Add support for C-style for statements (#23)

corpus/statements.txt

@@ -100,6 +100,43 @@ done
       (command (command_name (word)) (simple_expansion (variable_name)))
       (variable_assignment (variable_name) (raw_string)))))
 
+====================================
+C-style for statements
+====================================
+
+for (( c=1; c<=5; c++ ))
+do
+  echo $c
+done
+
+for (( c=1; c<=5; c++ )) {
+	echo $c
+}
+
+for (( ; ; ))
+do
+  echo 'forever'
+done
+
+---
+
+(program
+  (c_style_for_statement
+    (word)
+    (binary_expression (word) (word))
+    (word)
+    (do_group
+      (command (command_name (word)) (simple_expansion (variable_name)))))
+  (c_style_for_statement
+    (word)
+    (binary_expression (word) (word))
+    (word)
+    (compound_statement
+      (command (command_name (word)) (simple_expansion (variable_name)))))
+  (c_style_for_statement
+    (do_group
+      (command (command_name (word)) (raw_string)))))
+
 ====================================
 If statements
 ====================================

grammar.js

@@ -63,6 +63,7 @@ module.exports = grammar({
       $.test_command,
       $.negated_command,
       $.for_statement,
+      $.c_style_for_statement,
       $.while_statement,
       $.if_statement,
       $.case_statement,
@@ -83,6 +84,21 @@ module.exports = grammar({
       $.do_group
     ),
 
+    c_style_for_statement: $ => seq(
+      'for',
+      '((',
+      optional($._expression),
+      $._terminator,
+      optional($._expression),
+      $._terminator,
+      optional($._expression),
+      '))',
+      choice(
+        $.do_group,
+        $.compound_statement
+      )
+    ),
+
     while_statement: $ => seq(
       'while',
       $._terminated_statement,

src/grammar.json

@@ -53,6 +53,10 @@
           "type": "SYMBOL",
           "name": "for_statement"
         },
+        {
+          "type": "SYMBOL",
+          "name": "c_style_for_statement"
+        },
         {
           "type": "SYMBOL",
           "name": "while_statement"
@@ -128,6 +132,80 @@
         }
       ]
     },
+    "c_style_for_statement": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "for"
+        },
+        {
+          "type": "STRING",
+          "value": "(("
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "_expression"
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_terminator"
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "_expression"
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_terminator"
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "_expression"
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "STRING",
+          "value": "))"
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "do_group"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "compound_statement"
+            }
+          ]
+        }
+      ]
+    },
     "while_statement": {
       "type": "SEQ",
       "members": [