Removes variable-unset! from the interpreters as it is not being used (and not a good idea anyways)

Author: codeZeilen

ports-js/scheme.js

@@ -13,7 +13,6 @@ const _quote = Sym('quote');
 const _if = Sym('if');
 const _cond = Sym('cond');
 const _set = Sym('set!');
-const _unset = Sym('variable-unset!');
 const _define = Sym('define');
 const _lambda = Sym('lambda');
 const _begin = Sym('begin');
@@ -102,14 +101,6 @@ export class Env extends Map {
     throw new Error(`Variable ${Symbol.keyFor(key)} not found`);
   }
 
-  unset(variable) {
-    const key = this.keyFor(variable);
-    if (this.has(key)) {
-      this.delete(key);
-    } else {
-      throw new Error(`Variable ${Symbol.keyFor(key)} not found`);
-    }
-  }
 }
 
 // Helper functions
@@ -340,10 +331,6 @@ function evaluate(x, env = globalEnv) {
       const [_, variable, exp] = x;
       env.find(variable).set(variable, evaluate(exp, env));
       return null;
-    } else if (x[0] === _unset) {
-      const [_, variable] = x;
-      env.find(variable).unset(variable);
-      return null;
     } else if (x[0] === _define) {
       const [_, variable, exp] = x;
       env.set(variable, evaluate(exp, env));

ports-py/lispy.py

@@ -20,8 +20,8 @@ def Sym(s, symbol_table={}):
     if s not in symbol_table: symbol_table[s] = Symbol(s)
     return symbol_table[s]
 
-_quote, _if, _cond, _set, _unset, _define, _lambda, _begin, _definemacro, _include, = list(map(Sym, 
-"quote   if   cond   set!  variable-unset!  define   lambda   begin   define-macro   include".split()))
+_quote, _if, _cond, _set, _define, _lambda, _begin, _definemacro, _include, = list(map(Sym, 
+"quote   if   cond   set!  define   lambda   begin   define-macro   include".split()))
 
 _quasiquote, _unquote, _unquotesplicing = list(map(Sym,
 "quasiquote   unquote   unquote-splicing".split()))
@@ -187,18 +187,7 @@ def find(self, var):
                 return self.outer.find(var)
         finally:
             self.lock.release()
-        
-    def unset(self, var):
-        "Unset a variable in the current environment."
-        self.lock.acquire()
-        try:
-            if var in self: 
-                del self[var]
-            else: 
-                raise LookupError(var)
-        finally:
-            self.lock.release()
-        
+                
     def __str__(self) -> str:
         if self.outer is None:
             return "global env"
@@ -312,10 +301,6 @@ def eval(x, env=global_env):
                 (_, var, exp) = x
                 env.find(var)[var] = eval(exp, env)
                 return None
-            elif x[0] is _unset:       # (variable-unset! var)
-                (_, var) = x
-                env.find(var).unset(var)
-                return None
             elif x[0] is _define:    # (define var exp)
                 (_, var, exp) = x
                 env[var] = eval(exp, env)

ports-s/PortsS-Interpreter/PortsScheme.class.st

@@ -80,9 +80,6 @@ PortsScheme >> evalExprs: element in: env [
 					at: x second
 					put: (self evalExprs: x third in: localEnv).
 				^ nil].
-			[#'variable-unset!' = x first] -> [ 
-				(localEnv find: x second) unset: x second.
-				^ nil].
 			[#define = x first] -> [ 
 				localEnv at: x second put: (self evalExprs: x third in: localEnv).
 				^ nil].

ports-s/PortsS-Interpreter/PortsSchemeEnv.class.st

@@ -80,9 +80,3 @@ PortsSchemeEnv >> setBindingsFor: paramOrParams to: arguments [
 				with: arguments
 				collect: [:a :b | a -> b]]).
 ]
-
-{ #category : #accessing }
-PortsSchemeEnv >> unset: aSymbol [
-
-	bindings removeKey: aSymbol
-]

ports/spec.md

@@ -13,7 +13,6 @@ A PorTS language implementation should implement the following special forms:
  - quote
  - cond
  - set!
- - variable-unset!
  - define
  - lambda
  - begin