Add readme and calc example

calc/calc.go

@@ -0,0 +1,80 @@
+package calc
+
+import (
+	"errors"
+	"fmt"
+
+	. "github.com/vektah/goparsify"
+)
+
+var (
+	value Parser
+
+	sumOp  = Chars("+-", 1, 1)
+	prodOp = Chars("/*", 1, 1)
+
+	groupExpr = Map(And("(", sum, ")"), func(n Node) Node {
+		return Node{Result: n.Child[1].Result}
+	})
+
+	number = Map(NumberLit(), func(n Node) Node {
+		switch i := n.Result.(type) {
+		case int64:
+			return Node{Result: float64(i)}
+		case float64:
+			return Node{Result: i}
+		default:
+			panic(fmt.Errorf("unknown value %#v", i))
+		}
+	})
+
+	sum = Map(And(prod, Kleene(And(sumOp, prod))), func(n Node) Node {
+		i := n.Child[0].Result.(float64)
+
+		for _, op := range n.Child[1].Child {
+			switch op.Child[0].Token {
+			case "+":
+				i += op.Child[1].Result.(float64)
+			case "-":
+				i -= op.Child[1].Result.(float64)
+			}
+		}
+
+		return Node{Result: i}
+	})
+
+	prod = Map(And(&value, Kleene(And(prodOp, &value))), func(n Node) Node {
+		i := n.Child[0].Result.(float64)
+
+		for _, op := range n.Child[1].Child {
+			switch op.Child[0].Token {
+			case "/":
+				i /= op.Child[1].Result.(float64)
+			case "*":
+				i *= op.Child[1].Result.(float64)
+			}
+		}
+
+		return Node{Result: i}
+	})
+
+	Y = Maybe(sum)
+)
+
+func init() {
+	value = Any(number, groupExpr)
+}
+
+func Calc(input string) (float64, error) {
+	result, remaining, err := ParseString(Y, input)
+
+	if err != nil {
+		return 0, err
+	}
+
+	if remaining != "" {
+		return result.(float64), errors.New("left unparsed: " + remaining)
+	}
+
+	return result.(float64), nil
+}

calc/calc_test.go

@@ -0,0 +1,54 @@
+package calc
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNumbers(t *testing.T) {
+	result, err := Calc(`1`)
+	require.NoError(t, err)
+	require.EqualValues(t, 1, result)
+}
+
+func TestAddition(t *testing.T) {
+	result, err := Calc(`1+1`)
+	require.NoError(t, err)
+	require.EqualValues(t, 2, result)
+}
+
+func TestSubtraction(t *testing.T) {
+	result, err := Calc(`1-1`)
+	require.NoError(t, err)
+	require.EqualValues(t, 0, result)
+}
+
+func TestDivision(t *testing.T) {
+	result, err := Calc(`1/2`)
+	require.NoError(t, err)
+	require.EqualValues(t, .5, result)
+}
+
+func TestMultiplication(t *testing.T) {
+	result, err := Calc(`1*2`)
+	require.NoError(t, err)
+	require.EqualValues(t, 2, result)
+}
+
+func TestOrderOfOperations(t *testing.T) {
+	result, err := Calc(`1+10*2`)
+	require.NoError(t, err)
+	require.EqualValues(t, 21, result)
+}
+func TestParenthesis(t *testing.T) {
+	result, err := Calc(`(1+10)*2`)
+	require.NoError(t, err)
+	require.EqualValues(t, 22, result)
+}
+
+func TestRecursive(t *testing.T) {
+	result, err := Calc(`(1+(2*(3-(4/(5)))))`)
+	require.NoError(t, err)
+	require.EqualValues(t, 5.4, result)
+}

combinator.go

@@ -16,10 +16,10 @@ func And(parsers ...Parserish) Parser {
 	parserfied := ParsifyAll(parsers...)
 
 	return NewParser("And()", func(ps *State) Node {
-		result := Node{Children: make([]Node, len(parserfied))}
+		result := Node{Child: make([]Node, len(parserfied))}
 		startpos := ps.Pos
 		for i, parser := range parserfied {
-			result.Children[i] = parser(ps)
+			result.Child[i] = parser(ps)
 			if ps.Errored() {
 				ps.Pos = startpos
 				return result
@@ -90,14 +90,14 @@ func manyImpl(min int, op Parserish, sep ...Parserish) Parser {
 		for {
 			node := opParser(ps)
 			if ps.Errored() {
-				if len(result.Children) < min {
+				if len(result.Child) < min {
 					ps.Pos = startpos
 					return result
 				}
 				ps.ClearError()
 				return result
 			}
-			result.Children = append(result.Children, node)
+			result.Child = append(result.Child, node)
 
 			if sepParser != nil {
 				sepParser(ps)
@@ -153,9 +153,9 @@ func flatten(n Node) string {
 		return n.Token
 	}
 
-	if len(n.Children) > 0 {
+	if len(n.Child) > 0 {
 		sbuf := &bytes.Buffer{}
-		for _, node := range n.Children {
+		for _, node := range n.Child {
 			sbuf.WriteString(flatten(node))
 		}
 		return sbuf.String()

combinator_test.go

@@ -140,7 +140,7 @@ type htmlTag struct {
 
 func TestMap(t *testing.T) {
 	parser := Map(And("<", Chars("a-zA-Z0-9"), ">"), func(n Node) Node {
-		return Node{Result: htmlTag{n.Children[1].Token}}
+		return Node{Result: htmlTag{n.Child[1].Token}}
 	})
 
 	t.Run("sucess", func(t *testing.T) {
@@ -182,7 +182,7 @@ func assertSequence(t *testing.T, node Node, expected ...string) {
 	require.NotNil(t, node)
 	actual := []string{}
 
-	for _, child := range node.Children {
+	for _, child := range node.Child {
 		actual = append(actual, child.Token)
 	}
 

html/html.go

@@ -25,7 +25,7 @@ var (
 	element  = Any(text, &tag)
 	elements = Map(Kleene(element), func(n Node) Node {
 		ret := []interface{}{}
-		for _, child := range n.Children {
+		for _, child := range n.Child {
 			ret = append(ret, child.Result)
 		}
 		return Node{Result: ret}
@@ -35,8 +35,8 @@ var (
 	attrs = Map(Kleene(attr), func(node Node) Node {
 		attr := map[string]string{}
 
-		for _, attrNode := range node.Children {
+		for _, attrNode := range node.Child {
-			attr[attrNode.Children[0].Token] = attrNode.Children[2].Result.(string)
+			attr[attrNode.Child[0].Token] = attrNode.Child[2].Result.(string)
 		}
 
 		return Node{Result: attr}
@@ -48,11 +48,11 @@ var (
 
 func init() {
 	tag = Map(And(tstart, elements, tend), func(node Node) Node {
-		openTag := node.Children[0]
+		openTag := node.Child[0]
 		return Node{Result: Tag{
-			Name:       openTag.Children[1].Token,
+			Name:       openTag.Child[1].Token,
-			Attributes: openTag.Children[2].Result.(map[string]string),
+			Attributes: openTag.Child[2].Result.(map[string]string),
-			Body:       node.Children[1].Result.([]interface{}),
+			Body:       node.Child[1].Result.([]interface{}),
 		}}
 
 	})

json/json.go

@@ -14,7 +14,7 @@ var (
 
 	_array = Map(And("[", Kleene(&_value, ","), "]"), func(n Node) Node {
 		ret := []interface{}{}
-		for _, child := range n.Children[1].Children {
+		for _, child := range n.Child[1].Child {
 			ret = append(ret, child.Result)
 		}
 		return Node{Result: ret}
@@ -23,8 +23,8 @@ var (
 	_object = Map(And("{", _properties, "}"), func(n Node) Node {
 		ret := map[string]interface{}{}
 
-		for _, prop := range n.Children[1].Children {
+		for _, prop := range n.Child[1].Child {
-			ret[prop.Children[0].Result.(string)] = prop.Children[2].Result
+			ret[prop.Child[0].Result.(string)] = prop.Child[2].Result
 		}
 
 		return Node{Result: ret}

json/profile/json.go

@@ -7,6 +7,7 @@ import (
 	"runtime"
 	"runtime/pprof"
 
+	"github.com/vektah/goparsify"
 	"github.com/vektah/goparsify/json"
 )
 
@@ -31,7 +32,7 @@ func main() {
 			}
 		}()
 	}
-	max := 100000
+	max := 1000
 	if *memprofile != "" {
 		runtime.MemProfileRate = 1
 		max = 1000
@@ -52,6 +53,7 @@ func main() {
 			panic(err)
 		}
 	}
+	goparsify.DumpDebugStats()
 }
 
 // This string was taken from http://json.org/example.html

licence.md

@@ -0,0 +1,19 @@
+Copyright (c) 2017 Adam Scarr
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

parser.go

@@ -8,7 +8,7 @@ import (
 
 type Node struct {
 	Token  string
-	Children []Node
+	Child  []Node
 	Result interface{}
 }
 

readme.md

@@ -0,0 +1,151 @@
+goparsify
+=========
+
+A parser-combinator library for building easy to test, read and maintain parsers using functional composition. 
+
+### todo
+ - godoc: I've been slack and the interfaces have been changing rapidly.
+ - fatal errors: Some way for a parser to say "Ive found a good match, the input is broken, stop here with an error"
+ - better errors: currently only the longest error is returned, but it would be nice to show all expected tokens that could follow.
+
+
+### benchmarks
+I dont have many benchmarks set up yet, but the json parser is very promising. Nearly keeping up with the stdlib for raw speed:
+```
+$ go test -bench=. -benchtime=2s -benchmem ./json
+BenchmarkUnmarshalParsec-8         50000             71447 ns/op           50464 B/op       1318 allocs/op
+BenchmarkUnmarshalParsify-8        50000             56414 ns/op           43887 B/op        334 allocs/op
+BenchmarkUnmarshalStdlib-8         50000             50187 ns/op           13949 B/op        262 allocs/op
+PASS
+ok      github.com/vektah/goparsify/json        10.840s
+```
+
+### debugging mode
+If you build the parser with -tags debug it will instrument each parser and a call to DumpDebugStats() will show stats:
+```
+               Any()    415.7136ms           87000      calls  json.go:35
+               Map()    309.6569ms           12000      calls  json.go:31
+               And()    298.6519ms           12000      calls  json.go:23
+            Kleene()    290.6462ms           12000      calls  json.go:13
+               And()    272.6392ms           81000      calls  json.go:13
+               And()     78.0404ms           13000      calls  json.go:15
+               Map()     78.0404ms           13000      calls  json.go:21
+            Kleene()     77.0401ms            1000      calls  json.go:15
+      string literal      7.5053ms           81000      calls  json.go:13
+      string literal      4.5031ms           84000      calls  json.go:11
+                   ,      4.0008ms           81000      calls  json.go:13
+               false      2.0018ms           85000      calls  json.go:10
+                null      2.0005ms           87000      calls  json.go:8
+                true       1.501ms           87000      calls  json.go:9
+                   :       500.8µs           81000      calls  json.go:13
+                   [            0s           13000      calls  json.go:15
+                   }            0s           12000      calls  json.go:23
+                   {            0s           12000      calls  json.go:23
+      number literal            0s           31000      calls  json.go:12
+                   ]            0s            1000      calls  json.go:15
+                 Nil            0s               0      calls  profile/json.go:148
+                   ,            0s            5000      calls  json.go:15
+```
+All times are cumulative, it would be nice to break this down into a parse tree with relative times. This is a nice addition to pprof as it will break down the parsers based on where they are used instead of grouping them all by type. 
+
+This is **free** when the debug tag isnt used.  
+
+### example calculator
+Lets say we wanted to build a calculator that could take an expression and calculate the result.
+
+Lets start with test:
+```go
+func TestNumbers(t *testing.T) {
+	result, err := Calc(`1`)
+	require.NoError(t, err)
+	require.EqualValues(t, 1, result)
+}
+```
+
+Then define a parser for numbers
+```go
+var number = Map(NumberLit(), func(n Node) Node {
+    switch i := n.Result.(type) {
+    case int64:
+        return Node{Result: float64(i)}
+    case float64:
+        return Node{Result: i}
+    default:
+        panic(fmt.Errorf("unknown value %#v", i))
+    }
+})
+
+func Calc(input string) (float64, error) {
+	result, remaining, err := ParseString(number, input)
+
+	if err != nil {
+		return 0, err
+	}
+
+	if remaining != "" {
+		return result.(float64), errors.New("left unparsed: " + remaining)
+	}
+
+	return result.(float64), nil
+}
+```
+
+This parser will return numbers either as float64 or int depending on the literal, for this calculator we only want floats so we Map the results and type cast.
+
+Run the tests and make sure everything is ok.
+
+Time to add addition
+
+```go
+func TestAddition(t *testing.T) {
+	result, err := Calc(`1+1`)
+	require.NoError(t, err)
+	require.EqualValues(t, 2, result)
+}
+
+
+var sumOp  = Chars("+-", 1, 1)
+
+sum = Map(And(number, Kleene(And(sumOp, number))), func(n Node) Node {
+    i := n.Child[0].Result.(float64)
+
+    for _, op := range n.Child[1].Child {
+        switch op.Child[0].Token {
+        case "+":
+            i += op.Child[1].Result.(float64)
+        case "-":
+            i -= op.Child[1].Result.(float64)
+        }
+    }
+
+    return Node{Result: i}
+})
+
+// and update Calc to point to the new root parser -> `result, remaining, err := ParseString(sum, input)`
+```
+
+This parser will match number ([+-] number)+, then map its to be the sum. See how the Child map directly to the positions in the parsers? n is the result of the and, n.Child[0] is its first argument, n.Child[1] is the result of the Kleene parser, n.Child[1].Child[0] is the result of the first And and so fourth. Given how closely tied the parser and the Map are it is good to keep the two together.
+
+You can continue like this and add multiplication and parenthesis fairly easily. Eventually if you keep adding parsers you will end up with a loop, and go will give you a handy error message like:
+```
+typechecking loop involving value = goparsify.Any(number, groupExpr)
+```
+
+we need to break the loop using a pointer, then set its value in init
+```
+var (
+    value Parser
+    prod = And(&value, Kleene(And(prodOp, &value)))
+)
+
+func init() {
+	value = Any(number, groupExpr)
+}
+```
+
+Take a look at [calc](calc/calc.go) for a full example.
+
+
+### prior art
+
+Inspired by https://github.com/prataprc/goparsec but the interfaces have been cleaned up a lot.