From 5035362ee6d9cc311dfc907d09ae92de14560d0b Mon Sep 17 00:00:00 2001
From: Lachlan Sneff <lachlan.sneff@gmail.com>
Date: Thu, 20 Aug 2020 01:41:24 -0400
Subject: [PATCH] Better floating point support for wgsl (#142)

* Add custom consume_number function for consuming numbers into tokens to wgsl frontend

* clippy
---
 src/front/wgsl.rs | 49 ++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 42 insertions(+), 7 deletions(-)

diff --git a/src/front/wgsl.rs b/src/front/wgsl.rs
index 3c52952660..8ccdd41ad2 100644
--- a/src/front/wgsl.rs
+++ b/src/front/wgsl.rs
@@ -44,6 +44,28 @@ mod lex {
         input.split_at(pos)
     }
 
+    fn consume_number(input: &str) -> (&str, &str) {
+        let mut is_first_char = true;
+        let mut right_after_exponent = false;
+
+        let mut what = |c| {
+            if is_first_char {
+                is_first_char = false;
+                c == '-' || c >= '0' && c <= '9' || c == '.'
+            } else if c == 'e' || c == 'E' {
+                right_after_exponent = true;
+                true
+            } else if right_after_exponent {
+                right_after_exponent = false;
+                c >= '0' && c <= '9' || c == '-'
+            } else {
+                c >= '0' && c <= '9' || c == '.'
+            }
+        };
+        let pos = input.find(|c| !what(c)).unwrap_or_else(|| input.len());
+        input.split_at(pos)
+    }
+
     pub fn consume_token(mut input: &str) -> (Token<'_>, &str) {
         input = input.trim_start();
         let mut chars = input.chars();
@@ -60,7 +82,17 @@ mod lex {
                     (Token::Separator(cur), input)
                 }
             }
-            ';' | ',' | '.' => (Token::Separator(cur), chars.as_str()),
+            ';' | ',' => (Token::Separator(cur), chars.as_str()),
+            '.' => {
+                let og_chars = chars.as_str();
+                match chars.next() {
+                    Some('0'..='9') => {
+                        let (number, rest) = consume_number(input);
+                        (Token::Number(number), rest)
+                    }
+                    _ => (Token::Separator(cur), og_chars),
+                }
+            }
             '(' | ')' | '{' | '}' => (Token::Paren(cur), chars.as_str()),
             '<' | '>' => {
                 input = chars.as_str();
@@ -87,7 +119,7 @@ mod lex {
                 }
             }
             '0'..='9' => {
-                let (number, rest) = consume_any(input, |c| (c >= '0' && c <= '9' || c == '.'));
+                let (number, rest) = consume_number(input);
                 (Token::Number(number), rest)
             }
             'a'..='z' | 'A'..='Z' | '_' => {
@@ -106,11 +138,14 @@ mod lex {
                 }
             }
             '-' => {
-                input = chars.as_str();
-                if chars.next() == Some('>') {
-                    (Token::Arrow, chars.as_str())
-                } else {
-                    (Token::Operation(cur), input)
+                let og_chars = chars.as_str();
+                match chars.next() {
+                    Some('>') => (Token::Arrow, chars.as_str()),
+                    Some('0'..='9') | Some('.') => {
+                        let (number, rest) = consume_number(input);
+                        (Token::Number(number), rest)
+                    }
+                    _ => (Token::Operation(cur), og_chars),
                 }
             }
             '+' | '*' | '/' | '%' | '^' => (Token::Operation(cur), chars.as_str()),