wip: dsl refactor

dsl/src/dsl.rs

@@ -6,12 +6,18 @@
 extern crate const_panic;
 use const_panic::PanicFmt;
 use std::fmt::Debug;
-pub(crate) use std::{error::Error, sync::Arc};
+pub(crate) use ::{
-pub(crate) use konst::{iter::for_each, string::{str_from, str_range, char_indices}};
+    std::sync::Arc,
-pub(crate) use thiserror::Error;
+    std::error::Error,
-pub(crate) use ::tengri_core::*;
+    konst::iter::for_each,
+    konst::string::{str_from, str_range, char_indices},
+    thiserror::Error,
+    tengri_core::*
+};
 pub(crate) use self::DslError::*;
 mod dsl_conv; pub use self::dsl_conv::*;
+mod dsl_ns;   pub use self::dsl_ns::*;
+mod dsl_type;
 #[cfg(test)] mod dsl_test;
 /// DSL-specific result type.
 pub type DslResult<T> = Result<T, DslError>;
@@ -21,42 +27,41 @@ pub type DslPerhaps<T> = Result<Option<T>, DslError>;
 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())) } }
+
 // Designates a string as parsable DSL.
-flex_trait!(Dsl: Debug + Send + Sync + Sized {
+flex_trait!(Dsl: Debug + Send + Sync + Sized { fn src (&self) -> DslPerhaps<&str> { unreachable!("Dsl::src default impl") } });
-    fn src (&self) -> DslPerhaps<&str> { unreachable!("Dsl::src default impl") }
-});
 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)}}
 }
-impl<D: Dsl> DslText for D {} pub trait DslText: Dsl {
+
-    fn text (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(text_peek_only))}
+/// DSL-specific error codes.
+#[derive(Error, Debug, Copy, Clone, PartialEq, PanicFmt)]
+pub enum DslError {
+    #[error("parse failed: not implemented")] Unimplemented,
+    #[error("parse failed: empty")] Empty,
+    #[error("parse failed: incomplete")] Incomplete,
+    #[error("parse failed: unexpected character '{0}'")] Unexpected(char, Option<usize>, Option<&'static str>),
+    #[error("parse failed: error #{0}")] Code(u8),
+    #[error("end reached")] End
 }
-impl<D: Dsl> DslSym for D {} pub trait DslSym: Dsl {
+
-    fn sym  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(sym_peek_only))}
+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')
 }
-impl<D: Dsl> DslKey for D {} pub trait DslKey: Dsl {
+pub const fn no_trailing_non_space (src: &str, offset: usize, context: Option<&'static str>) -> DslResult<()> {
-    fn key  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(key_peek_only))}
+    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 {
-impl<D: Dsl> DslNum for D {} pub trait DslNum: Dsl {
+            Some(context)
-    fn num  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(num_peek_only))}
+        } else {
-}
+            Some("trailing non-space")
-impl<D: Dsl> DslExp for D {} pub trait DslExp: Dsl {
+        }))
-    fn exp  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(exp_peek_inner_only))}
+    }))
-    fn head (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(peek))}
-    fn tail (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(peek_tail))}
-    /// my other car is a cdr :<
-    fn each (&self, mut cb: impl FnMut(&str)->Usually<()>) -> Usually<()> {
-        Ok(if let Some(head) = self.head()? {
-            cb(head)?;
-            if let Some(tail) = self.tail()? {
-                tail.each(cb)?;
-            }
-        })
-    }
 }
+
 pub const fn peek (src: &str) -> DslPerhaps<&str> {
     Ok(Some(if let Ok(Some(exp))  = exp_peek(src)  { exp  } else
             if let Ok(Some(sym))  = sym_peek(src)  { sym  } else
@@ -86,185 +91,160 @@ pub const fn peek_tail (src: &str) -> DslPerhaps<&str> {
         },
     }
 }
-/// DSL-specific error codes.
+
-#[derive(Error, Debug, Copy, Clone, PartialEq, PanicFmt)]
+pub const fn is_exp_start (c: char) -> bool { c == '(' }
-pub enum DslError {
+pub const fn is_exp_end (c: char) -> bool { c == ')' }
-    #[error("parse failed: not implemented")] Unimplemented,
+dsl_type!(DslExp {
-    #[error("parse failed: empty")] Empty,
+    fn exp  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(exp_peek_inner_only))}
-    #[error("parse failed: incomplete")] Incomplete,
+    fn head (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(peek))}
-    #[error("parse failed: unexpected character '{0}'")] Unexpected(char, Option<usize>, Option<&'static str>),
+    fn tail (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(peek_tail))}
-    #[error("parse failed: error #{0}")] Code(u8),
+    /// my other car is a cdr :<
-    #[error("end reached")] End
+    fn each (&self, mut cb: impl FnMut(&str)->Usually<()>) -> Usually<()> {
-}
+        Ok(if let Some(head) = self.head()? {
-fn ok_flat <T> (x: Option<DslPerhaps<T>>) -> DslPerhaps<T> { Ok(x.transpose()?.flatten()) }
+            cb(head)?;
-pub const fn is_space (c: char) -> bool {
+            if let Some(tail) = self.tail()? {
-    matches!(c, ' '|'\n'|'\r'|'\t')
+                tail.each(cb)?;
-}
-pub const fn no_trailing_non_space (source: &str, offset: usize, context: Option<&'static str>) -> DslResult<()> {
-    Ok(for_each!((i, c) in char_indices(str_range(source, offset, source.len())) => if !is_space(c) {
-        return Err(Unexpected(c, Some(offset + i), if let Some(context) = context {
-            Some(context)
-        } else {
-            Some("trailing non-space")
-        }))
-    }))
-}
-macro_rules! def_peek_seek(($peek:ident, $peek_only:ident, $seek:ident, $seek_start:ident, $seek_length:ident)=>{
-    /// Find a slice corrensponding to a syntax token.
-    pub const fn $peek (source: &str) -> DslPerhaps<&str> {
-        match $seek(source) {
-            Err(e) => Err(e),
-            Ok(None) => Ok(None),
-            Ok(Some((start, length))) => Ok(Some(str_range(source, start, start + length))),
-        }
-    }
-    /// Find a slice corrensponding to a syntax token
-    /// but return an error if it isn't the only thing
-    /// in the source.
-    pub const fn $peek_only (source: &str) -> DslPerhaps<&str> {
-        match $seek(source) {
-            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) }
-                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)> {
+    pub const fn exp_peek      [generated];
-        match $seek_start(source) {
+    pub const fn exp_peek_only [generated];
-            Err(e) => Err(e),
+    pub const fn exp_seek      [generated];
-            Ok(None) => Ok(None),
+    pub const fn exp_seek_start (src) {
-            Ok(Some(start)) => match $seek_length(str_from(source, start)) {
+        for_each!((i, c) in char_indices(src) =>
-                Ok(Some(length)) => Ok(Some((start, length))),
+            if is_exp_start(c) { return Ok(Some(i)) } else
-                Ok(None) => Ok(None),
+            if !is_space(c) { return Err(Unexpected(c, Some(i), Some("expected expression start"))) });
-                Err(e) => Err(e),
+        Ok(None)
-            },
+    }
-        }
+    pub const fn exp_seek_length (src) {
+        let mut depth = 0;
+        for_each!((i, c) in char_indices(src) =>
+            if is_exp_start(c) { depth += 1; } else
+            if is_exp_end(c) {
+                if depth == 0 {
+                    return Err(Unexpected(c, Some(i), Some("expected expression end")))
+                } else if depth == 1 {
+                    return Ok(Some(i + 1))
+                } else {
+                    depth -= 1;
+                }
+            });
+        Err(Incomplete)
     }
 });
-def_peek_seek!(exp_peek, exp_peek_only, exp_seek, exp_seek_start, exp_seek_length);
+
-pub const fn exp_peek_inner (source: &str) -> DslPerhaps<&str> {
+pub const fn exp_peek_inner (src: &str) -> DslPerhaps<&str> {
-    match exp_peek(source) {
+    match exp_peek(src) {
         Ok(Some(peeked)) => {
             let len = peeked.len();
             let start = if len > 0 { 1 } else { 0 };
-            Ok(Some(str_range(source, start, start + len.saturating_sub(2))))
+            Ok(Some(str_range(src, start, start + len.saturating_sub(2))))
         },
         e => e
     }
 }
-pub const fn exp_peek_inner_only (source: &str) -> DslPerhaps<&str> {
+
-    match exp_seek(source) {
+pub const fn exp_peek_inner_only (src: &str) -> DslPerhaps<&str> {
+    match exp_seek(src) {
         Err(e) => Err(e),
         Ok(None) => Ok(None),
         Ok(Some((start, length))) => {
-            if let Err(e) = no_trailing_non_space(source, start + length, Some("exp_peek_inner_only")) { return Err(e) }
+            if let Err(e) = no_trailing_non_space(src, start + length, Some("exp_peek_inner_only")) { return Err(e) }
-            let peeked = str_range(source, start, start + length);
+            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_exp_start (c: char) -> bool { c == '(' }
+
-pub const fn is_exp_end (c: char) -> bool { c == ')' }
-pub const fn exp_seek_start (source: &str) -> DslPerhaps<usize> {
-    for_each!((i, c) in char_indices(source) => if is_exp_start(c) {
-        return Ok(Some(i))
-    } else if !is_space(c) {
-        return Err(Unexpected(c, Some(i), Some("expected expression start")))
-    });
-    Ok(None)
-}
-pub const fn exp_seek_length (source: &str) -> DslPerhaps<usize> {
-    let mut depth = 0;
-    for_each!((i, c) in char_indices(source) => if is_exp_start(c) {
-        depth += 1;
-    } else if is_exp_end(c) {
-        if depth == 0 {
-            return Err(Unexpected(c, Some(i), Some("expected expression end")))
-        } else if depth == 1 {
-            return Ok(Some(i + 1))
-        } else {
-            depth -= 1;
-        }
-    });
-    Err(Incomplete)
-}
-def_peek_seek!(sym_peek, sym_peek_only, sym_seek, sym_seek_start, sym_seek_length);
 pub const fn is_sym_start (c: char) -> bool { matches!(c, ':'|'@') }
 pub const fn is_sym_char (c: char) -> bool { is_sym_start(c) || matches!(c, 'a'..='z'|'A'..='Z'|'0'..='9'|'-'|'/') }
 pub const fn is_sym_end (c: char) -> bool { is_space(c) || matches!(c, ')') }
-pub const fn sym_seek_start (source: &str) -> DslPerhaps<usize> {
+dsl_type!(DslSym {
-    for_each!((i, c) in char_indices(source) => if is_sym_start(c) {
+    fn sym (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(sym_peek_only))}
-        return Ok(Some(i))
+} {
-    } else if !is_space(c) {
+    pub const fn sym_peek      [generated];
-        return Err(Unexpected(c, Some(i), Some("sym_seek_start")))
+    pub const fn sym_peek_only [generated];
-    });
+    pub const fn sym_seek      [generated];
-    Ok(None)
+    pub const fn sym_seek_start (src) {
-}
+        for_each!((i, c) in char_indices(src) => if
-pub const fn sym_seek_length (source: &str) -> DslPerhaps<usize> {
+            is_sym_start(c) { return Ok(Some(i)) } else
-    for_each!((i, c) in char_indices(source) => if is_sym_end(c) {
+            if !is_space(c) { return Err(Unexpected(c, Some(i), Some("sym_seek_start"))) });
-        return Ok(Some(i))
+        Ok(None)
-    } else if !is_sym_char(c) {
+    }
-        return Err(Unexpected(c, Some(i), Some("sym_seek_length")))
+    pub const fn sym_seek_length (src) {
-    });
+        for_each!((i, c) in char_indices(src) =>
-    Ok(Some(source.len()))
+            if is_sym_end(c) { return Ok(Some(i)) } else
-}
+            if !is_sym_char(c) { return Err(Unexpected(c, Some(i), Some("sym_seek_length"))) });
-def_peek_seek!(key_peek, key_peek_only, key_seek, key_seek_start, key_seek_length);
+        Ok(Some(src.len()))
-pub const fn is_key_start (c: char) -> bool { matches!(c, '/'|('a'..='z')) }
+    }
-pub const fn is_key_char (c: char) -> bool { matches!(c, 'a'..='z'|'0'..='9'|'-'|'/') }
+});
-pub const fn is_key_end (c: char) -> bool { is_space(c) || matches!(c, ')') }
+
-pub const fn key_seek_start (source: &str) -> DslPerhaps<usize> {
-    for_each!((i, c) in char_indices(source) => if is_key_start(c) {
-        return Ok(Some(i))
-    } else if !is_space(c) {
-        return Err(Unexpected(c, Some(i), None))
-    });
-    Ok(None)
-}
-pub const fn key_seek_length (source: &str) -> DslPerhaps<usize> {
-    for_each!((i, c) in char_indices(source) => if is_key_end(c) {
-        return Ok(Some(i))
-    } else if !is_key_char(c) {
-        return Err(Unexpected(c, Some(i), None))
-    });
-    Ok(Some(source.len()))
-}
-def_peek_seek!(text_peek, text_peek_only, text_seek, text_seek_start, text_seek_length);
 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 text_seek_start (source: &str) -> DslPerhaps<usize> {
+dsl_type!(DslText {
-    for_each!((i, c) in char_indices(source) => if is_text_start(c) {
+    fn text (&self) -> DslPerhaps<&str> { ok_flat(self.src()?.map(text_peek_only)) }
-        return Ok(Some(i))
+} {
-    } else if !is_space(c) {
+    pub const fn text_peek      [generated];
-        return Err(Unexpected(c, Some(i), None))
+    pub const fn text_peek_only [generated];
-    });
+    pub const fn text_seek      [generated];
-    Ok(None)
+    pub const fn text_seek_start (src) {
-}
+        for_each!((i, c) in char_indices(src) =>
-pub const fn text_seek_length (source: &str) -> DslPerhaps<usize> {
+            if is_text_start(c) { return Ok(Some(i)) } else
-    for_each!((i, c) in char_indices(source) => if is_text_end(c) { return Ok(Some(i)) });
+            if !is_space(c)     { return Err(Unexpected(c, Some(i), None)) });
-    Ok(None)
+        Ok(None)
-}
+    }
-def_peek_seek!(num_peek, num_peek_only, num_seek, num_seek_start, num_seek_length);
+    pub const fn text_seek_length (src) {
-pub const fn num_seek_start (source: &str) -> DslPerhaps<usize> {
+        for_each!((i, c) in char_indices(src) =>
-    for_each!((i, c) in char_indices(source) => if is_digit(c) {
+            if is_text_end(c) { return Ok(Some(i)) });
-        return Ok(Some(i));
+        Ok(None)
-    } else if !is_space(c) {
+    }
-        return Err(Unexpected(c, Some(i), None))
+});
-    });
+
-    Ok(None)
+pub const fn is_key_start (c: char) -> bool { matches!(c, '/'|('a'..='z')) }
-}
+pub const fn is_key_char (c: char) -> bool { is_key_start(c) || matches!(c, '0'..='9'|'-') }
-pub const fn num_seek_length (source: &str) -> DslPerhaps<usize> {
+pub const fn is_key_end (c: char) -> bool { !is_key_char(c) }
-    for_each!((i, c) in char_indices(source) => if is_num_end(c) {
+dsl_type!(DslKey {
-        return Ok(Some(i))
+    fn key (&self) -> DslPerhaps<&str> { ok_flat(self.src()?.map(key_peek_only)) }
-    } else if !is_digit(c) {
+} {
-        return Err(Unexpected(c, Some(i), None))
+    pub const fn key_peek      [generated];
-    });
+    pub const fn key_peek_only [generated];
-    Ok(None)
+    pub const fn key_seek      [generated];
-}
+    pub const fn key_seek_start (src) {
+        for_each!((i, c) in char_indices(src) =>
+            if is_key_start(c) { return Ok(Some(i)) } else
+            if !is_space(c)    { return Err(Unexpected(c, Some(i), None)) });
+        Ok(None)
+    }
+    pub const fn key_seek_length (src) {
+        for_each!((i, c) in char_indices(src) =>
+            if is_key_end(c)   { return Ok(Some(i)) } else
+            if !is_key_char(c) { return Err(Unexpected(c, Some(i), None)) });
+        Ok(Some(src.len()))
+    }
+});
+
+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 <D: Dsl> (digits: &str) -> Result<usize, DslError> {

dsl/src/dsl_conv.rs

@@ -1,51 +1,5 @@
 use crate::*;
 
-/// Namespace. Currently linearly searched.
-pub struct DslNs<'t, T: 't>(pub &'t [(&'t str, T)]);
-
-/// Namespace where keys are symbols.
-pub trait DslSymNs<'t, T: 't>: 't {
-    const SYMS: DslNs<'t, fn (&'t Self)->T>;
-    fn from_sym <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
-        if let Some(dsl) = dsl.sym()? {
-            for (sym, get) in Self::SYMS.0 {
-                if dsl == *sym {
-                    return Ok(Some(get(self)))
-                }
-            }
-        }
-        return Ok(None)
-    }
-}
-
-#[macro_export] macro_rules! dsl_sym (
-    (|$state:ident:$State:ty| -> $type:ty {$($lit:literal => $exp:expr),* $(,)?})=>{
-        impl<'t> DslSymNs<'t, $type> for $State {
-            const SYMS: DslNs<'t, fn (&'t $State)->$type> =
-                DslNs(&[$(($lit, |$state: &$State|$exp)),*]); } });
-
-pub trait DslExpNs<'t, T: 't>: 't {
-    const EXPS: DslNs<'t, fn (&'t Self, &str)->T>;
-    fn from_exp <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
-        if let Some(exp) = dsl.exp()? {
-            for (key, value) in Self::EXPS.0.iter() {
-                if exp.head() == Ok(Some(key)) {
-                    return Ok(Some(value(self, exp.tail()?.unwrap_or(""))))
-                }
-            }
-        }
-        return Ok(None)
-    }
-}
-
-#[macro_export] macro_rules! dsl_exp (
-    (|$state:ident:$State:ty$(, $tail:ident)?|->$type:ty { $(
-        ($key:literal $(/ $sub:ident: $Sub:ty)? $(, $arg:ident $(?)? :$argtype:ty)*) => $body:expr
-    ),* $(,)? }) => {
-        impl<'t> DslExpNs<'t, $type> for $State {
-            const EXPS: DslNs<'t, fn (&'t $State, &str)->$type> =
-                DslNs(&[]); } });
-
 // TODO DEPRECATE:
 
 /// `T` + [Dsl] -> `Self`.

dsl/src/dsl_ns.rs

@@ -0,0 +1,70 @@
+use crate::*;
+
+/// Define a symbol namespace.
+#[macro_export] macro_rules! dsl_sym_ns (
+    (|$state:ident:$State:ty| -> $type:ty {$($lit:literal => $exp:expr),* $(,)?})=>{
+        impl<'t> DslSymNs<'t, $type> for $State {
+            const SYMS: DslNs<'t, fn (&'t $State)->$type> = DslNs(&[
+                $(($lit, |$state: &$State|$exp)),*
+            ]);
+        }
+    });
+
+/// Define an expression namespace.
+#[macro_export] macro_rules! dsl_exp_ns (
+    (|$state:ident:$State:ty|->$type:ty { $( (
+        $key:literal
+        $(/ $sub:ident : $Sub:ty)?
+        $(, $arg:ident $(?)? : $argtype:ty)*
+        $(, ..$tail:ident)?
+    ) => $body:expr),* $(,)? }) => {
+        impl<'t> DslExpNs<'t, fn (&'t $State, &str)->$type> for $State {
+            const EXPS: DslNs<'t, fn (&'t $State, &str)->$type> = DslNs(&[ $(
+                ($key, |$state: &$State, mut tail: &str|{
+                    $(let $arg = dsl_next(&mut tail)?;)*
+                    $(let $tail = tail;)?
+                    $body
+                })
+            ),* ]);
+        }
+    });
+
+/// Namespace where keys are symbols.
+pub trait DslSymNs<'t, T: 't>: 't {
+    const SYMS: DslNs<'t, fn (&'t Self)->T> = DslNs(&[]);
+    fn from_sym <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
+        if let Some(dsl) = dsl.sym()? {
+            for (sym, get) in Self::SYMS.0 {
+                if dsl == *sym {
+                    return Ok(Some(get(self)))
+                }
+            }
+        }
+        return Ok(None)
+    }
+}
+
+/// Namespace where the keys are heads of expressions.
+pub trait DslExpNs<'t, T: 't>: 't {
+    const EXPS: DslNs<'t, fn (&'t Self, &str)->T> = DslNs(&[]);
+    fn from_exp <D: Dsl> (&'t self, dsl: D) -> Perhaps<T> {
+        if let Some(exp) = dsl.exp()? {
+            panic!("exp\n{:?}\n{:?}\n{:?}\n{:?}", exp.src(), exp.head(), exp.head().src(), Self::EXPS.0);
+            for (key, value) in Self::EXPS.0.iter() {
+                println!("{key} {:?}", exp.head());
+                if exp.head() == Ok(Some(key)) {
+                    return Ok(Some(value(self, exp.tail()?.unwrap_or(""))))
+                }
+            }
+        }
+        return Ok(None)
+    }
+}
+
+/// Namespace.
+///
+/// Currently linearly searched.
+/// Maybe it's better to use a trie.
+/// I don't think there's a `const` trie in Rust?
+/// Oughtta be.
+pub struct DslNs<'t, T: 't>(pub &'t [(&'t str, T)]);

dsl/src/dsl_type.rs

@@ -0,0 +1,51 @@
+use crate::*;
+
+#[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)?;
+    pub const fn $seek:ident      $($_3:tt)?;
+    pub const fn $seek_start:ident  ($source1:ident) $body1:block
+    pub const fn $seek_length:ident ($source2:ident) $body2:block
+})=>{
+    pub trait $T: Dsl { $($trait)* }
+    impl<D: Dsl> $T for D {} 
+    dsl_peek_seek!($peek, $peek_only, $seek, $seek_start, $seek_length);
+    pub const fn $seek_start  ($source1: &str) -> DslPerhaps<usize> $body1
+    pub const fn $seek_length ($source2: &str) -> DslPerhaps<usize> $body2
+});
+
+#[macro_export] macro_rules! dsl_peek_seek(($peek:ident, $peek_only:ident, $seek:ident, $seek_start:ident, $seek_length:ident)=>{
+    /// Find a slice corrensponding to a syntax token.
+    pub const fn $peek (source: &str) -> DslPerhaps<&str> {
+        match $seek(source) {
+            Err(e) => Err(e),
+            Ok(None) => Ok(None),
+            Ok(Some((start, length))) => Ok(Some(str_range(source, start, start + length))),
+        }
+    }
+    /// Find a slice corrensponding to a syntax token
+    /// but return an error if it isn't the only thing
+    /// in the source.
+    pub const fn $peek_only (source: &str) -> DslPerhaps<&str> {
+        match $seek(source) {
+            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) }
+                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),
+            },
+        }
+    }
+});

input/src/input_dsl.rs

@@ -128,9 +128,3 @@ impl<C> Binding<C> {
         }
     }
 }
-fn unquote (x: &str) -> &str {
-    let mut chars = x.chars();
-    chars.next();
-    //chars.next_back();
-    chars.as_str()
-}