new eval.go

ast/token.go

@@ -17,10 +17,7 @@
 
 package ast
 
-import (
-    "gitlab.com/whom/shs/log"
-    "unicode"
-)
+import "fmt"
 
 type Token_t int
 const (
@@ -35,166 +32,116 @@ type Token struct {
     Next *Token
     Tag Token_t
     Position int
-    Inner interface{}
+    inner interface{}
 }
 
-const string_delims string = "\"'`"
+/* Appends another token to the end of this token list
+ */
+func (t *Token) Append(arg *Token) {
+    if t.Next != nil {
+        t.Next.Append(arg)
+    } else {
+        t.Next = arg
+    }
+}
 
-func Lex(input string) *Token {
-    if len(input) == 0 {
+/* Print function which is better suited for repl.
+ * This one prints the SEXPRs as one would write them.
+ * Does not evaluate tokens.
+ */
+func (t *Token) String() string {
+    switch t.Tag {
+    case STRING:
+        return "\"" + t.inner.(string) + "\""
+
+    case NUMBER, BOOL:
+        return t.inner.(string)
+
+    case LIST:
+        repr := "("
+        if t.inner.(*Token) == nil {
+            return repr + ")"
+        }
+
+        for i := t.inner.(*Token); i != nil; i = i.Next {
+            repr = repr + i.String() + " "
+        }
+        // remove trailing space
+        return repr[:len(repr)-1] + ")"
+
+    case SYMBOL:
+        return "<" + t.inner.(string) + ">"
+    }
+
+    return "[UNKNOWN CELL TYPE]"
+}
+
+/* Returns a list held by a token
+ * returns nil if token holds no list
+ */
+func (t *Token) Expand() *Token {
+    if t.Tag != LIST {
         return nil
     }
 
-    var ret *Token
-    iter := &ret
-    is_str  := false
-    is_list := false
-
-    tokenBuilder := func (pos int, tok string) {
-        if len(tok) == 0 && !is_list && !is_str {
-            return
-        }
-
-        *iter = new(Token)
-        (*iter).Position = pos
-
-        if is_list {
-            (*iter).Inner = Lex(tok)
-            (*iter).Tag = LIST
-            is_list = false
-
-        } else {
-            (*iter).Inner = tok
-            if is_str {
-                (*iter).Tag = STRING
-                is_str = false
-
-            } else if StrIsNumber(tok) {
-                (*iter).Tag = NUMBER
-
-            } else {
-                (*iter).Tag = SYMBOL
-            }
-        }
-
-        iter = &(*iter).Next
-    }
-
-    // returns -1 on unmatched string delim
-    matchStrEnd := func(start int, delim byte) int {
-        for i := start; i < len(input); i++ {
-            if input[i] == delim {
-                return i
-            }
-        }
-
-        return -1
-    }
-
-    // returns -1 on unmatched string delim
-    // returns -2 on unmatched list delim
-    matchListEnd := func(start int) int {
-        depth := 0
-
-        for i := start; i < len(input); i++ {
-            switch input[i] {
-            case '"','\'','`':
-                i = matchStrEnd(i + 1, input[i])
-                if i == -1 {
-                    return -1
-                }
-
-            case '(':
-                depth++
-
-            case ')':
-                if depth == 0 {
-                    return i
-                } else {
-                    depth -= 1
-                }
-            }
-        }
-
-        return -2
-    }
-
-    needs_alloc := false
-    start_pos := 0
-    for i := 0; i < len(input); i++ {
-        switch input[i] {
-        case '(':
-            start_pos = i + 1
-            i = matchListEnd(start_pos)
-            is_list = true
-            needs_alloc = true
-
-        case '"','\'','`':
-            start_pos = i + 1
-            i = matchStrEnd(start_pos, input[i])
-            is_str = true
-            needs_alloc = true
-
-        case ' ':
-            if i == start_pos {
-                start_pos += 1
-                continue
-            }
-
-            needs_alloc = true
-        }
-
-        if needs_alloc {
-            needs_alloc = false
-            if (i < 0) {
-                // TODO: Maybe not overload this.
-                start_pos = i
-                goto error
-            }
-
-            tokenBuilder(start_pos, input[start_pos:i])
-            start_pos = i+1
-        }
-    }
-
-    if start_pos < len(input) {
-        tokenBuilder(start_pos, input[start_pos:])
-    }
-    return ret
-
-error:
-    // TODO: Hook into error module
-    // TODO: Finalize and GC alloced tokens
-    if start_pos == -1 {
-        log.Log(log.ERR,
-                "Unmatched string delimiter in input. discarding.",
-                "lex")
-    } else if start_pos == -2 {
-        log.Log(log.ERR,
-                "Unmatched list delimiter in input. discarding.",
-                "lex")
-    } else {
-        log.Log(log.ERR,
-                "Unknown error in input. discarding.",
-                "lex")
-    }
-
-    return nil
+    return t.inner.(*Token)
 }
 
-func StrIsNumber(arg string) bool {
-    dotCount := 0
-
-    for _, char := range arg {
-        if !unicode.IsDigit(char) {
-            if char == '.' && dotCount == 0 {
-                dotCount++
-            } else {
-                return false
-            }
-        }
+/* Sets inner to a Token value
+ * returns false if parent token is not a list
+ * otherwise returns true
+ */
+func (t *Token) Direct(head *Token) bool {
+    if t.Tag != LIST {
+        return false
     }
 
+    t.inner = head
     return true
 }
 
+/* If token holds an atomic value
+ * (not a symbol or list)
+ * will return its value as a string
+ * else returns ""
+ */
+func (t *Token) Value() string {
+    if t.Tag == LIST {
+        return ""
+    }
+
+    return t.inner.(string)
+}
+
+/* returns an ascii representation of a token
+ */
+func (t *Token) FmtToken() string {
+    suffix := "->"
+    if t.Next == nil {
+        suffix = ""
+    }
+
+    switch t.Tag {
+    case LIST:
+        return fmt.Sprintf("(%s, [List])%s", "LIST", suffix)
+
+    default:
+        return fmt.Sprintf("(%s, %s)%s", GetTagAsStr(t.Tag), t.inner.(string), suffix)
+    }
+}
+
+/* Returns a tag in text
+ */
+func GetTagAsStr(tag Token_t) string {
+    switch tag {
+    case LIST:
+        return "LIST"
+    case STRING:
+        return "STRING"
+    case NUMBER:
+        return "NUMBER"
+    case SYMBOL:
+        return "SYMBOL"
+    }
+    return "UNKNOWN"
+}