err(Unexpected(c, Some(i), None)) });
-        Ok(None)
-    }
-});
-pub const fn is_digit (c: char) -> bool { matches!(c, '0'..='9') }
-pub const fn is_num_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
-pub const fn to_number (digits: &str) -> Result<usize, DslError> {
-    let mut iter = char_indices(digits);
-    let mut value = 0;
-    while let Some(((_, c), next)) = iter.next() {
-        match to_digit(c) {
-            Ok(digit) => value = 10 * value + digit,
-            Err(e) => return Err(e),
-        }
-        iter = next;
-    }
-    Ok(value)
-}
-pub const fn to_digit (c: char) -> Result<usize, DslError> {
-    Ok(match c {
-        '0' => 0, '1' => 1, '2' => 2, '3' => 3, '4' => 4,
-        '5' => 5, '6' => 6, '7' => 7, '8' => 8, '9' => 9,
-        _ => return Err(Unexpected(c, None, Some("parse digit")))
-    })
+/// Namespace mapping.
+#[derive(Debug)]
+pub struct DslNsMap<'t, T: Debug + 't>(pub &'t [(&'t str, T)]);
+impl<'t, T: Debug + 't> DslNsMap<'t, T> {
+    /// Populate a namespace with pre-existing values.
+    pub const fn new (data: &'t [(&'t str, T)]) -> Self { Self(data) /* TODO a search trie */ }
 }

dsl/src/dsl_ns.rs

@@ -1,125 +0,0 @@
-use crate::*;
-/// Define a namespace:
-#[macro_export] macro_rules! dsl_ns (
-    // Special form for numeric types
-    (num |$state:ident : $State: ty| $($($num:lifetime)? $Type:ty $(=> { $(
-        $pat:tt => $body:expr
-    ),* $(,)? })?;)+) => {
-        $(dsl_ns!(num |$state: $State| -> $($num)? $Type { $( $($pat => $body),* )? });)+
-    };
-    // Special form for numeric types
-    (num |$state:ident : $State: ty| -> $Type:ty { $( $pat:tt => $body:expr ),* $(,)? }) => {
-        impl<'t> DslNs<'t, $Type> for $State {
-            const WORDS: DslNsMap<'t, fn (&'t $State)->Perhaps<$Type>> =
-                DslNsMap::new(&[$(dsl_ns!{@word ($state: $State) -> $Type { $pat => $body }}),*]);
-            const EXPRS: DslNsMap<'t, fn (&'t $State, &str)->Perhaps<$Type>> =
-                DslNsMap::new(&[$(dsl_ns!{@exp ($state: $State) -> $Type { $pat => $body }}),*]);
-            fn from <D: Dsl> (&'t self, dsl: D) -> Perhaps<$Type> {
-                if let Ok(Some(src)) = dsl.src() {
-                    if let Ok(num) = to_number(src) {
-                        Ok(Some(num as $Type))
-                    } else if let Ok(Some(src)) = src.word() {
-                        self.from_word(src)
-                    } else {
-                        self.from_expr(src)
-                    }
-                } else {
-                    Ok(None)
-                }
-            }
-        }
-    };
-    // A namespace may resolve one or more types.
-    (|$state:ident : $State: ty| $($Type:ty $(=> { $( $pat:tt => $body:expr ),* $(,)? })? ;)+) => {
-        $(dsl_ns!(|$state: $State| -> $Type { $( $($pat => $body),* )? });)+
-    };
-    // Regular form for single type
-    (|$state:ident : $State: ty| -> $Type:ty { $( $pat:tt => $body:expr ),* $(,)? }) => {
-        impl<'t> DslNs<'t, $Type> for $State {
-            const WORDS: DslNsMap<'t, fn (&'t $State)->Perhaps<$Type>> =
-                DslNsMap::new(&[$(dsl_ns!{@word ($state: $State) -> $Type { $pat => $body }}),*]);
-            const EXPRS: DslNsMap<'t, fn (&'t $State, &str)->Perhaps<$Type>> =
-                DslNsMap::new(&[$(dsl_ns!{@exp ($state: $State) -> $Type { $pat => $body }}),*]);
-        }
-    };
-    // Symbols only.
-    (@word ($state:ident: $State:ty) -> $Type:ty {
-        $word:literal => $body:expr
-    }) => {
-        ($word, |$state|Ok(Some($body)))
-    };
-    // Expression handlers only.
-    (@exp ($state:ident: $State:ty) -> $Type:ty {
-        ($head:literal $(,$arg:ident:$ty:ty)* $(,)*) => $body:expr
-    }) => { ($head, |$state, tail: &str|{
-        $(
-            let head = tail.head()?.unwrap_or_default();
-            let tail = tail.tail()?.unwrap_or_default();
-            let $arg: $ty = if let Some(arg) = $state.from(&head)? {
-                arg
-            } else {
-                return Err(format!("{}: missing argument: {} ({}); got: {tail}",
-                    $head,
-                    stringify!($arg),
-                    stringify!($Type),
-                ).into())
-            };
-        )*
-        Ok(Some($body))
-    }) };
-    // Nothing else in symbols.
-    (@word ($state:ident: $State:ty) -> $Type:ty { $pat:tt => $body:expr }) => {
-        ("", |_|Ok(None)) // FIXME don't emit at all
-    };
-    // Nothing else in expression handlers.
-    (@exp ($state:ident: $State:ty) -> $Type:ty { $pat:tt => $body:expr }) => {
-        ("", |_, _|Ok(None)) // FIXME don't emit at all
-    };
-
-);
-
-pub trait DslNs<'t, T: 't>: 't {
-    /// Resolve an expression or symbol.
-    fn from <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
-        if let Ok(Some(src)) = dsl.src() {
-            if let Ok(Some(src)) = src.word() {
-                self.from_word(src)
-            } else {
-                self.from_expr(src)
-            }
-        } else {
-            Ok(None)
-        }
-    }
-    /// Resolve a symbol if known.
-    fn from_word <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
-        if let Some(dsl) = dsl.word()? {
-            for (word, get) in Self::WORDS.0 { if dsl == *word { return get(self) } }
-        }
-        return Ok(None)
-    }
-    /// Resolve an expression if known.
-    fn from_expr <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
-        if let Some(head) = dsl.expr().head()? {
-            for (key, value) in Self::EXPRS.0.iter() {
-                if head == *key {
-                    return value(self, dsl.expr().tail()?.unwrap_or(""))
-                }
-            }
-        }
-        return Ok(None)
-    }
-    /// Known symbols.
-    const WORDS: DslNsMap<'t, fn (&'t Self)->Perhaps<T>> = DslNsMap::new(&[]);
-    /// Known expressions.
-    const EXPRS: DslNsMap<'t, fn (&'t Self, &str)->Perhaps<T>> = DslNsMap::new(&[]);
-}
-/// Namespace mapping.
-#[derive(Debug)]
-pub struct DslNsMap<'t, T: Debug + 't>(pub &'t [(&'t str, T)]);
-impl<'t, T: Debug + 't> DslNsMap<'t, T> {
-    /// Populate a namespace.
-    pub const fn new (data: &'t [(&'t str, T)]) -> Self {
-        Self(data) // TODO build search index
-    }
-}

dsl/src/dsl_src.rs

@@ -1,21 +0,0 @@
-use crate::*;
-// Designates a string as parsable DSL.
-flex_trait!(Dsl: Debug + Send + Sync + Sized {
-    fn src (&self) -> DslPerhaps<&str> { unreachable!("Dsl::src default impl") }
-});
-// Some things that can be DSL source:
-impl Dsl for String {
-    fn src (&self) -> DslPerhaps<&str> { Ok(Some(self.as_ref())) }
-}
-impl Dsl for Arc<str> {
-    fn src (&self) -> DslPerhaps<&str> { Ok(Some(self.as_ref())) }
-}
-impl<'s> Dsl for &'s str  {
-    fn src (&self) -> DslPerhaps<&str> { Ok(Some(self.as_ref())) }
-}
-impl<D: Dsl> Dsl for Option<D> {
-    fn src (&self) -> DslPerhaps<&str> {Ok(if let Some(dsl) = self { dsl.src()? } else { None })}
-}
-impl<D: Dsl> Dsl for Result<D, DslError> {
-    fn src (&self) -> DslPerhaps<&str> {match self {Ok(dsl) => Ok(dsl.src()?), Err(e) => Err(*e)}}
-}