From c724c9157dbc4721fa8ed93033cd9699c9652277 Mon Sep 17 00:00:00 2001
From: Ben Bridle <ben@derelict.engineering>
Date: Sat, 12 Apr 2025 10:08:09 +1200
Subject: Implement negative integer literals

Negative literals take the forms -29, -0x1D, and -0b11101 for decimal,
hexadecimal, and binary.
---
 src/stages/syntactic.rs | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

(limited to 'src')

diff --git a/src/stages/syntactic.rs b/src/stages/syntactic.rs
index 14f8815..45d5e60 100644
--- a/src/stages/syntactic.rs
+++ b/src/stages/syntactic.rs
@@ -168,22 +168,27 @@ fn parse_syntactic_from_tokeniser(mut t: Tokeniser) -> Result<Vec<Tracked<Syntac
 
             c => {
                 let token = format!("{c}{}", t.eat_token());
-                if let Some(hex_string) = token.strip_prefix("0x") {
+                let (stripped, neg) = match token.strip_prefix('-') {
+                    Some(stripped) => (stripped, true),
+                    None => (token.as_str(), false),
+                };
+                if let Some(hex_string) = stripped.strip_prefix("0x") {
                     let hex_string = hex_string.to_string();
-                    match parse_integer_literal(&hex_string, 16) {
+                    match parse_integer_literal(&hex_string, 16, neg) {
                         Ok(value) => SyntacticToken::IntegerLiteral(value),
                         Err(_) => err!(SyntacticError::InvalidHexadecimalLiteral(hex_string)),
                     }
-                } else if let Some(binary_string) = token.strip_prefix("0b") {
+                } else if let Some(binary_string) = stripped.strip_prefix("0b") {
                     let binary_string = binary_string.to_string();
-                    match parse_integer_literal(&binary_string, 2) {
+                    match parse_integer_literal(&binary_string, 2, neg) {
                         Ok(value) => SyntacticToken::IntegerLiteral(value),
                         Err(_) => err!(SyntacticError::InvalidBinaryLiteral(binary_string)),
                     }
                 } else {
-                    match parse_integer_literal(&token, 10) {
+                    let decimal_string = stripped.to_string();
+                    match parse_integer_literal(&decimal_string, 10, neg) {
                         Ok(value) => SyntacticToken::IntegerLiteral(value),
-                        Err(true) => err!(SyntacticError::InvalidDecimalLiteral(token)),
+                        Err(true) => err!(SyntacticError::InvalidDecimalLiteral(decimal_string)),
                         Err(false) => SyntacticToken::Symbol(ScopedSymbol::Global(token)),
                     }
                 }
@@ -200,10 +205,13 @@ fn parse_syntactic_from_tokeniser(mut t: Tokeniser) -> Result<Vec<Tracked<Syntac
 }
 
 
-fn parse_integer_literal(token: &str, radix: u32) -> Result<isize, bool> {
+fn parse_integer_literal(token: &str, radix: u32, neg: bool) -> Result<isize, bool> {
     match usize::from_str_radix(&token.replace('_', ""), radix) {
         Ok(value) => match isize::try_from(value) {
-            Ok(value) => Ok(value),
+            Ok(value) => match neg {
+                true => Ok(-value),
+                false => Ok(value),
+            }
             Err(_) => Err(true),
         }
         Err(_) => Err(false),
-- 
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