More complex parenthesization system (for cleaner TeX)

casio/texify.rkt

@@ -20,46 +20,62 @@
    [else (error "Unknown syntax entry" conv)]))
 
 (define-table texify-operators
-  [+        "~a + ~a" #t]
-  [-        '(#f "-~a" "~a - ~a") #t]
-  [*        "~a \\cdot ~a" #t]
-  [/        '(#f "\\frac1{~a}" "\\frac{~a}{~a}") #f]
-  [abs      "|~a|" #f]
-  [sqrt     "\\sqrt{~a}" #f]
-  [sqr      "{~a}^2" #t]
-  [exp      "e^{~a}" #f]
-  [expt     "{~a}^{~a}" #t]
-  [log      "\\log ~a " #t]
-  [sin      "\\sin ~a" #t]
-  [cos      "\\cos ~a" #t]
-  [tan      "\\tan ~a" #t]
-  [cotan    "\\cot ~a" #t]
-  [asin     "\\sin^{-1} ~a" #t]
-  [acos     "\\cos^{-1} ~a" #t]
-  [atan     "\\tan^{-1} ~a" #t]
-  [sinh     "\\sinh ~a" #t]
-  [cosh     "\\cosh ~a" #t]
-  [tanh     "\\tanh ~a" #t]
-  [atan2    "\\tan^{-1}_* \frac{~a}{~a}" #f]
-  [if       "~a ? ~a : ~a" #t]
-  [>        "~a > ~a" #t]
-  [<        "~a < ~a" #t]
-  [<=       "~a \\le ~a" #t]
-  [>=       "~a \\ge ~a" #t]
-  [and      "~a \\wedge ~a" #t]
-  [or       "~a \\vee ~a" #t]
-  [mod      "~a \\modb ~a" #t])
+  [+        "~a + ~a" '+ '+]
+  [-        '(#f "-~a" "~a - ~a") '+ '+]
+  [*        "~a \\cdot ~a" '* '*]
+  [/        '(#f "\\frac1{~a}" "\\frac{~a}{~a}") #f #t]
+  [abs      "\\left|~a\\right|" #f #t]
+  [sqrt     "\\sqrt{~a}" #f #t]
+  [sqr      "{~a}^2" #f #f]
+  [exp      "e^{~a}" #f #t]
+  [expt     "{~a}^{~a}" #f #f]
+  [log      "\\log ~a" 'fn #t]
+  [sin      "\\sin ~a" 'fn #t]
+  [cos      "\\cos ~a" 'fn #t]
+  [tan      "\\tan ~a" 'fn #t]
+  [cotan    "\\cot ~a" 'fn #t]
+  [asin     "\\sin^{-1} ~a" 'fn #t]
+  [acos     "\\cos^{-1} ~a" 'fn #t]
+  [atan     "\\tan^{-1} ~a" 'fn #t]
+  [sinh     "\\sinh ~a" 'fn #t]
+  [cosh     "\\cosh ~a" 'fn #t]
+  [tanh     "\\tanh ~a" 'fn #t]
+  [atan2    "\\tan^{-1}_* \frac{~a}{~a}" 'fn #t]
+  [if       "~a ? ~a : ~a" #t #t]
+  [>        "~a > ~a" #f #t]
+  [<        "~a < ~a" #f #t]
+  [<=       "~a \\le ~a" #f #t]
+  [>=       "~a \\ge ~a" #f #t]
+  [and      "~a \\wedge ~a" '* '*]
+  [or       "~a \\vee ~a" '+ '+]
+  [mod      "~a \\modb ~a" #t #f])
 
-(define (texify-expression expr [parens #f])
+(define parens-precedence
+  '(#t fn + * #f))
+
+(define (parens-< a b)
+  (let loop ([l parens-precedence])
+    (cond
+     [(and (eq? (car l) a) (eq? (car l) b)) #f]
+     [(eq? (car l) a) #t]
+     [(eq? (car l) b) #f]
+     [else (loop (cdr l))])))
+
+(define (texify-expression expr [parens #t])
+  "Compile an expression to TeX code.
+   The TeX is intended to be used in math mode.
+
+   `parens` is one of #f, '+, '"
   (match expr
     [(? real?) (number->string expr)]
     [(? symbol?) (hash-ref texify-constants expr (symbol->string expr))]
     [`(,f ,args ...)
      (let* ([template (list-ref (hash-ref texify-operators f) 0)]
-            [parens* (list-ref (hash-ref texify-operators f) 1)]
+            [self-paren-level (list-ref (hash-ref texify-operators f) 1)]
+            [arg-paren-level (list-ref (hash-ref texify-operators f) 2)]
             [args* (for/list ([arg args])
-                     (texify-expression arg parens*))]
+                     (texify-expression arg arg-paren-level))]
             [result (apply-converter template args*)])
-       (if parens
-           (format "\\left(~a\\right)" result)
-           result))]))
+       (if (parens-< parens self-paren-level)
+           result
+           (format "\\left(~a\\right)" result)))]))