Difference between revisions of "If Command"

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* <code>f(x) = If[x < 3 ∧ x>0, x^3]</code> yields a function that equals ''sin(x)'' for x between 0 and 3 and undefined for ''x ≥ 3'' or ''x ≤ 0''.</div>}}
 
* <code>f(x) = If[x < 3 ∧ x>0, x^3]</code> yields a function that equals ''sin(x)'' for x between 0 and 3 and undefined for ''x ≥ 3'' or ''x ≤ 0''.</div>}}
 
{{note|See section: [[Boolean values]] for the symbols used in conditional statements.}}
 
{{note|See section: [[Boolean values]] for the symbols used in conditional statements.}}
 +
{{note| Derivative of  '''If[condition, f(x), g(x)]''' gives '''If[condition, f'(x), g'(x)]'''. It does not do any evaluation of limits at the critical points.}}
 
==If Command in Scripting==
 
==If Command in Scripting==
 
In many programming languages '''if''' is has the meaning "If condition holds, do something; otherwise do something else". In GeoGebra, arguments of If are not commands, but values, one of which becomes the value of the result. Therefore
 
In many programming languages '''if''' is has the meaning "If condition holds, do something; otherwise do something else". In GeoGebra, arguments of If are not commands, but values, one of which becomes the value of the result. Therefore
 
if you want to e.g. set value of ''b'' to 2 provided ''a > 2'', correct way to do this is <code>SetValue[b,If[a>2,2,b]]</code>. The other way of nesting SetValue and If is incorrect.
 
if you want to e.g. set value of ''b'' to 2 provided ''a > 2'', correct way to do this is <code>SetValue[b,If[a>2,2,b]]</code>. The other way of nesting SetValue and If is incorrect.

Revision as of 21:47, 24 September 2011


If[Condition, Object]
Yields a copy of the object if the condition evaluates to true, and an undefined object if it evaluates to false.
If[Condition, Object a, Object b]
Yields a copy of object a if the condition evaluates to true, and a copy of object b if it evaluates to false.
Warning Warning: Both objects must be of the same type.

Conditional Functions

The If command can be used to create conditional functions. Such conditional functions may be used as arguments in any command that takes a function argument, such as Derivative, Integral, and Intersect.

Example:
  • f(x) = If[x < 3, sin(x), x^2] yields a function that equals sin(x) for x < 3 and x2 for x ≥ 3
  • f(x) = If[x < 3 ∧ x>0, x^3] yields a function that equals sin(x) for x between 0 and 3 and undefined for x ≥ 3 or x ≤ 0.
Note: See section: Boolean values for the symbols used in conditional statements.
Note: Derivative of If[condition, f(x), g(x)] gives If[condition, f'(x), g'(x)]. It does not do any evaluation of limits at the critical points.

If Command in Scripting

In many programming languages if is has the meaning "If condition holds, do something; otherwise do something else". In GeoGebra, arguments of If are not commands, but values, one of which becomes the value of the result. Therefore if you want to e.g. set value of b to 2 provided a > 2, correct way to do this is SetValue[b,If[a>2,2,b]]. The other way of nesting SetValue and If is incorrect.

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