Nothing special here (yet)

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_future/ipel/README.md

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+# Iris Path Expression Language (_future)
+
+
+## Ideas & Goals 
+
+- Optional.
+- No Breaking Changes.
+- No performance cost if not used.
+- Can convert a path for the existing routers, if no router is being used, then it will use its own, new, router.
+- 4+1 basic parameter types: `int`, `string`, `alphabetical`, `path`, (wildcard), `any` based on regexp.
+- Each type has unlimited functions of its own, they should be able to be overriden.
+- Give devs the ability to parse their function's arguments before use them and return a func which is the validator.
+- Function will be a generic type(`interface{}`) in order to devs be able to use any type without boilerplate code for conversions,
+can be done using reflection and reflect.Call, on .Boot time to parse the function automatically, and keep the returning validator function (already tested and worked).
+- The `any` will be the default if dev use functions to the named path parameter but missing a type.
+- If a type doesnt't contains a function of its own, then it will use the `any`'s, so `any` will contain global-use functions too. 
+
+## Preview
+
+`/api/users/{id:int min(1)}/posts`
+
+```go
+minValidator := func(min int) func(string) bool {
+    return func(paramValue string) bool {
+       	paramValueInt, err := strconv.Atoi(paramValue)
+		if err != nil {
+			return false
+		}
+        if paramValueInt < min {
+            return false
+        }
+        return true
+    }
+}
+
+app := iris.New()
+app.Int.Set("min", minValidator)
+```
+
+`/api/{version:string len(2) isVersion()}`
+
+```go
+isVersionStrValidator := func() func(string) bool {
+    versions := []string("v1","v2")
+    return func(paramValue string) bool {
+        for _, s := range versions {
+            if s == paramValue {
+                return true
+            }
+        }
+        return false
+    }
+}
+
+lenStrValidator := func(i int) func(string) bool {
+    if i <= 0 {
+        i = 1
+    }
+    return func(paramValue string) bool {
+       return len(paramValue) != i
+    }
+}
+
+
+app := iris.New()
+app.String.Set("isVersion", isVersionStrValidator)
+app.String.Set("len", lenStrValidator)
+```
+
+`/uploads/{filepath:tail contains(.) else 403}`
+
+```go
+[...]
+
+[...]
+```
+
+`/api/validate/year/{year:int range(1970,2017) else 500}`
+
+```go
+[...]
+
+[...]
+```
+
+## Resources
+- [Lexical analysis](https://en.wikipedia.org/wiki/Lexical_analysis) **necessary**
+- [Top-down parsing](https://en.wikipedia.org/wiki/Top-down_parsing) **necessary**
+- [Recursive descent parser](https://en.wikipedia.org/wiki/Recursive_descent_parser) **basic, continue to the rest after**
+- [Handwritten Parsers & Lexers in Go](https://blog.gopheracademy.com/advent-2014/parsers-lexers/) **very good**
+- [Creating a VM / Compiler Episode 1: Bytecode VM](https://www.youtube.com/watch?v=DUNkdl0Jhgs) **nice to watch**
+- [So you want to write an interpreter?](https://www.youtube.com/watch?v=LCslqgM48D4) **watch it, continue to the rest later on**
+- [Writing a Lexer and Parser in Go - Part 1](http://adampresley.github.io/2015/04/12/writing-a-lexer-and-parser-in-go-part-1.html) **a different approach using the strategy pattern, not for production use in my opinion**
+- [Writing a Lexer and Parser in Go - Part 2](http://adampresley.github.io/2015/05/12/writing-a-lexer-and-parser-in-go-part-2.html)
+- [Writing a Lexer and Parser in Go - Part 3](http://adampresley.github.io/2015/06/01/writing-a-lexer-and-parser-in-go-part-3.html)
+- [Writing An Interpreter In Go](https://www.amazon.com/Writing-Interpreter-Go-Thorsten-Ball/dp/300055808X) **I recommend this book: suitable for both experienced and novice developers**
+
+
+<!-- author's notes:
+
+When finish, I should write an article for new Gophers,  based on all of that I have read the last months on this subject.
+It will help a lot new developers looking for these things.
+
+Also, don't push commits to the _future folder for each change, commit every 2-3 days is enough.
+
+-->