ex src HOF, exceptions, __proto__, return, bind, this and anonymous function

Author: mamouel

HOF avec commentaires/problem1.js

@@ -0,0 +1,194 @@
+function callNoException(f, arg) {
+    try {
+        f(arg);
+        return f(arg);
+    }
+    catch(err) {
+        return null;
+    }
+}
+
+// if f(arg) throws an exception, return null
+// otherwise return what f(arg) returned
+// Example:
+//  function throwsZero(x){
+//     if(x==0) throw new Error("woops");
+//     return x;
+//  }
+//  callNoException(throwsZero, 0) returns null
+//  callNoException(throwsZero, 12) returns 12
+
+//
+// if f(arg) returns null, throw an exception
+    // otherwise return what f(arg) returned  
+    // Example: 
+    //  function nullZero(x) {
+    //     if(x==0) return null;
+    //     return x;
+    //  }
+    // callNoNull(nullZero, 0) throws an exception
+    // callNoNull(nullZero, 12) returns 12
+function callNoNull(f, arg) {
+        var ret = f(arg);
+        if(ret === null) throw new Error("oh no!");
+        return ret
+}
+
+
+
+/* si callNoNull retourne une fonction :
+function callNoNull(f, arg) {
+    function g() {
+        var ret = f(arg);
+        if(ret === null) throw new Error("oh no!");
+        return ret
+    }
+    return g;
+}
+*/
+
+/*
+function callNoNull(f, arg) {
+    if(f(arg) === null) throw "arg is null";
+    return f(arg);
+    }
+    
+function nullZero(x) {
+    if(x==0) return null;
+    return x;
+}
+    
+try {
+    callNoNull(nullZero, 12)
+    } catch(err) {
+    console.log(err)
+}
+*/
+
+//
+function exceptionalize(f) { 
+    return function(arg) {
+        if (f(arg) == null) {throw 'arg is null';}
+        else return f(arg);
+    }
+}
+
+/*function exceptionalize(f) {
+    return f();
+}
+
+function nullZero(x) {
+    if(x==0) return null;
+    return x;
+}
+
+function g(arg) {
+    if(nullZero(arg) === "null") throw "arg is null";
+    return g(arg)
+}
+*/
+
+    // returns a new function
+    // this function takes 1 input, called arg
+    // if f(arg) is null, this new function throws an exception
+    // otherwise it returns what f(arg) returned
+    // difference with callNoNull: callNoNull doesn't return a function
+    // Example: 
+    //  function nullZero(x) {
+    //     if(x==0) return null;
+    //     return x;
+    //  }
+    // exceptionalize(nullZero) returns a function g such that
+    // g(0) throws an exception
+    // g(12) returns 12
+
+
+//
+function nullify(f) {
+    // returns a new function
+    // this function takes 1 input, called arg
+    // if f(arg) throws an exception, this new function returns null
+    // otherwise it returns what f(arg) returned
+    // Example
+    //  function throwsZero(x){
+    //     if(x==0) throw new Error("woops");
+    //     return x;
+    //  }
+    //  nullify(throwsZero) returns a function g such that
+    //  g(0) returns null
+    //  g(12) throws an exception
+    function g(arg) {
+        try {
+            return f(arg);
+        } catch (err) {
+            return null;
+        }
+    }
+    return g;
+}
+
+
+//
+function map(lst, f) {
+    var ret = [];
+    for (index in lst) {
+      ret.push(f(lst[index]));
+    }
+    return ret;
+  }
+  
+  function toUpperCase(str) { return str.toUpperCase(); }
+  map(["bob", "susie"], toUpperCase)
+
+
+  //
+
+  function filter(lst, f) {
+    var arr = [];
+    for(var i = 0; i < lst.length; i++) {
+      if(f(lst[i]) == true) {
+        arr.push(lst[i]);
+      }
+  }
+  return arr;
+}
+
+    // lst is an array and f is a function
+    // f takes one argument and returns a boolean (true or false)
+    // filter(lst, f) returns a list with all the elements of lst that does not satisfy f removed
+    // filter(lst, f) has fewer elements than lst
+    // if lst_ = filter(lst, f) and x is an element of lst_ it means that:
+    //     x is an element of lst
+    //     f(x) is true  
+      
+    // Example:
+    // function isEven(x) {return x % 2 == 0;}
+    // filter([1, 2, 3, 4, 5], isEven) returns [2,4];   
+
+function every(lst, f) {
+    // lst is an array and f is a function
+    // f takes 1 arguments and returns a boolean
+    // filter(lst, f) returns a true if f returns true for every element of lst
+    
+    // Example
+    // every([2,4,12], x => x % 2 == 0) returns true
+    // every([2,3,12], x => x % 2 == 0) returns false 
+    for(var i = 0; i < lst.length; i++) {
+        if(f(lst[i]) === false) {
+            return false;
+        }
+        
+    }  
+    return true;  
+}
+
+
+module.exports = {
+    callNoException, 
+    callNoNull,
+    exceptionalize, 
+    nullify,
+    map, 
+    filter, 
+    every
+};