add Ascend/Descend nodes to AST,Parser&Lexer

lib-ltcore/src/expr.rs

@@ -54,6 +54,14 @@ pub enum LTExpr {
         typ: Option<TypeTag>,
         symbol: String,
     },
+    Ascend {
+        typ: TypeTag,
+        expr: Box<LTExpr>
+    },
+    Descend {
+        typ: TypeTag,
+        expr: Box<LTExpr>
+    },
     Application {
         typ: Option<TypeTag>,
         head: Box<LTExpr>,

lib-ltcore/src/lexer.rs

@@ -16,6 +16,9 @@ pub enum LTIRToken {
     ExprOpen,
     ExprClose,
 
+    Ascend(String),
+    Descend(String),
+
     BlockOpen,
     BlockClose,
     StatementSep,
@@ -36,7 +39,10 @@ pub enum LexerState {
     Sym(String),
     Num(i64),
     Char(Option<char>),
-    DoubleQuote(String)
+    DoubleQuote(String),
+
+    Ascend(String),
+    Descend(String)
 }
 
 impl LexerState {
@@ -48,7 +54,9 @@ impl LexerState {
             LexerState::Sym(s) => Some(LTIRToken::Symbol(s)),
             LexerState::Num(n) => Some(LTIRToken::Num(n)),
             LexerState::Char(c) => Some(LTIRToken::Char(c?)),
-            LexerState::DoubleQuote(s) => Some(LTIRToken::DoubleQuote(s))
+            LexerState::DoubleQuote(s) => Some(LTIRToken::DoubleQuote(s)),
+            LexerState::Ascend(s) => Some(LTIRToken::Ascend(s)),
+            LexerState::Descend(s) => Some(LTIRToken::Descend(s))
         }
     }
 }
@@ -329,6 +337,19 @@ where
                     }
                 }
 
+                LexerState::Ascend(s) |
+                LexerState::Descend(s) => {
+                    if *c == ')' {
+                        let token = state.clone().into_token().unwrap();
+                        return Some((region, Ok(token)));
+                    } else {
+                        if let Some(c) = self.chars.next() {
+                            self.position += 1;
+                            region.end += 1;
+                            s.push(c);
+                        }
+                    }
+                }
                 _ => {
                     if c.is_whitespace()
                         || *c == '('
@@ -341,6 +362,24 @@ where
                         || *c == '↦'
                     {
                         // finish the current token
+                        match &mut state {
+                            LexerState::Sym(s) => {
+                                match s.as_str(){ 
+                                    "as"=> {
+                                        self.chars.next();
+                                        state = LexerState::Ascend(String::new());
+                                        continue;
+                                    }
+                                    "des" => {
+                                        self.chars.next();
+                                        state = LexerState::Descend(String::new());
+                                        continue;
+                                    }
+                                    _ =>{}
+                                }
+                            }
+                            _ => {}
+                        }
 
                         if let Some(token) = state.clone().into_token() {
                             return Some((region, Ok(token)));

lib-ltcore/src/parser.rs

@@ -351,6 +351,40 @@ where It: Iterator<Item = (InputRegionTag, Result<LTIRToken, LexError>)>
                 tokens.next();
                 children.push(LTExpr::StringLiteral{ region, value });
             }
+            Ok(LTIRToken::Ascend(type_str)) => {
+                let region = region.clone();
+                let typ =
+                    match typectx.write().unwrap().parse(type_str) {
+                        Ok(t) => Ok(t),
+                        Err(e) => Err(TypeError::ParseError(e))
+                    };
+
+                if let Some(expr) = children.pop() {
+                    children.push(LTExpr::Ascend {
+                        typ,
+                        expr: Box::new(expr)
+                    });
+                }
+
+                tokens.next();
+            }
+            Ok(LTIRToken::Descend(type_str)) => {
+                let region = region.clone();
+                let typ =
+                    match typectx.write().unwrap().parse(type_str) {
+                        Ok(t) => Ok(t),
+                        Err(e) => Err(TypeError::ParseError(e))
+                    };
+
+                if let Some(expr) = children.pop() {
+                    children.push(LTExpr::Descend {
+                        typ,
+                        expr: Box::new(expr)
+                    });
+                }
+
+                tokens.next();
+            }
             Ok(LTIRToken::Symbol(name)) => match name.as_str() {
                 "if" => {
                     tokens.next();

lib-ltcore/src/procedure_compiler.rs

@@ -234,6 +234,12 @@ impl ProcedureCompiler {
             LTExpr::WordLiteral { typ, val } => {
                 self.asm = self.asm.lit(*val);
             }
+            LTExpr::Ascend { typ, expr } => {
+                self = self.compile(expr);
+            }
+            LTExpr::Descend { typ, expr } => {
+                self = self.compile(expr);
+            }
             LTExpr::Application { typ, head, body } => {                
                 for arg in body.iter().rev() {
                     self = self.compile(arg);

lt-stdlib/ratio.lt

@@ -25,11 +25,11 @@ export {
         {bp:ℕ; bq:ℕ;}: ℚ ~ <Ratio ℕ ~ ℤ_2^64 ~ machine.UInt64> ;
     } ↦ {
         let l = lcm aq bq;
-        let as = i/ l aq;
+        let a = i/ l aq;
-        let bs = i/ l bq;
+        let b = i/ l bq;
 
-        i* aq as;
+        i* aq a;
-        i+ (i* ap as) (i* bp bs);
+        i+ (i* ap a) (i* bp b);
     };
 
     let ratio-mul = λ{