From 1f5c3214b2855659079bd65dd6a45bb5762d8dd7 Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Sat, 27 Mar 2021 13:16:01 +0530
Subject: add arity struct for primitives

---
 src/lisp/expr.rs   | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++----
 src/lisp/number.rs | 21 ++++++++++++
 2 files changed, 108 insertions(+), 7 deletions(-)

diff --git a/src/lisp/expr.rs b/src/lisp/expr.rs
index acd3365..40420a1 100644
--- a/src/lisp/expr.rs
+++ b/src/lisp/expr.rs
@@ -3,21 +3,45 @@ use std::{convert::TryFrom, fmt};
 use crate::app::AppState;
 use crate::lisp::{
     error::{EvalError, LispError},
+    eval::lookup_extended,
     number::LispNumber,
+    EnvList, Environment,
 };
 
+#[derive(Debug, Copy, PartialEq, Clone)]
+pub enum Arity {
+    Exact(usize),
+    Atleast(usize),
+    Atmost(usize),
+    Range(usize, usize),
+    None,
+}
+
+impl Arity {
+    pub fn is_valid<T>(self, args: &[T]) -> bool {
+        match self {
+            Arity::Exact(a) => args.len() == a,
+            Arity::Atleast(a) => args.len() >= a,
+            Arity::Atmost(a) => args.len() <= a,
+            Arity::Range(low, high) => args.len() >= low && args.len() <= high,
+            Arity::None => true,
+        }
+    }
+    pub fn to_error(self) -> LispError {
+        LispError::Eval(EvalError::ArgumentCount(self))
+    }
+}
+
 #[derive(Clone)]
 pub struct PrimitiveFunc {
-    pub arity: Option<usize>, // minimim arity
+    pub arity: Arity, // minimim arity
     pub closure: fn(&[LispExpr], &mut AppState) -> Result<LispExpr, LispError>,
 }
 
 impl PrimitiveFunc {
     pub fn call(&self, args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
-        if let Some(arity) = self.arity {
-            if args.len() < arity {
-                return Err(EvalError::ArgumentCount(self.arity.map(|u| u as u32)).into());
-            }
+        if !self.arity.is_valid(args) {
+            return Err(EvalError::ArgumentCount(self.arity).into());
         }
         (self.closure)(args, app)
     }
@@ -42,6 +66,7 @@ pub enum LispExpr {
     Ident(Ident),
     PrimitiveFunc(PrimitiveFunc),
     Function(LispFunction),
+    Char(char),
 
     // none of these depths should be zero
     Quasiquote(Box<LispExpr>, u32),
@@ -83,6 +108,40 @@ impl LispExpr {
             v => LispExpr::Quasiquote(Box::new(v), n),
         }
     }
+
+    pub fn compare(&self, other: &Self, envs: &EnvList) -> Result<BoolLit, LispError> {
+        match (self, other) {
+            (LispExpr::Unit, LispExpr::Unit) => Ok(true),
+            (LispExpr::Number(s), LispExpr::Number(o)) => Ok(s == o),
+            (LispExpr::List(s), LispExpr::List(o)) => Ok(s
+                .iter()
+                .zip(o)
+                .all(|(a, b)| matches!(a.compare(b, envs), Ok(true)))),
+            (LispExpr::StringLit(s), LispExpr::StringLit(o)) => Ok(s == o),
+            (LispExpr::Char(s), LispExpr::Char(o)) => Ok(s == o),
+            (LispExpr::BoolLit(s), LispExpr::BoolLit(o)) => Ok(s == o),
+            (LispExpr::Ident(s), LispExpr::Ident(o)) => {
+                let s = lookup_extended(envs, s)?;
+                let o = lookup_extended(envs, o)?;
+                s.compare(&o, envs)
+            }
+            (LispExpr::PrimitiveFunc(s), LispExpr::PrimitiveFunc(o)) => {
+                let PrimitiveFunc { closure: s, .. } = s;
+                let PrimitiveFunc { closure: o, .. } = o;
+                Ok(*s as usize == *o as usize)
+            }
+            (LispExpr::Function(_), LispExpr::Function(_)) => Err(EvalError::BadForm.into()),
+            (LispExpr::Quasiquote(s, sd), LispExpr::Quasiquote(o, od)) => {
+                Ok(s.compare(o, envs)? && sd == od)
+            }
+            (LispExpr::Comma(s, sd), LispExpr::Comma(o, od)) => Ok(s.compare(o, envs)? && sd == od),
+            (LispExpr::CommaAt(s, sd), LispExpr::CommaAt(o, od)) => {
+                Ok(s.compare(o, envs)? && sd == od)
+            }
+            (LispExpr::Quote(s, sd), LispExpr::Quote(o, od)) => Ok(s.compare(o, envs)? && sd == od),
+            _ => Err(EvalError::TypeMismatch.into()),
+        }
+    }
 }
 
 impl fmt::Display for LispExpr {
@@ -96,6 +155,7 @@ impl fmt::Display for LispExpr {
                 }
             }
             LispExpr::StringLit(s) => write!(f, "{}", s)?,
+            LispExpr::Char(c) => write!(f, "{}", c)?,
             LispExpr::BoolLit(b) => {
                 if *b {
                     write!(f, "#t")?
@@ -137,16 +197,36 @@ impl<'a> TryFrom<&'a LispExpr> for &'a LispNumber {
     }
 }
 
-impl TryFrom<LispExpr> for Ident {
+//impl TryFrom<LispExpr> for Ident {
+//    type Error = LispError;
+//    fn try_from(value: LispExpr) -> Result<Self, Self::Error> {
+//        match value {
+//            LispExpr::Ident(i) => Ok(i),
+//            _ => Err(LispError::Eval(EvalError::TypeMismatch)),
+//        }
+//    }
+//}
+//
+//
+impl TryFrom<LispExpr> for String {
     type Error = LispError;
     fn try_from(value: LispExpr) -> Result<Self, Self::Error> {
         match value {
-            LispExpr::Ident(i) => Ok(i),
+            LispExpr::StringLit(i) => Ok(i),
             _ => Err(LispError::Eval(EvalError::TypeMismatch)),
         }
     }
 }
 
+impl AsRef<str> for LispExpr {
+    fn as_ref(&self) -> &str {
+        match self {
+            LispExpr::StringLit(i) => &i,
+            _ => panic!("invalid downcast!"),
+        }
+    }
+}
+
 impl TryFrom<LispExpr> for BoolLit {
     type Error = LispError;
     fn try_from(value: LispExpr) -> Result<Self, Self::Error> {
diff --git a/src/lisp/number.rs b/src/lisp/number.rs
index 23d7997..0ce5ac0 100644
--- a/src/lisp/number.rs
+++ b/src/lisp/number.rs
@@ -1,4 +1,5 @@
 use std::{
+    cmp::{Eq, Ord, Ordering, PartialEq, PartialOrd},
     fmt,
     ops::{Add, Mul, Sub},
 };
@@ -78,6 +79,26 @@ impl PartialEq for LispNumber {
     }
 }
 
+impl Eq for LispNumber {}
+
+impl Ord for LispNumber {
+    fn cmp(&self, other: &Self) -> Ordering {
+        use LispNumber::*;
+        match (*self, *other) {
+            (Integer(a), Integer(b)) => a.cmp(&b),
+            (Float(a), Integer(b)) => (a as i64).cmp(&b),
+            (Integer(a), Float(b)) => a.cmp(&(b as i64)),
+            (Float(a), Float(b)) => (a as i64).cmp(&(b as i64)),
+        }
+    }
+}
+
+impl PartialOrd for LispNumber {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
 impl fmt::Display for LispNumber {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
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