Add comparison operators & ternary operator (#41)

* add comparison operators * add ternary operator * document new features * bump version * wrap condition with '()' * update line in the README related to a ternary op syntax change
rm-hull · Feb 17, 2023 · e36e8aa · e36e8aa
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diff --git a/README.md b/README.md
@@ -196,23 +196,25 @@ referenced in a subsequent function definition:
 
 ### Aliased Operators & Functions
 
-| Alias   | Operator                |     | Alias  | Operator        |     | Alias | Operator        |
-| ------- | ----------------------- | --- | ------ | --------------- | --- | ----- | --------------- |
-| &&      | and                     |     | abs    | Math/abs        |     | sin   | Math/sin        |
-| \|\|    | or                      |     | signum | Math/signum     |     | cos   | Math/cos        |
-| ==      | =                       |     | \*\*   | Math/pow        |     | tan   | Math/tan        |
-| !=      | not=                    |     | exp    | Math/exp        |     | asin  | Math/asin       |
-| %       | mod                     |     | log    | Math/log        |     | acos  | Math/acos       |
-| <<      | bit-shift-left          |     | e      | Math/E          |     | atan  | Math/atan       |
-| >>      | bit-shift-right         |     | π      | Math/PI         |     | sinh  | Math/sinh       |
-| !       | not                     |     | sqrt   | Math/sqrt       |     | cosh  | Math/cosh       |
-| &       | bit-and                 |     | √      | Math/sqrt       |     | tanh  | Math/tanh       |
-| \|      | bit-or                  |     | root   | b √ a           |     | sec   | Secant          |
-|         |                         |     | φ      | Golden ratio    |     | csc   | Cosecant        |
-| gcd     | Greatest common divisor |     | fact   | Factorial       |     | cot   | Cotangent       |
-| lcm     | Least common multiple   |     | ∑      | Sum             |     | asec  | Arcsecant       |
-| rand    | Random number generator |     | ∏      | Product         |     | acsc  | Arccosecant     |
-| randInt | Random int between 0..n |     |        |                 |     | acot  | Arccotangent    |
+| Alias   | Operator                |   | Alias  | Operator     |   | Alias | Operator     |
+|---------|-------------------------|---|--------|--------------|---|-------|--------------|
+| &&      | and                     |   | abs    | Math/abs     |   | sin   | Math/sin     |
+| \|\|    | or                      |   | signum | Math/signum  |   | cos   | Math/cos     |
+| ==      | =                       |   | \*\*   | Math/pow     |   | tan   | Math/tan     |
+| >       | >                       |   | <      | <            |   |       |              |
+| >=      | >=                      |   | <=     | <=           |   |       |              |
+| !=      | not=                    |   | exp    | Math/exp     |   | asin  | Math/asin    |
+| %       | mod                     |   | log    | Math/log     |   | acos  | Math/acos    |
+| <<      | bit-shift-left          |   | e      | Math/E       |   | atan  | Math/atan    |
+| >>      | bit-shift-right         |   | π      | Math/PI      |   | sinh  | Math/sinh    |
+| !       | not                     |   | sqrt   | Math/sqrt    |   | cosh  | Math/cosh    |
+| &       | bit-and                 |   | √      | Math/sqrt    |   | tanh  | Math/tanh    |
+| \|      | bit-or                  |   | root   | b √ a        |   | sec   | Secant       |
+|         |                         |   | φ      | Golden ratio |   | csc   | Cosecant     |
+| gcd     | Greatest common divisor |   | fact   | Factorial    |   | cot   | Cotangent    |
+| lcm     | Least common multiple   |   | ∑      | Sum          |   | asec  | Arcsecant    |
+| rand    | Random number generator |   | ∏      | Product      |   | acsc  | Arccosecant  |
+| randInt | Random int between 0..n |   |        |              |   | acot  | Arccotangent |
 
 ## EBNF Grammar Rules
 
@@ -236,6 +238,8 @@ as follows:
 
 - _**&lt;function&gt;** ::= envref expression | envref "(" &lt;empty&gt; | expression { "," expression } ")"._
 
+- _**&lt;ternary&gt;** ::= "(" expression ")" "?" expression ":" expression._
+
 - _**&lt;envref&gt;** ::= letter { letter | digit | "_" }.\_
 
 - _**&lt;var&gt;** ::= envref._

diff --git a/project.clj b/project.clj
@@ -1,4 +1,4 @@
-(defproject rm-hull/infix "0.4.0"
+(defproject rm-hull/infix "0.4.1"
   :description "A small Clojure library for expressing LISP expressions as infix rather than prefix notation"
   :url "https://github.com/rm-hull/infix"
   :license {

diff --git a/src/infix/core.clj b/src/infix/core.clj
@@ -161,4 +161,8 @@
     :/ /
     :% mod
     :&& logical-and
-    :|| logical-or}))
+    :|| logical-or
+    :> >
+    :< <
+    :>= >=
+    :<= <=}))
diff --git a/src/infix/grammar.clj b/src/infix/grammar.clj
@@ -31,12 +31,13 @@
 ; expression ::= term { addop term }.
 ; term ::= factor { mulop factor }.
 ; factor ::= base { expop base }
-; base ::= "(" expression ")" | boolean | number | var | function.
+; base ::= "(" expression ")" | boolean | number | var | function | ternary.
 ; addop ::= "+" | "-".
 ; mulop ::= "*" | "/".
 ; expop ::= "**"
 ;
 ; function ::= envref expression | envref "(" <empty> | expression { "," expression } ")".
+; ternary ::= expression "?" expression ":" expression.
 ; envref ::= letter { letter | digit | "_" }.
 ; var ::= envref.
 ; boolean :: = "true" | "false"
@@ -147,6 +148,20 @@
                  (f env)
                  (map #(% env) args)))))))
 
+(def ternary-op
+  (m/do*
+   (symb "(")
+   (condition <- expression)
+   (symb ")")
+   (symb "?")
+   (yes-exp <- expression)
+   (symb ":")
+   (no-exp <- expression)
+   (m/return (fn [env]
+               (if (condition env) (yes-exp env) (no-exp env))))
+   )
+  )
+
 (def base
   (any-of
    (m/do*
@@ -157,7 +172,8 @@
    boolean
    number
    var
-   function))
+   function
+   ternary-op))
 
 (defn binary-op [& ops]
   (m/do*
@@ -171,7 +187,7 @@
                   (str (name kw) " is not bound in environment")))))))))
 
 (def expop (binary-op "**"))
-(def mulop (binary-op "*" "/" "÷" "%" ">>" ">>>" "<<" "=" "==" "!="))
+(def mulop (binary-op "*" "/" "÷" "%" ">>" ">>>" "<<" "=" "==" "!=" ">" "<" ">=" "<="))
 (def addop (binary-op "+" "-" "|" "&" "||" "&&"))
 
 (defn- resolve-var [arg env]

diff --git a/test/infix/grammar_test.clj b/test/infix/grammar_test.clj
@@ -116,6 +116,12 @@
     (is (= 43 ((parse-all expression "3 + 5 * 8") env)))
     (is (= 64 ((parse-all expression "(3 + 5) * 8") env)))))
 
+(deftest check-ternary-op
+  (let [env (merge base-env {:t 150 :x 10 :y 20})]
+    (is (= 1 ((parse-all ternary-op "(t > 100) ? 1 : 0") env)))
+    (is (= -10 ((parse-all ternary-op "(t < 100) ? x + y : x - y") env)))
+    (is (= 30 ((parse-all ternary-op "(sum(x, y) >= 30) ? sum(x, y) : 0") env)))))
+
 (deftest check-baseenv-functions
   (is (= 16 ((parse-all expression "9 + 7") base-env)))
   (is (= 12 ((parse-all expression "19 - 7") base-env)))

diff --git a/test/infix/macros_tests.clj b/test/infix/macros_tests.clj
@@ -166,6 +166,14 @@
   (is (true? (infix 5 != 3)))
   (is (true? (infix 5 not= 4))))
 
+(deftest check-comparison
+  (is (true? (infix 3 < 5)))
+  (is (false? (infix 3 > 5)))
+  (is (true? (infix 3 <= 5)))
+  (is (false? (infix 3 >= 5)))
+  (is (true? (infix 3 >= 3)))
+  (is (true? (infix 3 <= 3))))
+
 (deftest check-meta
   (let [hypot (from-string [x y] "sqrt(x**2 + y**2)")
         no-params (from-string "1 + 2")]