{"id":37406,"date":"2018-04-15T03:01:59","date_gmt":"2018-04-14T17:01:59","guid":{"rendered":"http:\/\/www.rjmprogramming.com.au\/ITblog\/?p=37406"},"modified":"2018-04-15T08:26:48","modified_gmt":"2018-04-14T22:26:48","slug":"tcl-and-javascript-and-php-calculator-tutorial","status":"publish","type":"post","link":"https:\/\/www.rjmprogramming.com.au\/ITblog\/tcl-and-javascript-and-php-calculator-tutorial\/","title":{"rendered":"Tcl and Javascript and PHP Calculator Tutorial"},"content":{"rendered":"
\"Tcl<\/a>

Tcl and Javascript and PHP Calculator Tutorial<\/p><\/div>\n

It’s a “blown mind” that has led me to involve Javascript to make the incarnation of our calculator of Tcl and PHP Calculator Tutorial<\/a> allow for some round bracket functionality around the TCL (expr) “kernel” (sorry, Unix … my apologies Linus<\/strike><\/a>Linux)<\/font>. The nexus between what a user may enter, versus the hierarchy needs of TCL’s expr command just blew my mind, man<\/strike>person!<\/p>\n

So what did we turn to? Modernizing<\/a> one’s thinking? We’re onto it? But we digress. Well<\/a>, well.<\/p>\n

We turned to Javascript’s eval<\/a> function, not PHP’s eval<\/a>, nor TCL’s eval<\/a> version, thanks, but no thanks. Nevertheless … and didn’t you just know that “but” would be insulted by the paragraph above?! …<\/font> use of Javascript eval (for round bracketing scenarios or operator hierarchy scenarios) is not the “cakewalk” that you may imagine. That is because …<\/p>\n


\n6 ** 2 \/\/ in TCL \"to the power of\" operator syntax (which remains our web application display choice for the user) has ...
\nMath.pow<\/a>(6, 2) \/\/ Javascript equivalent (behind the scenes)
\n<\/code><\/p>\n

… so we need to cater for that possibility. The Javascript logic is called at the document.body onload<\/i><\/a> event.<\/p>\n

As we often do here<\/a>, the “progression” of logic was to convert some “hardcoded” HTML text (specifically “First Number:” and “:Second Number”) into HTML select (dropdown) elements to the left and to the right (respectively) of the “TCL kernel”, with additional options for the round bracketing the user may want. These dropdowns move out to the edges of the webpage as they make room for user entered additions to the calculation complexity of what they want to calculate. The “Math.pow()” logic needed benefits from the event timing thoughts on the dropdown’s onchange<\/i> event logic, otherwise you’d be doing that dreaded of all dreadeds, in many programmers’ worlds methinks, tracking back through entered “calculator equation” texts to discover when a numerical value becomes an operator, a horrible job when a minus sign can be either, for example. These same “horrible” programming tasks would have been at the fore to making a “TCL only backend solution” come to pass, we are sure, too.<\/p>\n

Can you see from all this how well (clientside) Javascript works with (serverside) PHP? They are a very potent duo, because it is like two bites at the cherry, every time, with their different timings of the application of their logics.<\/p>\n

The downloadable PHP source code calculator.php<\/a> changed this way<\/a> to achieve this extension of functionality still supervising an unchanged calculator.tcl<\/a> TCL source code script, and here is a live run<\/a> link for you to try this calculator for yourself.<\/p>\n

\n

Previous relevant Tcl and PHP Calculator Tutorial<\/a> is shown below.<\/p>\n

\"Tcl<\/a>

Tcl and PHP Calculator Tutorial<\/p><\/div>\n

The Tcl and PHP Primer Tutorial<\/a> was a foretaste to today’s calculator web application that …<\/p>\n