GeoGebraCAS Blog

2011-09-05: GeoGebraCAS in 4.2 Beta =

In Spring 2011 we have moved from MathPiper and Maxima to using MPReduce only. The CAS view is currently part of GeoGebra 4.2 Beta and will be officially released with GeoGebra 4.2.

2010-04-18: GeoGebraCAS 3.3.110.0

• New commands: LeftSide[<equation>], RightSide[<equation>]. These commands also work for the result of Solve, e.g. RightSide[{x=3/2}]
• Toolbar commands for Solve, Derivative, and Integral try variable x first. If the current expression does not contain x, then the first variable in alphabetic order of the expression is used. Thus, 3y+5=7 can be solved for y now by simply choosing Solve from the toolbar.
• Check input for assignments: a := 2 + 2 now keeps the input unevaluated when you press Ctrl+Enter
• Input of equations is now possible using both : and := notation, e.g. g: 3x + 4y = 7 or g := 3x + 4y = 7
• Fixed display of exponents in output, e.g. (x+y)² and press Ctrl+Enter
• (7*3)/(5*2) with Ctrl+Enter is now displayed as a single fraction
• Delete rows by selecting them with the mouse and then pressing the Delete key
• Update to MathPiper version 0.79b

2010-04-08: GeoGebraCAS 3.3.103.0

• Substitute improvements
  • click on an existing row inserts text into substitute dialog's text field
  • substitute dialog's text fields now allow the use of row references ($ or # notation)
  • substitute dialog now always stays on top of GeoGebra window
  • Substitute[1.05 * 1.05 K1, K1, K0 * 1.05] now gives 1.05 * 1.05 * 1.05 K0 instead of 1.1025 * 1.05 K0. Same from Substitute dialog.
• Output command comments saveable: Used toolbar commands are saved (e.g. "Factor") with CAS sessions now. After reloading a file, you can see the comments next to the respective outputs.
• Command translations: all entered commands are internally translated. This will allow creating a CAS session with German commands and then translating it by simply switching GeoGebra's language.
• Improved assignment output: function expressions are kept as entered, e.g. f(x) := (1/2)*(x+2/x)
• Multiplication signs and spaces improved in output: Integral[ a sin(x),x] now shows a clear space in "-a cos(x)"
• "New file" now removes all variable and function definitions in CAS view
• Fixed # row references and added support for nested row references
• max/min CAS view window now keeps content
• change CAS view width while editing row now keeps current input
• Update to MathPiper version 0.78z

2010-03-07: GeoGebraCAS 3.3.70.0

New features

• Dynamic CAS View: dependent rows are evaluated automatically. The new CAS view is now fully dynamic, making it a true "GeoGebraCAS". This means that dependencies between the CAS view rows are respected and lead to automatic evaluation of other rows. For example, when you evaluate a row with a:=5, all dependent rows below like b := a + 5, c := b/2 are evaluated automatically too. This automatic evaluation always goes from top to bottom starting at the changed row.
• Full connection to GeoGebra: variables are updated between the CAS view and GeoGebra.
• Adding equations, e.g. first row: 3x+6y=7, second row: x-y=2, then you can use $1 +6 $2 to add the two equations ($1, $2 are dynamic references to the first and second row). If you also want to draw the equations, you can label them, e.g. first row a: 3x+6y=7, second row b: x-y=2, then add them in the third row using a + 6b
• Solve and Solutions: Solve[x^2=4] returns {x=-2, x=2} while Solutions[x^2=4] returns {-2,2}
• For convenience, the following input is automatically rewritten:
  • a:= is rewritten as Delete[a] and deletes/unbinds variable a
  • 2+2= is rewritten as 2+2 by removing the trailing =
  • f(x)=x^2 is rewritten as f(x):=x^2
  • Note that a=3 is no longer rewritten as a:=3 to allow equations of this form too.

Changes

• Dynamic row references now use the $ sign instead of %. The $ sign is already used in the spreadsheet, so it makes sense to reuse it here and keep % to allow easy input of percentages in the future.

• = now always automatically performs simplify. The simplify toolbar command has been removed.

Fixes

• Selections now always check the structure of expressions. Consider the input 2 + 2/3. When you select 2 + 2 and choose Evaluate (=) from the toolbar, the old version returned the incorrect result 4/3. Now, this structural selection problem is detected and yields an error message.
• Solve2 and Solutions2 now work correctly for (simple) systems of two equations
• -5 Ctrl+Enter (Hold) no longer gives -1 * 5 but now -5
• Variable assignments for x and y are now allowed in the CAS view, e.g. x := 5 and y := 7. Note that the values of x and y cannot be used in the rest of GeoGebra as they remain reserved for functions and equations there.

Notes

• output of assignments: a := 3 returns 3 and f(x) := x^2 returns x^2 as output instead of "defined" because we also want f(x) := Derivative[x^2] to return 2*x and not just "defined". Note that you can suppress the output by using a semicolon at the end, e.g. a := 3;

2010-01-27: GeoGebraCAS 3.3.56.0

• Synchronization of variables: Functions and variable definitions are now automatically synchronized between GeoGebraCAS and the rest of GeoGebra, e.g. you can define a function f(x) := x^2 or variable a := 5 in GeoGebraCAS or the GeoGebra input bar and it will be available everywhere. If you then delete f(x) or a in GeoGebra, it will be undefined in GeoGebraCAS afterwards too. In GeoGebraCAS, you can delete objects by using e.g. Delete[f] or Delete[a]
• Assignment convenience: GeoGebraCAS requires := notation for assignments in order to distinguish an assignment a := b + 5 from an equation a = b + 5. In order to help the user, an input like f(x) = x^2 is now automatically rewritten as f(x) := x^2, and a = 5 is rewritten as a := 5.
• Suppress output: a semicolon at the end of the input line keeps the output hidden. This is useful to suppress the output of assignments, e.g. a := 5;
• fixed: g(x) := Derivative[x^2], then g(2) now works correctly. Internally, the right hand side of an assignment is now always evaluated first.
• fixed: Factor command improved: Factor[ a^2 + 2 a b + b^2 ] now gives (a+b)^2
• includes MathPiper update .78f

2010-01-12: GeoGebraCAS 3.3.52.0

• includes MathPiper update .78a
• added command information to the output of a row, so you know what you did
• new equation manipulation based on flexible pattern rules, also added auto-simplification of equation manipulations to ensure that e.g. (5x = 10) / 5 gives x = 2 instead of (5x)/5 = 2
• default numeric precision of the CAS is now 16 significant figures. With SetPrecision[32] can be used to change the default precision. Note that you can always change the precision for a single computation using N[sqrt(2), 20].
• added support for functions of any variable name, e.g. a(n) := 3n + 1
• Solve2 command for systems of equations (needs some internal improvements on the MathPiper side)
• dynamic row references with %
• fixed #19, Sequence problem: no more labels shown with Sequence[(n, 1), n, 1, 10]