feat(calc): Understand percentages

src/main/frontend/extensions/calc.cljc

@@ -28,6 +28,7 @@
 (defn eval* [env ast]
   (insta/transform
    {:number     (comp edn/read-string #(str/replace % "," ""))
+    :percent    (fn percent [a] (/ a 100.00))
     :scientific edn/read-string
     :negterm    (fn neg [a] (- a))
     :expr       identity

src/main/grammar/calc.bnf

@@ -17,11 +17,12 @@ tan = <#'\s*'> <'tan('> expr <')'> <#'\s*'>
 atan = <#'\s*'> <'atan('> expr <')'> <#'\s*'>
 acos = <#'\s*'> <'acos('> expr <')'> <#'\s*'>
 asin = <#'\s*'> <'asin('> expr <')'> <#'\s*'>
-<posterm> = log | ln | trig | scientific | number | variable | <#'\s*'> <'('> expr <')'> <#'\s*'>
+<posterm> = log | ln | trig | percent | scientific | number | variable | <#'\s*'> <'('> expr <')'> <#'\s*'>
 negterm = <#'\s*'> <'-'> posterm
 <term> = negterm | posterm
 scientific = #'\s*[0-9]+\.?[0-9]*(e|E)-?[0-9]+()\s*'
 number = #'\s*\d+(,\d+)*(\.\d*)?\s*'
+percent = number <'%'> <#'\s*'>
 variable = #'\s*[a-zA-Z]+(\_+[a-zA-Z]+)*\s*'
 toassign = #'\s*[a-zA-Z]+(\_+[a-zA-Z]+)*\s*'
 assignment = toassign <#'\s*'> <'='> <#'\s*'> expr

src/test/frontend/extensions/calc_test.cljc

@@ -27,7 +27,12 @@
       (are [value expr] (= value (run expr))
         -98123      "-98123"
         -1123.0     " -112,3.0 "
-        -22.1124131 "-2,2.1124131")))
+        -22.1124131 "-2,2.1124131"))
+    (testing "even as percentages"
+      (are [value expr] (= value (run expr))
+        0.01          "1%"
+        1.0           " 100.00% "
+        0.00169781231 "0.169781231%")))
   (testing "basic operations work"
     (are [value expr] (= value (run expr))
       1             "1 + 0"
@@ -48,15 +53,19 @@
       -1            " 2 * 3 / 3 / -2"
       #?(:clj 1/2
          :cljs 0.5) " 1 / 2"
-      0.5           " 1/ 2.0"))
+      0.5           " 1/ 2.0"
+      2.0           "2*100%"
+      0.01          "2%/2"
+      500e3         "50% * 1e6"))
   (testing "power"
     (are [value expr] (= value (run expr))
-      1.0   "1 ^ 0"
-      4.0   "2^2 "
-      27.0  " 3^ 3"
-      0.125 " 2^ -3"
-      16.0  "2 ^ 2 ^ 2"
-      256.0 "4.000 ^ 4.0"))
+      1.0    "1 ^ 0"
+      4.0    "2^2 "
+      27.0   " 3^ 3"
+      0.125  " 2^ -3"
+      16.0   "2 ^ 2 ^ 2"
+      256.0  "4.000 ^ 4.0"
+      4096.0 "200% ^ 12"))
   (testing "operator precedence"
     (are [value expr] (= value (run expr))
       1     "1 + 0 * 2"