Merge pull request #1 from bhmj/memory-optimization-v1

- Zero memory consumption on evaluation (preallocated on parse time)-
- Minor speed optimization
- infinity comparison improved
- invalid hex number detection
- test coverage report added

.vscode/launch.json

@@ -11,7 +11,7 @@
             "mode": "auto",
             "program": "${workspaceFolder}/cmd/xpression/main.go",
             "env": {},
-            "args": ["@.price>10"]
+            "args": ["0xDEFG + 1"]
         }
     ]
 }

Makefile

@@ -12,11 +12,13 @@ help:
 	echo ""
 	echo "  <command> is"
 	echo ""
-	echo "    configure     - install tools and dependencies"
+	echo "    configure     - install tools and dependencies (gocyclo and golangci-lint)"
 	echo "    build         - build jsonslice CLI"
 	echo "    run           - run jsonslice CLI"
 	echo "    lint          - run linters"
 	echo "    test          - run tests"
+	echo "    cover         - generate coverage report"
+	echo ""
 
 configure:
 	go install github.com/fzipp/gocyclo/cmd/gocyclo@latest
@@ -38,6 +40,10 @@ test:
 	go test -cover ./...
 	go test -benchmem -bench=.
 
+cover:
+	go test -coverprofile=coverage.out ./...
+	go tool cover -html=coverage.out
+
 .PHONY: all configure help build run lint test
 
 $(V).SILENT:

README.md

@@ -42,11 +42,12 @@ Expression examples:
 
     // external data in expression (aka variables)
     foobar := 123
-    varFunc := func(name []byte) (*xpression.Operand, error) {
+    varFunc := func(name []byte, result *xpression.Operator) error {
         mapper := map[string]*int{
             `foobar`: &foobar
         }
-        return xpression.Number(float64(*mapper[string(name)])), nil
+        xpression.SetNumber(float64(*mapper[string(name)]))
+        return nil
     }
     tokens, err := xpression.Parse([]byte(`27 / foobar`))
     result, err := xpression.Evaluate(tokens, varFunc)
@@ -81,35 +82,36 @@ Tests cover the majority of cases described in ECMAScript Language definition (s
 
 Evaluate `(2) + (2) == (4)`
 
-```diff
+```golang
 $ go test -bench=. -benchmem -benchtime=4s
 goos: darwin
 goarch: amd64
 pkg: github.com/bhmj/xpression
 cpu: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
-Benchmark_ModifiedNumericLiteral_WithParsing-16        2714204    1853 ns/op    1272 B/op   26 allocs/op
-Benchmark_ModifiedNumericLiteral_WithoutParsing-16    31129712   143.9 ns/op     128 B/op    2 allocs/op
+Benchmark_ModifiedNumericLiteral_WithParsing-16       2622770    1811 ns/op   1272 B/op   26 allocs/op
+Benchmark_ModifiedNumericLiteral_WithoutParsing-16   77455698   57.55 ns/op      0 B/op    0 allocs/op
 PASS
-ok      github.com/bhmj/xpression       12.363s
+ok      github.com/bhmj/xpression       11.548s
 ```
 
 The same expression evaluated with [github.com/Knetic/govaluate](https://github.com/Knetic/govaluate) :
 
-```diff
+```golang
 $ go test -bench='LiteralModifiers' -benchmem -benchtime=4s
 goos: darwin
 goarch: amd64
 pkg: github.com/Knetic/govaluate
 cpu: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
-BenchmarkEvaluationLiteralModifiers_WithParsing-16     1000000    4019 ns/op    2208 B/op    43 allocs/op
-BenchmarkEvaluationLiteralModifiers-16                30173640   147.2 ns/op       8 B/op     1 allocs/op
+BenchmarkEvaluationLiteralModifiers_WithParsing-16    1000000    4019 ns/op   2208 B/op   43 allocs/op
+BenchmarkEvaluationLiteralModifiers-16               30173640   147.2 ns/op      8 B/op    1 allocs/op
 PASS
 ok      github.com/Knetic/govaluate     9.810s
 ```
 
 
 ## Changelog
 
+**0.9.0** (2021-11-19) -- Memory allocation reduced. Speed optimization.  
 **0.8.0** (2021-11-11) -- hex numbers support. Production ready.  
 **0.7.x** (2021-11-11) -- WIP  
 **0.7.0** (2021-11-10) -- project renamed to `xpression`  
@@ -131,7 +133,7 @@ ok      github.com/Knetic/govaluate     9.810s
 - [x] parser test coverage
 - [x] evaluator test coverage
 - [x] add external reference type (node reference in jsonslice)
-- [ ] optimize memory allocations
+- [x] optimize memory allocations
 - [ ] Unicode support!
 
 ## Contributing

cmd/xpression/main.go

@@ -30,11 +30,13 @@ func main() {
 	}
 }
 
-func variableGetter(variable []byte) (*xpression.Operand, error) {
+func variableGetter(variable []byte, result *xpression.Operand) error {
 	if string(variable) == "@.foobar" {
-		return xpression.Number(123), nil
+		result.SetNumber(123)
+		return nil
 	}
-	return xpression.Boolean(false), nil
+	result.SetBoolean(false)
+	return nil
 }
 
 func printParsedExpression(tokens []*xpression.Token) {

errors.go

@@ -7,6 +7,7 @@ var (
 	errUnexpectedEndOfString,
 	errMismatchedParentheses,
 	errNotEnoughArguments,
+	errInvalidHexadecimal,
 	errTooLongHexadecimal error
 )
 
@@ -15,5 +16,6 @@ func init() {
 	errUnexpectedEndOfString = errors.New("unexpected end of string")
 	errMismatchedParentheses = errors.New("mismatched parentheses")
 	errNotEnoughArguments = errors.New("not enough arguments")
+	errInvalidHexadecimal = errors.New("invalid hexadecimal")
 	errTooLongHexadecimal = errors.New("too long hexadecimal")
 }