Merge pull request #22 from JakeStanger/fix/escape-input

fix: unable to escape input in string interpolation

README.md

@@ -14,7 +14,7 @@ small enough you can learn it in minutes. It was born out of the following frust
 ## What Corn Is Not
 
 Corn is not a full programming language and does not try to be. 
-There are no dynamic variables, there is no interpolation and there are no statement blocks.
+There are no dynamic variables, there are no operations and there are no statement blocks.
 
 Likewise, Corn is not a data exchange format. 
 Unlike JSON or YAML or TOML, you cannot serialize code back into Corn. 
@@ -436,6 +436,8 @@ Evaluates to:
 }
 ```
 
+To use a literal dollar, you can escape with `\$`. For example, `\$subject`. 
+
 #### Merging
 
 Somtimes you want to re-use an object or array to compose a larger object/array. 

assets/inputs/string_interpolation.corn

@@ -3,4 +3,5 @@ let {
  $subject = "world"
 } in {
  foo = "$greeting, $subject"
+ bar = "\$escaped"
 }

assets/outputs/json/string_interpolation.json

@@ -1,3 +1,4 @@
 {
+ "bar": "$escaped",
  "foo": "hello, world"
 }

assets/outputs/toml/string_interpolation.toml

@@ -1,2 +1,3 @@
+bar = "$escaped"
 foo = "hello, world"
 

assets/outputs/yaml/string_interpolation.yml

@@ -1,2 +1,3 @@
+bar: $escaped
 foo: hello, world
 

libcorn/src/grammar.pest

@@ -49,7 +49,7 @@ string_val = ${ (input | char)* }
 
 char = {
  !("\"" | "\\") ~ ANY
- | "\\" ~ ("\"" | "\\" | "n" | "r" | "t")
+ | "\\" ~ ("\"" | "\\" | "n" | "r" | "t" | "$")
  | "\\" ~ ("u" ~ ASCII_HEX_DIGIT{4})
 }
 
@@ -73,7 +73,7 @@ float = @{
  ~ (^"e" ~ ("+" | "-")? ~ ASCII_DIGIT+)?
 }
 
-input = ${ "$" ~ (ASCII_ALPHA | "_") ~ (ASCII_ALPHANUMERIC | "_")+ }
+input = ${ !"\\" ~ "$" ~ (ASCII_ALPHA | "_") ~ (ASCII_ALPHANUMERIC | "_")+ }
 
 assignment = { input ~ "=" ~ value }
 

libcorn/src/parser.rs

@@ -142,6 +142,7 @@ impl<'a> CornParser<'a> {
  'r' => '\r',
  't' => '\t',
  '"' => '\"',
+ '$' => '$',
  '\\' => '\\',
  _ => unreachable!(),
  };