Implement optional right-to-left mode with arrow syntax

js/src/Link.js

@@ -77,7 +77,7 @@ export class Link {
   }
 
 
-  format(lessParentheses = false, isCompoundValue = false) {
+  format(lessParentheses = false, isCompoundValue = false, arrowMode = false) {
     // Empty link
     if (this.id === null && (!this.values || this.values.length === 0)) {
       return lessParentheses ? '' : '()';
@@ -94,10 +94,17 @@ export class Link {
     }
 
     // Format values recursively  
-    const valuesStr = this.values.map(v => this.formatValue(v)).join(' ');
+    const valuesStr = this.values.map(v => this.formatValue(v, arrowMode)).join(' ');
 
     // Link with values only (null id)
     if (this.id === null) {
+      // Arrow mode formatting for directional links
+      if (arrowMode && this.values && this.values.length === 2) {
+        const left = this.formatValue(this.values[0], arrowMode);
+        const right = this.formatValue(this.values[1], arrowMode);
+        return `${left} → ${right}`;
+      }
+
       // For lessParentheses mode with simple values, don't wrap the whole thing
       if (lessParentheses) {
         // Check if all values are simple (no nested values)
@@ -121,7 +128,7 @@ export class Link {
     return lessParentheses && !this.needsParentheses(this.id) ? withColon : `(${withColon})`;
   }
 
-  formatValue(value) {
+  formatValue(value, arrowMode = false) {
     if (!value.format) {
       return Link.escapeReference(value.id || '');
     }
@@ -132,7 +139,7 @@ export class Link {
 
     // For compound links from paths, format values with parentheses
     if (isCompoundFromPaths) {
-      return value.format(false, true);
+      return value.format(false, true, arrowMode);
     }
 
     // Simple link with just an ID - don't wrap in parentheses when used as a value
@@ -141,15 +148,15 @@ export class Link {
     }
 
     // Complex value with its own structure - format it normally with parentheses
-    return value.format(false, false);
+    return value.format(false, false, arrowMode);
   }
 
   needsParentheses(str) {
     return str && (str.includes(' ') || str.includes(':') || str.includes('(') || str.includes(')'));
   }
 }
 
-export function formatLinks(links, lessParentheses = false) {
+export function formatLinks(links, lessParentheses = false, arrowMode = false) {
   if (!links || links.length === 0) return '';
-  return links.map(link => link.format(lessParentheses)).join('\n');
+  return links.map(link => link.format(lessParentheses, false, arrowMode)).join('\n');
 }

js/src/grammar.pegjs

@@ -38,10 +38,22 @@ referenceOrLink = l:multiLineAnyLink { return l; } / i:reference { return { id:
 
 anyLink = ml:multiLineAnyLink eol { return ml; } / sl:singleLineAnyLink { return sl; }
 
-multiLineAnyLink = multiLineValueLink / multiLineLink
+multiLineAnyLink = multiLineValueLink / multiLineLink / multiLineArrowLink
+
+// Multiline arrow syntax support
+multiLineArrowLink = "(" _ left:referenceOrLink __ arrow:("←" / "→") __ right:referenceOrLink _ ")" {
+    if (arrow === "←") {
+        // left ← right means right points to left
+        return { values: [right, left] };
+    } else {
+        // left → right means left points to right  
+        return { values: [left, right] };
+    }
+}
 
 singleLineAnyLink = fl:singleLineLink eol { return fl; }
   / vl:singleLineValueLink eol { return vl; }
+  / al:arrowLink eol { return al; }
 
 multiLineValueAndWhitespace = value:referenceOrLink _ { return value; }
 
@@ -51,6 +63,17 @@ singleLineValueAndWhitespace = __ value:referenceOrLink { return value; }
 
 singleLineValues = list:singleLineValueAndWhitespace+ { return list; }
 
+// Arrow syntax support for directional links
+arrowLink = left:referenceOrLink __ arrow:("←" / "→") __ right:referenceOrLink {
+    if (arrow === "←") {
+        // left ← right means right points to left
+        return { values: [right, left] };
+    } else {
+        // left → right means left points to right  
+        return { values: [left, right] };
+    }
+}
+
 singleLineLink = __ id:reference __ ":" v:singleLineValues { return { id: id, values: v }; }
 
 multiLineLink = "(" _ id:reference _ ":" v:multiLineValues _ ")" { return { id: id, values: v }; }
@@ -81,4 +104,4 @@ _ = whiteSpaceSymbol*
 
 whiteSpaceSymbol = [ \t\n\r]
 
-referenceSymbol = [^ \t\n\r(:)]
+referenceSymbol = [^ \t\n\r(:)←→]