initial

parser/parser.go

@@ -0,0 +1,103 @@
+package parser
+
+import (
+  "errors"
+  "strconv"
+  "strings"
+
+  "github.com/hellerve/argos/ast"
+)
+
+func withoutEmpty(input []string) []string {
+    var r []string
+    for _, str := range input {
+        if str != "" {
+            r = append(r, str)
+        }
+    }
+    return r
+}
+
+func tokenize(input string) []string {
+  return withoutEmpty(strings.Split(strings.Replace(strings.Replace(input, "(", " ( ", -1), ")", " ) ", -1), " "))
+}
+
+func parseValue(input []string) (*ast.AST, error, []string) {
+  var res ast.AST
+
+  f, err := strconv.ParseFloat(input[0], 64)
+
+  if err == nil {
+    res = ast.AST{ast.Num, f}
+    return &res, nil, input[1:]
+  }
+
+  if input[0][0] == '"' {
+    var agg []string
+    for {
+      if len(input) == 0 {
+        return nil, errors.New("Unmatched \""), input
+      }
+      token := input[0]
+      input = input[1:]
+      agg = append(agg, token)
+      if token[len(token)-1] == '"' {
+        break
+      }
+    }
+    res = ast.AST{ast.String, strings.Join(agg, " ")}
+    return &res, nil, input
+  }
+
+  res = ast.AST{ast.Symbol, input[0]}
+  return &res, nil, input[1:]
+}
+
+func parseToken(input []string) (*ast.AST, error, []string) {
+  if len(input) == 0 {
+    return nil, errors.New("Unmatched '('"), input
+  }
+
+  if input[0][0] == '\'' {
+    if (input[0] == "'") {
+      input = input[1:]
+    } else {
+      input = append([]string{input[0][1:]}, input[1:]...)
+    }
+    tmp, err, input := parseToken(input)
+
+    if err != nil {
+      return nil, err, input
+    }
+
+    res := ast.AST{ast.List, []ast.AST{ast.AST{ast.Symbol, "quote"}, *tmp}}
+    return &res, nil, input
+  }
+
+  switch input[0] {
+    case "(": {
+      var l []ast.AST
+      input = input[1:]
+      for input[0] != ")" {
+        elem, err, newInput := parseToken(input)
+
+        if err != nil {
+          return nil, err, input
+        }
+
+        l = append(l, *elem)
+        input = newInput
+      }
+      res := ast.AST{ast.List, l}
+      return &res, nil, input[1:]
+    }
+    case ")": {
+      return nil, errors.New("Unmatched ')'"), input
+    }
+  }
+  return parseValue(input)
+}
+
+func Parse(input string) (*ast.AST, error, []string) {
+  return parseToken(tokenize(input))
+}