move formatEdge to edge/

TODO.md

@@ -1,3 +1,5 @@
+remove `begin end` syntax
+
 # books
 
 反应网编程

src/lang/edge/formatEdge.ts

@@ -0,0 +1,13 @@
+import { Edge } from "../edge"
+import { formatNode } from "../node/formatNode"
+
+export function formatEdge(edge: Edge): string {
+  const first = formatNode(edge.first.node)
+  const second = formatNode(edge.second.node)
+
+  if (edge.first.isPrincipal && edge.second.isPrincipal) {
+    return `(${first})-${edge.first.name}!${edge.second.name}-(${second})`
+  } else {
+    return `(${first})-${edge.first.name} ${edge.second.name}-(${second})`
+  }
+}

src/lang/net/formatNet.ts

@@ -1,19 +1,7 @@
-import { Edge } from "../edge"
-import { formatNode } from "../node/formatNode"
+import { formatEdge } from "../edge/formatEdge"
 import { Net } from "./Net"
 import { allEdges } from "./allEdges"
 
 export function formatNet(net: Net): string {
   return allEdges(net).map(formatEdge).join("\n")
 }
-
-function formatEdge(edge: Edge): string {
-  const first = formatNode(edge.first.node)
-  const second = formatNode(edge.second.node)
-
-  if (edge.first.isPrincipal && edge.second.isPrincipal) {
-    return `(${first})-${edge.first.name}!${edge.second.name}-(${second})`
-  } else {
-    return `(${first})-${edge.first.name} ${edge.second.name}-(${second})`
-  }
-}