Add support for != opeartor

Update README

README.md

@@ -4,7 +4,7 @@
 [<img src="https://img.shields.io/badge/try-online%20repl-brightgreen"></img>](https://jetro.io)
 ![GitHub](https://img.shields.io/github/license/mitghi/jetro)
 
-Jetro is a tool for transforming, querying and comparing data in JSON format.
+Jetro is a tool with custom DSL for transforming, querying and comparing data in JSON format.
 
 ```rust
 let data = serde_json::json!({
@@ -34,6 +34,17 @@ let output: Option<Output> = values.from_index(0);
 
 # example
 
+Jetro combines access path with functions which operate on those values matched within the pipeline.
+
+By convention, functions are denoted using # operator. Functions can be composed.
+
+- #pick('string' | expression, ...) [ as | as* 'binding_value' ]
+- #all
+- #sum
+- #formats('format with placeholder {} {}', 'key_a', 'key_b') [ as | as* 'binding_value' ]
+- #filter('target_key' (>, <, >=, <=, ==, ~=) (string, boolean, number))
+
+
 ```json
 {
   "bar": {

src/context.rs

@@ -82,6 +82,7 @@ pub enum FilterOp {
     Lq,
     Gq,
     Eq,
+    NotEq,
     Almost,
 }
 
@@ -111,6 +112,7 @@ impl FilterOp {
             "<" => Some(Self::Less),
             ">" => Some(Self::Gt),
             "~=" => Some(Self::Almost),
+            "!=" => Some(Self::NotEq),
             _ => None,
         }
     }
@@ -304,6 +306,7 @@ macro_rules! do_comparision {
             FilterOp::Gt => $lhs > $rhs,
             FilterOp::Lq => $lhs <= $rhs,
             FilterOp::Gq => $lhs >= $rhs,
+            FilterOp::NotEq => $lhs != $rhs,
             FilterOp::Almost => $lhs.to_lowercase() == $rhs.to_lowercase(),
             _ => false,
         }
@@ -316,6 +319,7 @@ macro_rules! do_comparision {
             FilterOp::Gt => $lhs > $rhs,
             FilterOp::Lq => $lhs <= $rhs,
             FilterOp::Gq => $lhs >= $rhs,
+            FilterOp::NotEq => $lhs != $rhs,
             FilterOp::Almost => {
                 todo!("implement 'almost' operator");
             }

src/fmt.rs

@@ -1,4 +1,5 @@
 //! Module containing string formater for built-in #format function.
+
 use crate::context::FormatOp;
 use dynfmt::{Format, SimpleCurlyFormat};
 use serde_json::Value;

src/grammar.pest

@@ -25,7 +25,8 @@ greater_equal = { ">=" }
 less_equal = { "<=" }
 equal = { "==" }
 almost = { "~=" }
-cmp = { almost | greater_equal | less_equal | equal | greater | less }
+not_euql = { "!=" }
+cmp = { almost | not_euql | greater_equal | less_equal | equal | greater | less }
 true_bool = { "true" }
 false_bool = { "false" }
 truthy = { true_bool | false_bool }

src/parser.rs

@@ -722,4 +722,25 @@ mod test {
             ]
         );
     }
+
+    #[test]
+    fn filter_not_equal() {
+        let actions = parse(">/foo/#filter('some_key' != 10)").unwrap();
+        assert_eq!(
+            actions,
+            vec![
+                Filter::Root,
+                Filter::Child("foo".to_string()),
+                Filter::MultiFilter(Rc::new(RefCell::new(FilterAST {
+                    operand: FilterLogicalOp::None,
+                    left: Some(Rc::new(RefCell::new(FilterInner::Cond {
+                        left: "some_key".to_string(),
+                        op: FilterOp::NotEq,
+                        right: FilterInnerRighthand::Number(10),
+                    }))),
+                    right: None,
+                })))
+            ]
+        );
+    }
 }