refactored ast tables, added eval method

ast/eval.go

@@ -0,0 +1,70 @@
+/*   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
+
+type Tree *Token
+
+func (Tree t) Eval(FuncTable funcs, VarTable vars) Tree {
+    if t == nil {
+        return
+    }
+
+    var iter *Token
+    eligibleForSystemCall := true
+
+    reduce := func(Tree t_) Tree {
+        if t_.Next != nil {
+            t_.Next = reduce(t_.Next)
+        }
+
+        switch (t_.Tag) {
+        case SYMBOL:
+            maybeToken := GetVar(t_.Inner, vars)
+            if maybeToken != nil {
+                tok := maybeToken.Eval(funcs, vars)
+                if tok == LIST {
+                    eligibleForSystemCall = false
+                }
+            }
+
+        case LIST:
+            eligibleForSystemCall = false
+            t.Inner = Eval(t_.Inner)
+        }
+
+        return t_
+    }
+
+    ret := reduce(t)
+    if ret.Tag == SYMBOL {
+        f := funcs.GetFunction(ret.Inner)
+        if f == nil {
+            if !eligibleForSystemCall {
+                // TODO: log error
+                return nil
+            }
+
+            // hook into stdlib exec
+            return
+        }
+
+        return (*f).CallFunction(ret.Next)
+    }
+
+    return ret
+}

ast/func_table.go

@@ -21,22 +21,18 @@ import (
     "git.callpipe.com/aidan/shs/ast"
 )
 
-type Operation func(*ast.Token) *ast.Token
+type Operation func(*Token) *Token
 
 type Function struct {
-    function Operation
+    function    Operation
     timesCalled int
-    args   int
+    args        int // TODO: Make this a list of expected types (TAGs)
 }
 
 type FuncTable map[string]*Function
 
-var (
-    GlobalFuncTable *FuncTable
-)
-
 // TODO: Currently only checks arg list length
-func ParseFunction(target *Function, args *ast.Token) bool {
+func (Function f) ParseFunction(args *ast.Token) bool {
     // HANDLE EXEC
     if target.args < 0 {
         return true
@@ -48,27 +44,26 @@ func ParseFunction(target *Function, args *ast.Token) bool {
     }
 
     if i != 0 {
-        // log error here?
+        // TODO: log error here
         return false
     }
 
     return true
 }
 
-func CallFunction(target *Function, args *ast.Token) *ast.Token {
-    if !ParseFunction(target, args) {
-        return args
+func (Function f) CallFunction(args *Token) *Token {
+    if !ParseFunction(f, args) {
+        return nil
     }
 
-    target.timesCalled += 1
-    return target.function(args)
+    f.timesCalled += 1
+    return f.function(args)
 }
 
-func GetFunction(arg string) *Function {
-    target, ok := (*GlobalFuncTable)[arg]
+func (FuncTable table) GetFunction(arg string) *Function {
+    target, ok := table[arg]
     if !ok {
-        // TODO: hook into stdlib exec call
-        ;
+        return nil
     }
 
     return target

ast/token.go

@@ -15,7 +15,7 @@
  *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-package ast;
+package ast
 
 import (
     "unicode"

ast/var_table.go

@@ -19,21 +19,27 @@ package ast
 
 type VarTable map[string]*Token
 
-var (
-    GlobalVarTable *VarTable
-)
+func (VarTable vt) GetVar(arg string) *Token {
+    val, ok := vt[arg]
+    if !ok {
+        return nil
+    }
+
+    return val
+}
 
 // Library represents variables defined in inner scope
 // It is assumed library is ordered from innermost scope to outermost scope
 func GetVar(arg string, library []VarTable) *Token {
-    for scope, dict := range library {
-        val, ok := dict[arg]
-        if ok {
-            scope = scope // TEMP LINE
-            // TODO: maybe log which scope it was found in?
-            return val
+    var res *Token
+    res = nil
+    for i := 0; i < len(library); i += 1 {
+        res = library[i].GetVar(arg)
+        if res != nil {
+            // TODO: Log scope res was found in?
+            break
         }
     }
 
-    return nil
+    return res
 }