Merge pull request #192 from kevanstannard/syntax-lookup-pipe-operator

Add syntax lookup pipe operator

Author: ryyppy

misc_docs/syntax/operators_pipe.mdx

@@ -0,0 +1,77 @@
+---
+id: "pipe"
+keywords: ["pipe", "operator", "function", "argument"]
+name: "->"
+summary: "This is the `pipe` operator."
+category: "operators"
+---
+
+The `->` operator passes a value into the first argument position of a function. Typically it's used to chain multiple function calls together in a "pipeline like" fashion.
+
+### Example
+
+<CodeTab labels={["ReScript", "JS Output"]}>
+
+```res
+let dieRoll = size => {
+  Js.Math.random_int(1, size)
+}
+
+let dieRollMessage = (value, name) => {
+  "Hi " ++ name ++ ", you rolled a " ++ Js.Int.toString(value)
+}
+
+let message = dieRoll(6)->dieRollMessage("Marshall")
+```
+
+```js
+function dieRoll(size) {
+  return Js_math.random_int(1, size);
+}
+
+function dieRollMessage(value, name) {
+  return "Hi " + name + ", you rolled a " + value.toString();
+}
+
+var message = dieRollMessage(Js_math.random_int(1, 6), "Marshall");
+```
+
+</CodeTab>
+
+Which produces a message such as `Hello Marshall, you rolled a 3`.
+
+You can also explicitly define the argument position of a piped value by using the `_` placeholder: 
+
+<CodeTab labels={["ReScript", "JS Output"]}>
+
+```res example
+let logMsg = (user: string, datestr: string, msg: string): unit => {
+  Js.log(`${user}|${datestr}|${msg}`)
+}
+
+let datestr = "01-01-2021"
+let user = "admin"
+
+// Here, we put the result of toUpperCase into the last position
+// denoted with an _
+Js.String2.toUpperCase("example message")->logMsg(user, datestr, _)
+```
+
+```js
+function logMsg(user, datestr, msg) {
+  console.log(user + "|" + datestr + "|" + msg);
+  
+}
+
+var datestr = "01-01-2021";
+
+var user = "admin";
+
+logMsg(user, datestr, "example message".toUpperCase());
+```
+
+</CodeTab>
+
+### References
+
+* [Pipe](/docs/manual/latest/pipe)