From 62109f33db483fad110922c01b05763b2a9afe2b Mon Sep 17 00:00:00 2001
From: ben <benjaminlgreenman@gmail.com>
Date: Wed, 9 Mar 2016 00:55:31 -0500
Subject: [PATCH] [math] cleaner

---
 math.rkt           |  90 ++--------------------------------
 private/common.rkt |  63 +++++++++++++++---------
 private/math.rkt   | 119 +++++++++++++++++++++++++++++++++++++++++++++
 test/math-fail.rkt |   1 +
 test/math-pass.rkt |  61 ++++++++++++++++++++++-
 5 files changed, 225 insertions(+), 109 deletions(-)
 create mode 100644 private/math.rkt

diff --git a/math.rkt b/math.rkt
index 633fa54..c4d10a5 100644
--- a/math.rkt
+++ b/math.rkt
@@ -10,91 +10,9 @@
 
   expt:
 
-  ;; --
-  (for-syntax
-    nat/expand
-    int/expand
-    number/expand)
+  define-num: let-num:
 )
 
-(require (for-syntax
-  typed/racket/base
-  (only-in racket/format ~a)
-  (only-in racket/syntax format-id)
-  syntax/id-table
-  syntax/parse
-  trivial/private/common
-))
-
-;; =============================================================================
-
-(begin-for-syntax
-  (define-syntax-class/predicate nat/expand exact-nonnegative-integer?)
-  (define-syntax-class/predicate int/expand integer?)
-  (define-syntax-class/predicate number/expand number?)
-)
-
-(define-syntax make-numeric-operator
-  (syntax-parser
-   [(_ f:id)
-    #:with f: (format-id #'f "~a:" (syntax-e #'f))
-    #'(define-syntax (f: stx)
-        (syntax-parse stx
-         [(g e* (... ...))
-          #:with e+* (for/list ([e (in-list (syntax->list #'(e* (... ...))))])
-                       (expand-expr e))
-          (let ([e++ (reduce/op f (syntax->list #'e+*) #:src stx)])
-            (if (list? e++)
-              (quasisyntax/loc #'g (f #,@e++))
-              (quasisyntax/loc #'g #,e++)))]
-         [g:id
-          (syntax/loc #'g f)]
-         [(g e* (... ...))
-          (syntax/loc #'g (f e* (... ...)))]))]))
-
-(make-numeric-operator +)
-(make-numeric-operator -)
-(make-numeric-operator *)
-(make-numeric-operator /)
-
-(define-syntax (expt: stx)
-  (syntax-parse stx
-   [(_ n1:number/expand n2:number/expand)
-    #:with n (expt (syntax-e #'n1.expanded) (syntax-e #'n2.expanded))
-    (syntax/loc stx 'n)]
-   [_:id
-    (syntax/loc stx expt)]
-   [(_ e* ...)
-    (syntax/loc stx (expt e* ...))]))
-
-;; -----------------------------------------------------------------------------
-
-(define-for-syntax (division-by-zero stx)
-  (raise-syntax-error '/ "division by zero" stx))
-
-;; Simplify a list of expressions using an associative binary operator.
-;; Return either:
-;; - A numeric value
-;; - A list of syntax objects, to be spliced back in the source code
-(define-for-syntax (reduce/op op expr* #:src stx)
-  (let loop ([prev #f]      ;; (U #f Number), candidate for reduction
-             [acc  '()]     ;; (Listof Syntax), irreducible arguments
-             [e*   expr*])  ;; (Listof Syntax), arguments to process
-    (if (null? e*)
-      ;; then: finished, return a number (prev) or list of expressions (acc)
-      (if (null? acc)
-        prev
-        (reverse (if prev (cons prev acc) acc)))
-      ;; else: pop the next argument from e*, fold if it's a constant
-      (let ([v (quoted-stx-value? (car e*))])
-        (if (number? v)
-          ;; then: reduce the number
-          (if prev
-            ;; Watch for division-by-zero
-            (if (and (zero? v) (eq? / op))
-              (division-by-zero stx)
-              (loop (op prev v) acc (cdr e*)))
-            (loop v acc (cdr e*)))
-          ;; else: save value in acc
-          (let ([acc+ (cons (car e*) (if prev (cons prev acc) acc))])
-            (loop #f acc+ (cdr e*))))) )))
+(require
+  (only-in trivial/private/math
+    +: -: *: /: expt: let-num: define-num:))
diff --git a/private/common.rkt b/private/common.rkt
index 83bebb2..a59c104 100644
--- a/private/common.rkt
+++ b/private/common.rkt
@@ -11,7 +11,10 @@
   ;; Otherwise, return #f.
 
   define-syntax-class/predicate
-  ;; (stx-> Identifier (-> Any Boolean) SyntaxClassDef)
+  ;; TODO
+
+  lift-predicate
+  ;; TODO
 
   make-value-property
   ;; TODO
@@ -25,7 +28,9 @@
   syntax/parse
   syntax/id-table
   (for-syntax (only-in typed/racket/base let let-syntax #%app))
-  (for-template (only-in typed/racket/base quote)))
+  (for-template
+    (prefix-in r: (only-in racket/base quote))
+    (prefix-in tr: (only-in typed/racket/base quote))))
 
 ;; =============================================================================
 
@@ -34,10 +39,10 @@
    #:attributes (evidence expanded)
    (pattern e
     #:with e+ (expand-expr #'e)
-    #:with p+ (p? #'e+)
-    #:when (if (syntax-e #'p+) #t (begin (printf "ERROR we failed iwth ~a\n" (syntax->datum #'e+)) #f)) ;; TODO remove this
-    #:attr evidence #'p+
-    #:attr expanded #'e+)))
+    #:with p+ (p? (syntax/loc #'e e+))
+    #:when (syntax-e #'p+)
+    #:attr evidence (syntax/loc #'e p+)
+    #:attr expanded (syntax/loc #'e e+))))
 
 (define (expand-expr stx)
   (local-expand stx 'expression '()))
@@ -45,11 +50,20 @@
 (define (quoted-stx-value? stx)
   (and
     (syntax? stx)
-    (syntax-case stx (quote)
-     [(quote v)
+    (syntax-parse stx #:literals (r:quote tr:quote) #:datum-literals (quote)
+     [((~or r:quote tr:quote quote) v)
       (syntax-e #'v)]
      [else #f])))
 
+(define (lift-predicate p?)
+  (lambda (stx)
+    (cond
+     [(p? stx) stx]
+     [(p? (syntax-e stx)) (syntax-e stx)]
+     [(p? (quoted-stx-value? stx))
+      stx]
+     [else #f])))
+
 ;; In:
 ;; - name : Symbol, like format-spec or vector-length or db-schema
 ;; - parser : (Syntax -> Value)
@@ -77,28 +91,28 @@
     (lambda (stx)
       (syntax-parse stx
        [(_ name:id v)
-        #:with v+ (expand-expr #'v)
-        #:when (syntax-e #'v+)
-        #:with m (f-parse #'v+)
-        #:when (syntax-e #'m)
-        (free-id-table-set! #'name (syntax-e #'m))
+        #:with v+ (expand-expr (syntax/loc stx v))
+        #:when (syntax-e (syntax/loc stx v+))
+        #:with m (f-parse (syntax/loc stx v+))
+        #:when (syntax-e (syntax/loc stx m))
+        #:with define-stx (format-id stx "define")
+        (free-id-table-set! tbl #'name (syntax-e #'m))
         (syntax/loc stx
-          (define name v+))]
+          (define-stx name v+))]
        [_ #f])))
   (define f-let
     (lambda (stx)
       (syntax-parse stx
        [(_ ([name*:id v*] ...) e* ...)
-        #:with (v+* ...) (map expand-expr (syntax-e #'(v* ...)))
-        #:when (andmap syntax-e (syntax-e #'(v+* ...)))
-        #:with (m* ...) (map f-parse (syntax-e #'(v+* ...)))
-        #:when (andmap syntax-e (syntax-e #'(m* ...)))
+        #:with (v+* ...) (map expand-expr (syntax-e (syntax/loc stx (v* ...))))
+        #:with (m* ...) (map f-parse (syntax-e (syntax/loc stx (v+* ...))))
+        #:when (andmap syntax-e (syntax-e (syntax/loc stx (m* ...))))
         #:with let-stx (format-id stx "let")
         #:with let-syntax-stx (format-id stx "let-syntax")
         (quasisyntax/loc stx
           (let-stx ([name* v+*] ...)
             (let-syntax-stx ([name* (make-rename-transformer
-                                  (syntax-property #'name* '#,key 'm* ...))] ...)
+                                      (syntax-property #'name* '#,key 'm*))] ...)
               e* ...)))]
        [_ #f])))
   (values
@@ -107,8 +121,13 @@
     f-define
     f-let))
 
-(define ((make-alias id-stx parser) stx)
+(define ((make-alias id-sym parser) stx)
   (or (parser stx)
     (syntax-parse stx
-     [_:id       (quasisyntax/loc stx #,id-stx)]
-     [(_ e* ...) (quasisyntax/loc stx (#,id-stx e* ...))])))
+     [_:id
+      #:with id-stx (format-id stx "~a" id-sym)
+      (syntax/loc stx id-stx)]
+     [(_ e* ...)
+      #:with id-stx (format-id stx "~a" id-sym)
+      #:with app-stx (format-id stx "#%app")
+      (syntax/loc stx (app-stx id-stx e* ...))])))
diff --git a/private/math.rkt b/private/math.rkt
new file mode 100644
index 0000000..b76e10c
--- /dev/null
+++ b/private/math.rkt
@@ -0,0 +1,119 @@
+#lang typed/racket/base
+
+;; Constant-folding math operators.
+;; Where possible, they simplify their arguments.
+
+;; TODO the or- stuff is not so pretty, but it's working anyway
+
+(provide
+  +: -: *: /:
+  ;; Same signature as the racket/base operators,
+  ;;  but try to simplify arguments during expansion.
+
+  expt:
+
+  define-num: let-num:
+
+  ;; --
+  (for-syntax
+    nat/expand
+    int/expand
+    num/expand)
+)
+
+(require (for-syntax
+  typed/racket/base
+  (only-in racket/format ~a)
+  (only-in racket/syntax format-id)
+  syntax/id-table
+  syntax/parse
+  trivial/private/common
+))
+
+;; =============================================================================
+
+(begin-for-syntax
+  (define (division-by-zero stx)
+    (raise-syntax-error '/ "division by zero" stx))
+
+  ;; Simplify a list of expressions using an associative binary operator.
+  ;; Return either:
+  ;; - A numeric value
+  ;; - A list of syntax objects, to be spliced back in the source code
+  (define (reduce/op op stx)
+    (define expr* (syntax-e stx))
+    (cond
+     [(list? expr*)
+      (let loop ([prev #f]      ;; (U #f Number), candidate for reduction
+                 [acc  '()]     ;; (Listof Syntax), irreducible arguments
+                 [e*   expr*])  ;; (Listof Syntax), arguments to process
+        (if (null? e*)
+          ;; then: finished, return a number (prev) or list of expressions (acc)
+          (if (null? acc)
+            prev
+            (reverse (if prev (cons prev acc) acc)))
+          ;; else: pop the next argument from e*, fold if it's a constant
+          (syntax-parse (car e*)
+           [v:num/expand
+            (define v (or (quoted-stx-value? #'v.expanded)
+                          (quoted-stx-value? #'v.evidence)))
+            ;; then: reduce the number
+            (if prev
+              ;; Watch for division-by-zero
+              (if (and (zero? v) (eq? / op))
+                (division-by-zero stx)
+                (loop (op prev v) acc (cdr e*)))
+              (loop v acc (cdr e*)))]
+           [v
+            ;; else: save value in acc
+            (let ([acc+ (cons (car e*) (if prev (cons prev acc) acc))])
+              (loop #f acc+ (cdr e*)))])))]
+     [else  #f]))
+
+  (define-values (nat-key nat? nat-define nat-let)
+    (make-value-property 'number:natural (lift-predicate exact-nonnegative-integer?)))
+  (define-syntax-class/predicate nat/expand nat?)
+
+  (define-values (int-key int? int-define int-let)
+    (make-value-property 'number:integer (lift-predicate integer?)))
+  (define-syntax-class/predicate int/expand int?)
+
+  (define-values (num-key num? num-define num-let)
+    (make-value-property 'number:number (lift-predicate number?)))
+  (define-syntax-class/predicate num/expand num?)
+)
+
+;; -----------------------------------------------------------------------------
+
+(define-syntax define-num: (make-alias 'define num-define))
+(define-syntax let-num: (make-alias 'let num-let))
+
+(define-syntax make-numeric-operator
+  (syntax-parser
+   [(_ f:id)
+    #:with f: (format-id #'f "~a:" (syntax-e #'f))
+    #'(define-syntax f: (make-alias #'f
+        (lambda (stx) (syntax-parse stx
+         [(_ e* (... ...))
+          #:with f-id (format-id stx "~a" 'f)
+          (let ([e+ (reduce/op f #'(e* (... ...)))])
+            (if (list? e+)
+              (quasisyntax/loc stx (#%app f-id #,@e+))
+              (quasisyntax/loc stx #,e+)))]
+         [_ #f]))))]))
+
+(make-numeric-operator +)
+(make-numeric-operator -)
+(make-numeric-operator *)
+(make-numeric-operator /)
+
+(define-syntax expt: (make-alias 'expt
+  (lambda (stx) (syntax-parse stx
+   [(_ n1:num/expand n2:num/expand)
+    (let ([v1 (or (quoted-stx-value? #'n1.expanded)
+                  (quoted-stx-value? #'n1.evidence))]
+          [v2 (or (quoted-stx-value? #'n2.expanded)
+                  (quoted-stx-value? #'n2.evidence))])
+      (and v1 v2 ;; Should never fail
+        (quasisyntax/loc stx #,(expt v1 v2))))]
+   [_ #f]))))
diff --git a/test/math-fail.rkt b/test/math-fail.rkt
index 617c730..332fdc3 100644
--- a/test/math-fail.rkt
+++ b/test/math-fail.rkt
@@ -14,6 +14,7 @@
   (ann (let ([n 5]) (*: n 1/5 1)) One)
   (ann (let ([n 4]) (/: n n)) One)
   (ann (let ([n 2]) (expt: 3 (-: n n))) One)
+  (ann (expt: 3 2) Zero)
   ;; -- lambda => back to racket/base
   (ann ((lambda ([f : (-> Natural Natural Natural)]) (f 0 0)) +:) Zero)
   (ann ((lambda ([f : (-> Natural Natural Integer)]) (f 0 0)) -:) Zero)
diff --git a/test/math-pass.rkt b/test/math-pass.rkt
index 8fa1d91..4df45b8 100644
--- a/test/math-pass.rkt
+++ b/test/math-pass.rkt
@@ -19,6 +19,17 @@
     (ann ((lambda ([f : (-> Integer Integer Integer)]) (f 0 0)) +:) Integer)
     0)
 
+  (check-equal?
+    (let-num: ([n -4] [m 5])
+      (ann (+: m n -1) Zero))
+    0)
+
+  (check-equal?
+    (let ()
+      (define-num: n 6)
+      (define-num: m -8)
+      (ann (+: n 2 m) Zero))
+    0)
 
   ;; -- -:
   (check-equal? (ann (-: 0 0) Zero) 0)
@@ -31,6 +42,17 @@
     (ann ((lambda ([f : (-> Integer Integer Integer)]) (f 0 0)) -:) Integer)
     0)
 
+  (check-equal?
+    (let-num: ([n 4] [m 5])
+      (ann (-: m n 1) Zero))
+    0)
+
+  (check-equal?
+    (let ()
+      (define-num: n 6)
+      (define-num: m -8)
+      (ann (-: n m 14) Zero))
+    0)
 
   ;; -- *:
   (check-equal? (ann (*: 0 1315) Zero) 0)
@@ -43,6 +65,18 @@
     (ann ((lambda ([f : (-> Integer Integer Integer)]) (f 0 0)) *:) Integer)
     0)
 
+  (check-equal?
+    (let-num: ([n 4] [m 5])
+      (ann (-: (*: m n) 20) Zero))
+    0)
+
+  (check-equal?
+    (let ()
+      (define-num: n 2)
+      (define-num: m -8)
+      (ann (-: (*: n -2 m) 32) Zero))
+    0)
+
 
   ;; -- /:
   (check-equal? (ann (/: 0 1) Zero) 0)
@@ -54,6 +88,18 @@
     (ann ((lambda ([f : (-> Integer Integer Exact-Rational)]) (f 1 1)) /:) Real)
     1)
 
+  (check-equal?
+    (let-num: ([n 4] [m 12])
+      (ann (-: (/: m n) 3) Zero))
+    0)
+
+  (check-equal?
+    (let ()
+      (define-num: n 2)
+      (define-num: m -8)
+      (ann (+: (/: m n) 4) Zero))
+    0)
+
 
   ;; -- Nested
   (check-equal?
@@ -90,7 +136,20 @@
     (ann (expt: (+: 5 -5) 78) Zero)
     0)
   (check-equal?
-    (ann (expt: (*: 2 2) (expt: 2 2)) Index)
+    (ann (-: (expt: (*: 2 2) (expt: 2 2)) 256) Zero)
+    0)
+  (check-equal?
+    (ann (expt: (* 2 2) (expt: 2 2)) Natural) ;; Not an index
     256)
+  (check-equal?
+    (let-num: ([n1 5] [n2 4])
+      (ann (-: (expt: n1 n2) 625) Zero))
+    0)
+  (check-equal?
+    (let ()
+      (define-num: n1 8)
+      (define-num: n2 2)
+      (ann (-: (expt: n1 n2) 64) Zero))
+    0)
 
 )