Emmy as JavaScript library (4)

(This post is part of a series, all with the same title) (and needs lots more text to actually explain things)

<script src="https://kloimhardt.github.io/blog/js/emmy.js/build/emmy_bundle.js"></script>

<script>
 var loadEnv = (name) => {
    window[name] = emmy[name];
    return name;
 }
</script>

["div", "mul", "sub", "add", "expt", "sin", "cos"].map(loadEnv);

var _replaceMath = (txt) =>
txt.replace(/\//g,"div")
.replace(/\*/g,"mul")
.replace(/\-/g,"sub")
.replace(/\+/g,"add")
.replace(/\^/g,"expt");

var replaceMath = _replaceMath;

var insertCommas = (txt) =>
txt.replace(/(\w+)/g,'"$1",')
.replace(/\,\s+\]/g," ]");

var makeBrackets = (txt) =>
txt.trim()
.replace(/\(/g,"[ ")
.replace(/\)/g," ],")
.replace(/,$/,"");

var textToJson = (txt) =>
JSON.parse(insertCommas(replaceMath(makeBrackets(txt))));

var _jsonToJs = (j) =>
j.constructor == Array
? jsonToJs(j[0]) + "("  +  j.slice(1).map(jsonToJs) + ")"
: j;

var jsonToJs = _jsonToJs;

var swapFirst = (j) =>
j.constructor == Array
&& ["div", "mul", "sub", "add", "expt"].includes(j[1])
? [j[1], j[0]].concat(j.slice(2)).map(swapFirst)
: j.constructor == Array
? j.map(swapFirst)
: j;

var _expressionToJs = (expr) =>
expr[expr.length-1] === " "
? jsonToJs(swapFirst(textToJson(expr))) + ".toString();"
: "'add blank'";

var expressionToJs = _expressionToJs; null;
    

<script>
     var oldEval = window.eval;
     var newEval = (txt) =>
         txt[0] === "("
         ? oldEval(expressionToJs(txt))
         : oldEval(txt);
     window.eval = newEval;
</script>

((cos (sin 0)) + (((2 / 3) - 4) * (5 ^ 2))) 
   

As a reminder, we can also write the prefix notation

(+ (cos (sin 0)) (* (- (/ 2 3) 4) (expt 5 2))) 
    

(3 * (cos 0)) 
    

((3 * cos) 0) 
    

var symbol = emmy.symbol;

cos(symbol("x")).toString();
    

var replaceMath = (txt) =>
_replaceMath(txt).replace(/\'(\w+)/g,"symbol_$1");

var jsonToJs = (j) =>
j.constructor == String && j.substring(0, 7) == "symbol_"
? 'symbol("' + j.substring(7, j.length) + '")'
: _jsonToJs(j);
    

(cos 'x) 
    

loadEnv("to_infix");

var _preAmble = (j) => ["to_infix", j];
var preAmble = _preAmble;

var _modifyJson = (j) => preAmble(swapFirst(j));
var modifyJson = _modifyJson;

var expressionToJs = (expr) => // new
expr[expr.length-1] === " "
? jsonToJs(modifyJson(textToJson(expr)))
: _expressionToJs(expr);
    

(cos 'x) 
    

((3 * (sin ^ 2)) 'x) 
    

A nice example, click for visual version in clj-tiles

loadEnv("up");
    

(up (* 'R (cos 'phi))
    (* 'R (sin 'phi))) 
    

var drv = emmy.D;
var f = mul(3, expt(sin, 2));
var x = symbol("x");
drv(f)(x).toString();
    

var replaceD = (j) =>
j.constructor == Array
? j.map(replaceD)
: j == "D" ? "drv" : j;

var modifyJson = (j) => _modifyJson(replaceD(j));
    

((D (3 * (sin ^ 2))) 'x) 
    

loadEnv("simplify");

var preAmble = (j) => _preAmble(["simplify", j]);
    

((D (3 * (sin ^ 2))) 'x) 
    

Of course, prefix as well

((D (* 3 (expt sin 2))) 'x)