r - example_test.go

     1  package walk_test
     2  
     3  import (
     4  	"fmt"
     5  
     6  	"vimagination.zapto.org/parser"
     7  	"vimagination.zapto.org/r"
     8  	"vimagination.zapto.org/r/walk"
     9  )
    10  
    11  func Example() {
    12  	src := `a <- "b" - "c"`
    13  	tk := parser.NewStringTokeniser(src)
    14  
    15  	m, _ := r.Parse(&tk)
    16  
    17  	var walkFn walk.Handler
    18  
    19  	walkFn = walk.HandlerFunc(func(t r.Type) error {
    20  		switch t := t.(type) {
    21  		case *r.AdditionExpression:
    22  			if t.AdditionType == r.AdditionSubtract {
    23  				t.AdditionType = r.AdditionAdd
    24  			}
    25  		case *r.SimpleExpression:
    26  			if t.Constant == nil {
    27  				break
    28  			}
    29  
    30  			switch t.Constant.Data {
    31  			case `"b"`:
    32  				t.Constant.Data = `"Hello"`
    33  			case `"c"`:
    34  				t.Constant.Data = `", World"`
    35  			}
    36  		}
    37  
    38  		return walk.Walk(t, walkFn)
    39  	})
    40  
    41  	walk.Walk(m, walkFn)
    42  
    43  	fmt.Printf("%+s", m)
    44  
    45  	// Output:
    46  	// a <- "Hello" + ", World"
    47  }
    48