Merge pull request #177 from countvajhula/lambda-core-form

Lambda core form

qi-doc/scribblings/forms.scrbl

@@ -100,6 +100,20 @@ The core syntax of the Qi language. These forms may be used in any @tech{flow}.
   ]
 }
 
+@deftogether[(
+  @defform[(lambda expr ...)]
+  @defform[(λ expr ...)]
+)]{
+  Shorthand for @racket[(esc (lambda ...))].
+
+That is, this lambda is a @emph{Qi} form that expands to a use of @emph{Racket}'s lambda form, providing a shorthand for a common way to describe a flow using Racket.
+
+@examples[
+    #:eval eval-for-docs
+    ((☯ (λ (x) (+ 2 x))) 3)
+  ]
+}
+
 @defform[(clos flo)]{
   A @tech{flow} that generates a flow as a value. Any inputs to the @racket[clos] flow are available to @racket[flo] when it is applied to inputs, i.e. it is analogous to a @hyperlink["https://www.gnu.org/software/guile/manual/html_node/Closure.html"]{closure} in Racket.
 

qi-lib/flow/core/private/form-property.rkt

@@ -18,8 +18,7 @@
 
 (provide form-position?
          attach-form-property
-         tag-form-syntax
-         get-form-property)
+         tag-form-syntax)
 
 (require (only-in racket/function
                   curry))
@@ -43,9 +42,6 @@
 (define (attach-form-property stx)
   (syntax-property stx 'nonterminal 'floe))
 
-(define (get-form-property stx)
-  (syntax-property stx 'nonterminal))
-
 ;; This traverses a syntax object and indiscriminately tags every node
 ;; as a form. If this operation were applied to syntax in the real
 ;; compiler, it would of course lead to the incorrect optimizations we

qi-lib/flow/extended/expander.rkt

@@ -182,6 +182,10 @@ core language's use of #%app, etc.).
     clos
     (clos onex:closed-floe)
     (esc ex:racket-expr)
+    (~> ((~literal lambda) e ...)
+        #'(esc (lambda e ...)))
+    (~> ((~literal λ) e ...)
+        #'(lambda e ...))
 
     ;; core form to express deforestable operations
     (#%deforestable name:id info:id e:deforestable-clause ...)

qi-test/tests/flow.rkt

@@ -285,6 +285,11 @@
      (check-equal? ((☯ (esc (first (list + *)))) 3 7)
                    10
                    "normal racket expressions"))
+    (test-suite
+     "lambda escape shortcut"
+     (check-equal? ((☯ (lambda (v) v)) 3) 3)
+     (check-equal? ((☯ (λ (v) v)) 3) 3)
+     (check-equal? ((☯ (λ () 3))) 3))
     (test-suite
      "elementary boolean gates"
      (test-suite