add stdlib package with readme

ast/print.go

@@ -0,0 +1,110 @@
+/*   SHS: Syntactically Homogeneous Shell
+ *   Copyright (C) 2019  Aidan Hahn
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package ast
+
+import (
+    "strings"
+    "fmt"
+)
+
+/* Print function which is better suited for repl.
+ * This one prints the SEXPRs as one would write them.
+ */
+func (t *Token) String() string {
+    switch t.Tag {
+    case STRING:
+        return "\"" + t.Inner.(string) + "\""
+
+    case NUMBER:
+        return t.Inner.(string)
+
+    case LIST:
+        repr := "("
+        for i := t.Inner.(*Token); i != nil; i = i.Next {
+            repr = repr + i.String() + " "
+        }
+        return repr + ")"
+
+    case SYMBOL:
+        return "<" + t.Inner.(string) + ">"
+    }
+
+    return "[UNKNOWN CELL TYPE]"
+}
+
+/* Print function which breaks each embedded list out on individual lines.
+ * Used in the print_ast debug tool. not too useful for repl applications.
+ * Very useful for debugging syntax though.
+ * TODO: Add numbers to denote embedded scope?
+ */
+func PrintSExprsIndividually(arg *Token) {
+    if arg == nil {
+        return //TODO: Handle error here?
+    }
+
+    var lists TokenStack;
+    lists.Push(arg)
+
+loop:
+    var constructor strings.Builder
+    i := lists.Pop()
+    if i == nil {
+        return
+    }
+
+    for iter := i; iter != nil; iter = iter.Next {
+        if iter.Tag == LIST {
+            lists.Push(iter.Inner.(*Token))
+        }
+
+        constructor.WriteString(FmtToken(iter))
+    }
+
+    println(constructor.String())
+    goto loop
+}
+
+func FmtToken(arg *Token) string {
+    suffix := "->"
+    if arg.Next == nil {
+        suffix = ""
+    }
+
+    switch arg.Tag {
+    case LIST:
+        return fmt.Sprintf("(%s, [List])%s", "LIST", suffix)
+
+    default:
+        return fmt.Sprintf("(%s, %s)%s", GetTagAsStr(arg.Tag), arg.Inner, suffix)
+    }
+}
+
+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"
+}
+