From f87458f896ae73796a0f5889d729e9dd5de3a4d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADctor=20L=C3=B3pez=20Ferrando?= <victor@iomob.net>
Date: Tue, 19 Sep 2023 15:53:22 +0200
Subject: [PATCH 1/3] Check that $name is not already on $GLOBAL_BARE_IMPORTS
 before appending

---
 .grit/patterns/importing.md | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/.grit/patterns/importing.md b/.grit/patterns/importing.md
index 4fc9b50..8604196 100644
--- a/.grit/patterns/importing.md
+++ b/.grit/patterns/importing.md
@@ -100,12 +100,14 @@ pattern ensure_import_from($source) {
 
 pattern ensure_imported() {
     $name where {
-      and {
-        $program <: not contains python_import(source=$source) where {
-          $source = $name,
-        },
-        $GLOBAL_BARE_IMPORTS += [$name]
-      }
+        and {
+            $program <: not contains python_import(source=$name),
+            if ($GLOBAL_BARE_IMPORTS <: not some $name) {
+                $GLOBAL_BARE_IMPORTS += [$name]
+            } else {
+                true
+            }
+        }
     }
 }
 

From 621e17f466a05487bb7bd575f80edffc1aac3ca1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADctor=20L=C3=B3pez=20Ferrando?= <victor@iomob.net>
Date: Tue, 19 Sep 2023 16:11:17 +0200
Subject: [PATCH 2/3] Add pattern to replace for loop computing a product to a
 call to math.prod

---
 .grit/patterns/math_prod.md | 101 ++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 .grit/patterns/math_prod.md

diff --git a/.grit/patterns/math_prod.md b/.grit/patterns/math_prod.md
new file mode 100644
index 0000000..620f824
--- /dev/null
+++ b/.grit/patterns/math_prod.md
@@ -0,0 +1,101 @@
+---
+title: Use `math.prod` instead of multiplying in a loop
+---
+
+This pattern transforms a loop that computes the product of a list of numbers into a call to `math.prod` (introduced in Python 3.8).
+
+
+```grit
+engine marzano(0.1)
+language python
+
+pattern prod_init($accum) {
+    or {
+        `$accum = 1`,
+        `$accum = 1.0`,
+    }
+}
+
+pattern prod_accum($accum, $factor) {
+    or {
+        `$accum *= $factor`,
+        `$accum = $accum * $factor`,
+        `$accum = $factor * $accum`,
+    }
+}
+
+`$for` where {
+    $for <: after prod_init(accum = $var) => .,
+    $for <: for_statement(body=block(statements=[prod_accum(accum = $var, factor = $left)]), $left, $right),
+    $left <: identifier(),
+    $import = `math`,
+    $import <: ensure_imported(),
+} => `math.prod($right)`
+```
+
+## Transforms for loop to `math.prod`
+
+
+```python
+n = 1
+for x in range(10):
+    n *= x
+
+n = 1.0
+for x in range(10):
+    n = n * x
+
+n = 1
+for x in range(10):
+    n = x * n
+
+prod = 1
+for x in [4, 5, 6]:
+    prod *= x
+
+# Left as is
+
+n = 1
+for x in range(10):
+    y = n * x
+
+n = 1
+for x in range(10):
+    n = y * x
+
+n = 1
+for x in range(10):
+    n *= x
+    print("multiplied")
+```
+
+```python
+import math
+
+
+math.prod(range(10))
+
+
+math.prod(range(10))
+
+
+math.prod(range(10))
+
+
+math.prod([4, 5, 6])
+
+# Left as is
+
+n = 1
+for x in range(10):
+    y = n * x
+
+n = 1
+for x in range(10):
+    n = y * x
+
+n = 1
+for x in range(10):
+    n *= x
+    print("multiplied")
+```
\ No newline at end of file

From 8399bab951498090f3f38d64d6a71da1340baa8c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADctor=20L=C3=B3pez=20Ferrando?= <victor@iomob.net>
Date: Tue, 19 Sep 2023 16:57:28 +0200
Subject: [PATCH 3/3] Match `for_statement` directly

---
 .grit/patterns/math_prod.md | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/.grit/patterns/math_prod.md b/.grit/patterns/math_prod.md
index 620f824..ad0de19 100644
--- a/.grit/patterns/math_prod.md
+++ b/.grit/patterns/math_prod.md
@@ -24,9 +24,8 @@ pattern prod_accum($accum, $factor) {
     }
 }
 
-`$for` where {
+for_statement(body=block(statements=[prod_accum(accum = $var, factor = $left)]), $left, $right) as $for where {
     $for <: after prod_init(accum = $var) => .,
-    $for <: for_statement(body=block(statements=[prod_accum(accum = $var, factor = $left)]), $left, $right),
     $left <: identifier(),
     $import = `math`,
     $import <: ensure_imported(),