From e791ad57bcf2cb4460e254b458a631b5a5a48351 Mon Sep 17 00:00:00 2001
From: Bryan Newbold <bnewbold@robocracy.org>
Date: Mon, 25 Oct 2021 00:22:25 -0700
Subject: crate-local Result alias for less verbose type signatures

---
 src/cexpr.rs | 43 ++++++++++++++++++++-----------------------
 src/lib.rs   |  2 ++
 2 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/src/cexpr.rs b/src/cexpr.rs
index 357caff..5a171bd 100644
--- a/src/cexpr.rs
+++ b/src/cexpr.rs
@@ -5,6 +5,7 @@
  */
 
 use crate::sexpr::SExpr;
+use crate::Result;
 use std::fmt;
 
 #[derive(Debug, Clone, PartialEq, PartialOrd)]
@@ -46,7 +47,7 @@ pub enum CNumber {
 }
 
 impl CNumber {
-    pub fn to_sexpr(&self) -> Result<SExpr, String> {
+    pub fn to_sexpr(&self) -> Result<SExpr> {
         match self {
             CNumber::Integer(v) => Ok(SExpr::SInteger(*v)),
             CNumber::Rational(a, b) => Ok(SExpr::SList(vec![
@@ -123,7 +124,7 @@ fn compute_factorial(n: i64) -> i64 {
 }
 
 impl CExpr {
-    pub fn from_sexpr(sexpr: &SExpr) -> Result<CExpr, String> {
+    pub fn from_sexpr(sexpr: &SExpr) -> Result<CExpr> {
         // not all cases are handled; some atoms are covered trivialy
         match sexpr {
             SExpr::SNull => Err("null not handled".to_string()),
@@ -141,7 +142,7 @@ impl CExpr {
         }
     }
 
-    pub fn from_sexpr_list(list: &Vec<SExpr>) -> Result<CExpr, String> {
+    pub fn from_sexpr_list(list: &Vec<SExpr>) -> Result<CExpr> {
         use CExpr::*;
         use CNumber::*;
         use SExpr::*;
@@ -200,20 +201,16 @@ impl CExpr {
                     }
                 },
                 // TODO: how to make range unbounded? or less bounded?
-                ("+", 2..=5000) => {
-                    CExpr::new_sum(rest.iter().map(|v| CExpr::from_sexpr(v)).collect::<Result<
-                        Vec<CExpr>,
-                        String,
-                    >>(
-                    )?)
-                }
-                ("*", 2..=5000) => {
-                    CExpr::new_product(rest.iter().map(|v| CExpr::from_sexpr(v)).collect::<Result<
-                        Vec<CExpr>,
-                        String,
-                    >>(
-                    )?)
-                }
+                ("+", 2..=5000) => CExpr::new_sum(
+                    rest.iter()
+                        .map(|v| CExpr::from_sexpr(v))
+                        .collect::<Result<Vec<CExpr>>>()?,
+                ),
+                ("*", 2..=5000) => CExpr::new_product(
+                    rest.iter()
+                        .map(|v| CExpr::from_sexpr(v))
+                        .collect::<Result<Vec<CExpr>>>()?,
+                ),
                 ("-", 2) => {
                     let a = CExpr::from_sexpr(&rest[0])?;
                     let b = CExpr::from_sexpr(&rest[1])?;
@@ -236,7 +233,7 @@ impl CExpr {
         }
     }
 
-    pub fn new_sum(list: Vec<CExpr>) -> Result<CExpr, String> {
+    pub fn new_sum(list: Vec<CExpr>) -> Result<CExpr> {
         use CExpr::*;
         use CNumber::*;
         let (numeric, mut rest): (Vec<CExpr>, Vec<CExpr>) = list
@@ -273,7 +270,7 @@ impl CExpr {
         }
     }
 
-    pub fn new_product(list: Vec<CExpr>) -> Result<CExpr, String> {
+    pub fn new_product(list: Vec<CExpr>) -> Result<CExpr> {
         use CExpr::*;
         use CNumber::*;
         let (numeric, mut rest): (Vec<CExpr>, Vec<CExpr>) = list
@@ -310,7 +307,7 @@ impl CExpr {
         }
     }
 
-    pub fn to_sexpr(&self) -> Result<SExpr, String> {
+    pub fn to_sexpr(&self) -> Result<SExpr> {
         match self {
             CExpr::Symbol(s) => Ok(SExpr::SIdentifier(s.to_string())),
             CExpr::Number(n) => n.to_sexpr(),
@@ -319,7 +316,7 @@ impl CExpr {
                 let mut list = l
                     .iter()
                     .map(|v| v.to_sexpr())
-                    .collect::<Result<Vec<SExpr>, String>>()?;
+                    .collect::<Result<Vec<SExpr>>>()?;
                 list.insert(0, SExpr::SIdentifier("+".to_string()));
                 if let Some(num) = n {
                     list.insert(1, num.to_sexpr()?);
@@ -330,7 +327,7 @@ impl CExpr {
                 let mut list = l
                     .iter()
                     .map(|v| v.to_sexpr())
-                    .collect::<Result<Vec<SExpr>, String>>()?;
+                    .collect::<Result<Vec<SExpr>>>()?;
                 list.insert(0, SExpr::SIdentifier("*".to_string()));
                 if let Some(num) = n {
                     list.insert(1, num.to_sexpr()?);
@@ -353,7 +350,7 @@ impl CExpr {
         }
     }
 
-    pub fn from_str(raw: &str) -> Result<CExpr, String> {
+    pub fn from_str(raw: &str) -> Result<CExpr> {
         let ast = SExpr::from_str(raw)?;
         CExpr::from_sexpr(&ast)
     }
diff --git a/src/lib.rs b/src/lib.rs
index 950329b..4137840 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,6 +7,8 @@ mod sexpr;
 pub use cexpr::{CExpr, CNumber};
 pub use sexpr::{sexpr_parse_file, SExpr};
 
+pub type Result<T, E = String> = std::result::Result<T, E>;
+
 pub fn repl(_verbose: bool) {
     let stdin = io::stdin();
     let mut stdout = io::stdout();
-- 
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