racket only ffmpeg backend. Now no racket-sound-libs are needed anymore.

private/utils.rkt

@@ -21,6 +21,17 @@
            sync-log-sound
            integer->int-bytes
            int-bytes->integer
+
+           let/assert
+           make-assert
+           a-eq? a-!eq?
+           a->? a-<=? a->=? a-<? a-=? a-!=?
+           a-nullptr? a-!nullptr?
+           a-true? a-false?
+           
+           define/return
+           return
+           
            )
 
   (sl-def-log racket-sound sound)
@@ -125,5 +136,103 @@
                 (- u #x1000000)
                 u))
           (integer-bytes->integer bs signed? big? start end))))
+
+  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+  ;; let/assert
+  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+  (define-syntax make-assert
+    (syntax-rules ()
+      ((_ name not-name pred)
+       (begin
+         (define-syntax name
+           (syntax-rules ()
+             ((_ const)
+              (λ (x) (pred x const)))))
+         (define-syntax not-name
+           (syntax-rules ()
+             ((_ const)
+              (λ (x) (not (pred x const))))))
+         )
+       )
+      )
+    )
+
+  (make-assert a-eq? a-!eq? eq?)
+
+  (define a-nullptr? (a-eq? #f))
+  (define a-!nullptr? (a-!eq? #f))
+
+  (make-assert a->? a-<=? >)
+  (make-assert a->=? a-<? >=)
+  (make-assert a-=? a-!=? =)
+
+  (define a-true? (a-eq? #t))
+  (define a-false? (a-eq? #f))
+
+  (struct exn:let/assert exn (value) #:transparent)
+
+  (define (raise-let/assert v)
+    (raise (exn:let/assert "let/assert" (current-continuation-marks) v)))
+
+  (define (let/assert-value r)
+    (exn:let/assert-value r))
+
+  (define-syntax assert-expr
+    (syntax-rules ()
+      ((_ expr cond retval)
+       (let ((a expr)) (if (cond a) a (raise-let/assert retval))))
+      ((_ expr)
+       expr)
+      )
+    )
+
+  (define-syntax let/assert
+    (syntax-rules ()
+      ((_ ((v rest ...) ...) b1 ...)
+       (with-handlers ([exn:let/assert? let/assert-value])
+         (let* ((v (assert-expr rest ...))
+                ...)
+           b1
+           ...
+           )
+         )
+       )
+      )
+    )
+
+  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+  ;; define/return
+  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+  (struct exn:return exn (value) #:transparent)
+
+  (define (raise-return v)
+    (raise (exn:return "return" (current-continuation-marks) v)))
+
+  (define (return-value r)
+    (exn:return-value r))
+  
+  (define-syntax return
+    (syntax-rules ()
+      ((_ val)
+       (raise-return val))))
+
+  (define-syntax define/return
+    (syntax-rules ()
+      ((_ (name ...) b1 ...)
+       (define (name ...)
+         (with-handlers ([exn:return? return-value])
+           b1
+           ...
+           )
+         )
+       )
+      )
+    )
+            
+           
+       
   
 ) ; end of module