From 7ef973af86c070965a4d7c1caf3b13844c4c741b Mon Sep 17 00:00:00 2001
From: Urban Müller
Date: Tue, 6 Jun 2017 15:21:48 +0200
Subject: add filter(), cut(), askey()

---
 it_pipe.class   | 48 ++++++++++++++++++++++++++++++++++++++++--------
 tests/it_pipe.t |  2 ++
 2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/it_pipe.class b/it_pipe.class
index 281ee5f..5ab7e8a 100644
--- a/it_pipe.class
+++ b/it_pipe.class
@@ -84,6 +84,16 @@ function map($expr)
 	return $this;
 }
 
+/**
+ * Apply an expression to every line
+ */
+function filter($expr)
+{
+	$this->lines = it::filter($expr, $this->lines);
+
+	return $this;
+}
+
 /**
  * Convert pipe from utf8 to iso-latin
  */
@@ -101,17 +111,14 @@ function utf8()
 }
 
 /**
- * Return contents of pipe as key->val pair (key must be tab separated)
+ * Select cols from tab-separated cols in each line and tab-joins them again. Key order relevant.
  */
-function keyval()
+function cut($picks)
 {
-	foreach ($this->lines as $line)
-	{
-		list($key, $val) = explode("\t", $line, 2);
-		$result[$key] = $val;
-	}
+	foreach ($this->lines as $idx => $line)
+		$this->lines[$idx] = join("\t", it::filter_keys(explode("\t", $line), $picks, ['reorder' => true]));
 
-	return (array)$result;
+	return $this;
 }
 
 /**
@@ -128,6 +135,31 @@ function swap()
 	return $this;
 }
 
+/**
+ * Return contents of pipe as key->val pair (key must be tab separated).
+ */
+function keyval()
+{
+	foreach ($this->lines as $line)
+	{
+		list($key, $val) = explode("\t", $line, 2);
+		$result[$key] = $val;
+	}
+
+	return (array)$result;
+}
+
+/**
+ * Return contents of pipe as array keys with value true
+ */
+function askey()
+{
+	foreach ($this->lines as $line)
+		$result[$line] = true;
+
+	return (array)$result;
+}
+
 function ED()
 {
 	ED($this->lines);
diff --git a/tests/it_pipe.t b/tests/it_pipe.t
index e8fa4e8..93957b5 100755
--- a/tests/it_pipe.t
+++ b/tests/it_pipe.t
@@ -9,3 +9,5 @@ is(json_encode((new it_pipe(['data' => ["\t", "1\t2"]]))->csv()),        '[{"fie
 is(json_encode((new it_pipe(['data' => ["a\tb", "1\t2"]]))->csv("c,d")), '[{"c":"1","d":"2"}]');
 is(json_encode((new it_pipe(['data' => ["a\tb", "1\t2"]]))->csv(['forceschema' => "c,d"])),  '[{"c":"1","d":"2"}]');
 is(json_encode((new it_pipe(['data' => ["a b\tb", "1\t2"]]))->csv(['fixcolnames' => true])), '[{"a_b":"1","b":"2"}]');
+
+is(json_encode((new it_pipe(['data' => "a\nb\n"]))->askey()), '{"a":true,"b":true}');
-- 
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