nicer reduce example

pkg/yqlib/doc/Reduce.md

@@ -12,16 +12,14 @@ e.g.
 
 On the LHS we are configuring the collection of items that will be reduced `<exp>` as well as what each element will be called `$<name>`. Note that the array has been splatted into its individual elements.
 
-On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection. 
+On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection. Note that within the block expression, `.` will evaluate to the current value of the accumulator. 
-
-Note that within the block expression, `.` will evaluate to the current value of the accumulator. This effectively means that within the `reduce` block you can no longer access data other than elements of the array set as `$<name>`. For simple things, this is probably fine, but often you will need to refer to other data elements.
-
-This can be done by setting a variable using `as` and piping that into the `reduce` operation, or you can simply refer to `$context` which is exactly that, automatically set for you for convenience. See examples below.
 
 ## yq vs jq syntax
 Reduce syntax in `yq` is a little different from `jq` - as `yq` (currently) isn't as sophisticated as `jq` and its only supports infix notation (e.g. a + b, where the operator is in the middle of the two parameters) - where as `jq` uses a mix of infix notation with _prefix_ notation (e.g. `reduce a b` is like writing `+ a b`).
 
-To that end, the reduce operator is called `ireduce` for backwards compatability if a prefix version of `reduce` is ever added.
+To that end, the reduce operator is called `ireduce` for backwards compatability if a `jq` like prefix version of `reduce` is ever added.
+
+
 ## Sum numbers
 Given a sample.yml file of:
 ```yaml
@@ -39,6 +37,25 @@ will output
 20
 ```
 
+## Merge all yaml files together
+Given a sample.yml file of:
+```yaml
+a: cat
+```
+And another sample another.yml file of:
+```yaml
+b: dog
+```
+then
+```bash
+yq eval-all '. as $item ireduce ({}; . * $item )' sample.yml another.yml
+```
+will output
+```yaml
+a: cat
+b: dog
+```
+
 ## Convert an array to an object
 Given a sample.yml file of:
 ```yaml
@@ -57,47 +74,3 @@ Cathy: apples
 Bob: bananas
 ```
 
-## Merge all documents together - using context
-The _$context_ variable set by reduce lets you access the data outside the reduce block.
-
-Given a sample.yml file of:
-```yaml
-a: cat
-```
-And another sample another.yml file of:
-```yaml
-b: dog
-```
-then
-```bash
-yq eval-all 'fileIndex as $item ireduce ({}; . * ($context | select(fileIndex==$item)) )' sample.yml another.yml
-```
-will output
-```yaml
-a: cat
-b: dog
-```
-
-## Merge all documents together - without using context
-`$context` is just a convenient variable that `reduce` sets, you can use your own for more control
-
-Given a sample.yml file of:
-```yaml
-c:
-  a: cat
-```
-And another sample another.yml file of:
-```yaml
-c:
-  b: dog
-```
-then
-```bash
-yq eval-all '.c as $root | fileIndex as $item ireduce ({}; . * ($root | select(fileIndex==$item)) )' sample.yml another.yml
-```
-will output
-```yaml
-a: cat
-b: dog
-```
-

pkg/yqlib/doc/headers/Reduce.md

@@ -12,13 +12,10 @@ e.g.
 
 On the LHS we are configuring the collection of items that will be reduced `<exp>` as well as what each element will be called `$<name>`. Note that the array has been splatted into its individual elements.
 
-On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection. 
+On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection. Note that within the block expression, `.` will evaluate to the current value of the accumulator. 
-
-Note that within the block expression, `.` will evaluate to the current value of the accumulator. This effectively means that within the `reduce` block you can no longer access data other than elements of the array set as `$<name>`. For simple things, this is probably fine, but often you will need to refer to other data elements.
-
-This can be done by setting a variable using `as` and piping that into the `reduce` operation, or you can simply refer to `$context` which is exactly that, automatically set for you for convenience. See examples below.
 
 ## yq vs jq syntax
 Reduce syntax in `yq` is a little different from `jq` - as `yq` (currently) isn't as sophisticated as `jq` and its only supports infix notation (e.g. a + b, where the operator is in the middle of the two parameters) - where as `jq` uses a mix of infix notation with _prefix_ notation (e.g. `reduce a b` is like writing `+ a b`).
 
-To that end, the reduce operator is called `ireduce` for backwards compatability if a prefix version of `reduce` is ever added.
+To that end, the reduce operator is called `ireduce` for backwards compatability if a `jq` like prefix version of `reduce` is ever added.
+

pkg/yqlib/operator_reduce.go

@@ -39,8 +39,6 @@ func reduceOperator(d *dataTreeNavigator, context Context, expressionNode *Expre
 		return Context{}, err
 	}
 
-	accum.SetVariable("context", context.MatchingNodes)
-
 	log.Debugf("with variable %v", variableName)
 
 	blockExp := expressionNode.Rhs.Rhs

pkg/yqlib/operator_reduce_test.go

@@ -14,31 +14,20 @@ var reduceOperatorScenarios = []expressionScenario{
 		},
 	},
 	{
-		description: "Convert an array to an object",
+		description: "Merge all yaml files together",
-		document:    `[{name: Cathy, has: apples},{name: Bob, has: bananas}]`,
-		expression:  `.[] as $item ireduce ({}; .[$item | .name] = ($item | .has) )`,
-		expected: []string{
-			"D0, P[], (!!map)::Cathy: apples\nBob: bananas\n",
-		},
-	},
-	{
-		description:    "Merge all documents together - using context",
-		subdescription: "The _$context_ variable set by reduce lets you access the data outside the reduce block.",
 		document:    `a: cat`,
 		document2:   `b: dog`,
-		expression:     `fi as $item ireduce ({}; . * ($context | select(fileIndex==$item)) )`,
+		expression:  `. as $item ireduce ({}; . * $item )`,
 		expected: []string{
 			"D0, P[], (!!map)::a: cat\nb: dog\n",
 		},
 	},
 	{
-		description:    "Merge all documents together - without using context",
+		description: "Convert an array to an object",
-		subdescription: "`$context` is just a convenient variable that `reduce` sets, you can use your own for more control",
+		document:    `[{name: Cathy, has: apples},{name: Bob, has: bananas}]`,
-		document:       `c: {a: cat}`,
+		expression:  `.[] as $item ireduce ({}; .[$item | .name] = ($item | .has) )`,
-		document2:      `c: {b: dog}`,
-		expression:     `.c as $root | fileIndex as $item ireduce ({}; . * ($root | select(fileIndex==$item)) )`,
 		expected: []string{
-			"D0, P[], (!!map)::{a: cat, b: dog}\n",
+			"D0, P[], (!!map)::Cathy: apples\nBob: bananas\n",
 		},
 	},
 }