Team: LaFuN

[sophiajt]

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You can find this team's project at: https://github.com/langjam/jam0001/tree/main/LaFuN

[mortie]

I wrote a JSON Encode function as a demonstration. Here's the PDF generated by it:

JSON_Encode.pdf

Here's the PDF as images:

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And here's the source code:

Click to see source code

``` \section{Introduction} JSON (JavaScript Object Notation) is a standard data interchange format. It supports the following basic data types: \begin{itemize} \item Number: A real number. It's represented in JSON as a decimal number, with an optional fractional part. \item String: A sequence of Unicode code points. It's represented in JSON by an opening quote $"$, followed by a sequence of characters, followed by a closing quote $"$. Special values, such as quotes, can be escaped with a backslash. \item Boolean: A boolean value. Represented by the text $true$ or $false$. \item Array: A sequence of JSON values. Represented by an opening bracket $[$, followed by a sequence of JSON values separated by a comma $,$, followed by a closing bracket $]$. \item Object: A map of strings to JSON values. Representing by an opening brace $\{$, followed by a sequence of key/value pairs separated by a comma $,$ followed by a closing brace $\}$. A key/value pair is representedy by a string, followed by a colon $:$, followed by a JSON value. \end{itemize} \section{Implementation} The @jsonEncode function implements a basic encoding function. It acts as the entry-point into JSON encoding, and its only responsibility is to delegate to other functions based on the type of the argument. It takes an argument @val, which is the value to encode. A JSON value is represented in memory as an array, where the first value is one of: "number", "string", "boolean", "array" or "object", and the second value is the object to be encoded. \fun{jsonEncode}{val}{ t := val.get(0); v := val.get(1); if t == "number" { return jsonEncodeNumber(v); } else if t == "string" { return jsonEncodeString(v); } else if t == "boolean" { return jsonEncodeBoolean(v); } else if t == "null" { return jsonEncodeNone(v); } else if t == "array" { return jsonEncodeArray(v); } else if t == "object" { return jsonEncodeObject(v); } else { return none; } } \subsection{Encode Number} The @jsonEncodeNumber function has to produce a string which contains the decimal expansion of a real number. \fun{jsonEncodeNumber}{num}{ return num.toString(); } \subsection{Encode String} The @jsonEncodeString function has to produce a string which contains a JSON string literal, with proper escaping of quotes and backslashes. \fun{jsonEncodeString}{str}{ string := '"'; index := 0; while index < str.length { ch := str.at(index); if ch == '\\' { string = string + '\\\\'; } else if ch == '\"' { string = string + '\\"'; } else { string = string + ch; } index = index + 1; } string = string + "\""; return string; } \subsection{Encode Boolean} The @jsonEncodeBoolean function needs to produce a string which contains either $true$ or $false$. \fun{jsonEncodeBoolean}{bool}{ if bool { return "true"; } else { return "false"; } } \subsection{Encode None} The @jsonEncodeNone function needs to produce a string which contains $null$. \fun{jsonEncodeNone}{val}{ return "null"; } \subsection{Encode Array} The @jsonEncodeArray function needs to produce an array of JSON values, which is represented by an opening bracket $[$, followed by comma-separated JSON values, followed by a closing bracket $]$. It uses the @jsonEncode function to do all the heavy lifting of actually encoding the values. \fun{jsonEncodeArray}{arr}{ string := "["; index := 0; while index < arr.data.length { if index != 0 { string = string + ", "; } string = string + jsonEncode(arr.get(index)); index = index + 1; } string = string + "]"; return string; } \subsection{Encode Object} The @jsonEncodeObject function needs to produce a map of string keys to JSON values, which is represented by an opening brace $\{$, followed by comma-separated key/value pairs, followed by a closing brace $\}$. It uses the @jsonEncode function to encode the values, and the @jsonEncodeString function to encode the keys. It also uses the @indent helper function to produce proper indentation. A JSON object is represented in memory of an array of length $2l$, where $l$ is the number of elements in the map. Elements at even indexes are keys, elements at odd indexes are values. \fun{jsonEncodeObject}{map}{ string := "{"; index := 0; while index < map.data.length { if index != 0 { string = string + ", "; } key := map.get(index); val := map.get(index + 1); string = string + jsonEncodeString(key); string = string + ": "; string = string + jsonEncode(val); index = index + 2; } string = string + "}"; return string; } \section{Demonstration} Here's a simple example program which uses @jsonEncode to encode a fairly complicated nested JSON structure. \fun{main}{}{ topLevel := Array(); topLevel.push("exampleString"); topLevel.push(jsonVal("string", "I'm a \"JSON string\"")); topLevel.push("someNumber"); topLevel.push(jsonVal("number", 100.57)); topLevel.push("nothing"); topLevel.push(jsonVal("null", none)); exampleArray := Array(); exampleArray.push(jsonVal("number", 100)); nestedObject := Array(); nestedObject.push("yes"); nestedObject.push(jsonVal("boolean", "true")); nestedObject.push("no"); nestedObject.push(jsonVal("boolean", false)); exampleArray.push(jsonVal("object", nestedObject)); topLevel.push("exampleArray"); topLevel.push(jsonVal("array", exampleArray)); print(jsonEncode(jsonVal("object", topLevel))); } The above code uses the @jsonVal function, which returns a value tagged with the JSON type so that @jsonEncode understands it. Here's the implementation: \fun{jsonVal}{tag, val}{ arr := Array(); arr.push(tag); arr.push(val); return arr; } The output of that code should be: \begin{verbatim} {"exampleString": "I'm a \"JSON string\"", "someNumber": 100.57, "nothing": null, "exampleArray": [100, {"yes": true, "no": false}]} \end{verbatim} ```

This source code can be used to generate either the linked PDF, or to generate JavaScript code which executes and procudes the result shown in the PDF.