Learning Curve: Quick, Calculate!

13 Oct, 2005 By: Bill Fane Cadalyst

AutoCAD 2006's new QuickCal palette is easy to find and to use.

Once upon a time, a short time ago, in a Learning Curve column not far away, I covered AutoCAD's geometry calculator function 'Cal. We saw that it is an extremely powerful calculator built into AutoCAD. As well as the routine mathematical and scientific functions, it will also handle a series of vector calculations on AutoCAD points and entities.

The bad news is that 'Cal has two shortcomings. Its operation is a little eclectic ("snarly" comes to mind). The other problem is that it is almost invisible because it does not appear in a single menu or toolbar. The only way to invoke it is to type in the Cal command.

Quick CalculatorThe good news is that AutoCAD 2006 introduced the Quick Calculator. The formal command name is QuickCalc, but don't bother memorizing it. Unlike 'Cal, it turns up everywhere you need it. You will find its icon in the Tools menu, the Standard toolbar and all over the Properties palette. To find it in the latter location, simply click in any window that contains a numeric value, and it appears at the right end of the window.

QuickCalc takes care of the second problem with 'Cal, so let's move back to the first one.

Go Figure!
Click Tools / QuickCalc, or click on its icon in the Standard toolbar, which brings up the palette (figure 1).

Figure 1. The QuickCalc interface is easy to understand.

Hey, this looks remarkably like a standard pocket calculator!

Exactly. Let's look at the number pad first. If you do not see a number pad like figure 1, but instead just see its header bar, then simply click on the double down arrows to expand it.

You can enter numbers and operators by clicking on their buttons in the QuickCalc palette or by typing from the keyboard. Whatever you click or type appears in the input window, which is the single-line window just above the Basic Calculator Mode annotation. You can chain multiple operations together in the input window (figure 2).

Figure 2. You can enter multiple operations into the input window.

When you click on the equals button button or press Enter, the result is evaluated and is posted to the input window. At the same time, the expression and its answer are posted to the larger history window above the input window (figure 3), much like the paper tape in old mechanical adding machines. (Is anyone else out there old enough to remember these?)

Figure 3. Pressing Enter or clicking the equals button button evaluates the expression.

I don't know for sure how long the history tape is because I gave up at 120 entries. You can also grip and drag the lower edge of the history window to change its size.

The result is available for further input, so you could simple enter +10 to get the new answer 19.2285. . .

You may want to repeat a basic calculation but with revised values. No need to re-enter it to the input line; just right-click on any line in the history window, and then click on Append Expression to Input Window in the context menu that appears.

QuickCalc remembers its history list within an editing session. If you close it, do some other drawing work and then invoke it again, the history is still there.

Parentheses can be used to nest expressions. The usual mathematical rules of precedence apply. QuickCalc evaluates expressions within the deepest level of nested parentheses first, and then works its way out.

Next come exponentiation (powers and roots) followed by multiplication and division. Addition and subtraction come last. Operations of equal precedence -- multiply and divide, for example -- are evaluated left to right.

The function of most of the number pad buttons and their keyboard equivalents is obvious from their icons. A few need a quick explanation, however.

clear clears the input window, as does the Esc key.
backspace is the same as the Backspace key.
square root finds the square root of a number. From the keyboard, it is entered as sqrt(n), including the parentheses with no spaces, where n is the number whose square root you want to find. Note that this function, like most others, allows the argument to be a nested series of functions so that sqrt((3+4)/5) is quite legal, and in fact returns 1.1832159566199.

The Three Signs of Old Age
The first is loss of memory,
. . . and I forget the other two.

QuickCalc includes its own internal memory, as controlled by these buttons:
memory store stores the current input-window value into the memory, writing over anything that may already be there. If the input window contains an unevaluated expression, then it is evaluated and the resultant number is stored. The input window will continue to display the full expression.
memory add adds the current input window resultant to anything already in the memory. Interestingly, there is no "memory subtract" function. To subtract from memory, you must add a negative value.
memory recall recalls the current memory value and pastes it into the input window at the current cursor location. It does not need to be at the end of the input expression, but can be anywhere within the window.
memory clear clears the memory.

That pretty much covers the basic calculator functions, so let's forge on and look at some of QuickCalcs's other features.

Notice the toolbar icons across the top of the QuickCalc palette. The one of primary interest right now is the third one from the left. The paste to button will evaluate the current input window expression and paste its result to the Command prompt or to any command that is currently asking for a value. For example, you could start the Circle command, pick a center point, and then calculate a value for the radius.

Another interesting feature is the fact that QuickCal is a palette, so you do not need to invoke it as a command each time. It can simply float on screen, waiting for you to use it any time you need it. As a palette, you can dock it or set it to automatically hide itself until you roll over the left border bar or set its transparency.

If you invoke it from the Properties palette, then a slightly different version comes up. It looks and works almost exactly the same, but now it is labeled Property Calculation rather than Basic Calculator Mode. It does not have the Paste to Command Line button, but instead has an Apply button in the lower left corner. This obviously applies the current result to the property being modified.

Actually, QuickCalc has so many other features that we can't cover them all in one column. Be sure to come back next time when we dig a little deeper into the magic of QuickCalc, including user-defined memory values and custom functions that you can save for other editing sessions.

In the meantime, you can cross a pocket calculator off your Christmas wish list.

And Now For Something Completely Different. . .
When taking any medication, read the cautions and warnings closely. In particular, not many people realize that grapefruit juice is not compatible with a great number of medications. For the most part it does not cause an adverse reaction, but it will greatly reduce the effectiveness of the medication. Interestingly, other citrus fruits are generally not a problem.

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