guile: Fix crash/exception on literal empty list

Issue #190

guile/step3_env.scm

@@ -58,6 +58,7 @@
        (else (lp (cddr next) (cons (car next) k) (cons (cadr next) v))))))
   (match ast
     ((? (lambda (x) (not (list? x)))) (eval_ast ast env))
+    (() ast)
     (('def! k v) ((env 'set) k (EVAL v env)))
     (('let* kvs body)
      (let* ((new-env (make-Env #:outer env))

guile/step4_if_fn_do.scm

@@ -60,6 +60,7 @@
        ((null? (cdr next)) (throw 'mal-error "let*: Invalid binding form" kvs)) 
        (else (lp (cddr next) (cons (car next) k) (cons (cadr next) v))))))
   (match ast
+    (() ast)
     (('def! k v) ((env 'set) k (EVAL v env)))
     (('let* kvs body)
      (let* ((new-env (make-Env #:outer env))

guile/step5_tco.scm

@@ -68,6 +68,7 @@
   ;;       If you're Lispy enough, there's no recursive at all while you saw named let loop.
   (let tco-loop((ast ast) (env env))
     (match ast
+      (() ast)
       (('def! k v) ((env 'set) k (EVAL v env)))
       (('let* kvs body)
        (let* ((new-env (make-Env #:outer env))

guile/step6_file.scm

@@ -70,6 +70,7 @@
   ;;       If you're Lispy enough, there's no recursive at all while you saw named let loop.
   (let tco-loop((ast ast) (env env))
     (match ast
+      (() ast)
       (('def! k v) ((env 'set) k (EVAL v env)))
       (('let* kvs body)
        (let* ((new-env (make-Env #:outer env))

guile/step7_quote.scm

@@ -84,6 +84,7 @@
   ;;       If you're Lispy enough, there's no recursive at all while you saw named let loop.
   (let tco-loop((ast ast) (env env))
     (match ast
+      (() ast)
       (('quote obj) obj)
       (('quasiquote obj) (EVAL (_quasiquote (->list obj)) env))
       (('def! k v) ((env 'set) k (EVAL v env)))

guile/step8_macros.scm

@@ -54,6 +54,7 @@
 
 (define (is_macro_call ast env)
   (and (list? ast)
+       (> (length ast) 0)
        (and=> (env-check (car ast) env) is-macro?)))
 
 (define (_macroexpand ast env)
@@ -91,6 +92,7 @@
     (let ((ast (_macroexpand ast env)))
       (match ast
         ((? non-list?) (eval_ast ast env))
+        (() ast)
         (('defmacro! k v)
          (let ((c (EVAL v env)))
            (callable-is_macro-set! c #t)

guile/step9_try.scm

@@ -55,6 +55,7 @@
 
 (define (is_macro_call ast env)
   (and (list? ast)
+       (> (length ast) 0)
        (and=> (env-check (car ast) env) is-macro?)))
 
 (define (_macroexpand ast env)
@@ -95,6 +96,7 @@
     (let ((ast (_macroexpand ast env)))
       (match ast
         ((? non-list?) (eval_ast ast env))
+        (() ast)
         (('defmacro! k v)
          (let ((c (EVAL v env)))
            (callable-is_macro-set! c #t)

guile/stepA_mal.scm

@@ -69,6 +69,7 @@
 
 (define (is_macro_call ast env)
   (and (list? ast)
+       (> (length ast) 0)
        (and=> (env-check (car ast) env) is-macro?)))
 
 (define (_macroexpand ast env)
@@ -107,6 +108,7 @@
     (let ((ast (_macroexpand ast env)))
       (match ast
         ((? non-list?) (eval_ast ast env))
+        (() ast)
         (('defmacro! k v)
          (let ((c (EVAL v env)))
            (callable-is_macro-set! c #t)