Sponsored links: Algebra eBooks ### The Maxima on-line user's manual

Algebra Calculator

#### Search: #### Assume_pos_pred

-- Option variable: assume_pos_pred Default value: `false`

When `assume_pos_pred` is assigned the name of a function or a lambda expression of one argument <x>, that function is called to determine whether <x> is considered a parameter for the purpose of `assume_pos`. `assume_pos_pred` is ignored when `assume_pos` is `false`.

The `assume_pos_pred` function is called by `sign` and `asksign` with an argument <x> which is either an atom, a subscripted variable, or a function call expression. If the `assume_pos_pred` function returns `true`, <x> is considered a parameter for the purpose of `assume_pos`.

By default, a parameter is <x> such that `symbolp (<x>)` or `subvarp (<x>)`.

See also `assume` and `assume_pos`.

Examples:

```          (%i1) assume_pos: true\$
(%i2) assume_pos_pred: symbolp\$
(%i3) sign (a);
(%o3)                          pos
(%i4) sign (a);
(%o4)                          pnz
(%i5) assume_pos_pred: lambda ([x], display (x), true)\$
x = a```

```          (%o6)                          pos
x = a
1```

```          (%o7)                          pos
(%i8) asksign (foo (a));
x = foo(a)```

```          (%o8)                          pos
(%i9) asksign (foo (a) + bar (b));
x = foo(a)```

x = bar(b)

```          (%o9)                          pos
(%i10) asksign (log (a));
x = a```

Is a - 1 positive, negative, or zero?

```          p;
(%o10)                         pos
(%i11) asksign (a - b);
x = a```

x = b

x = a

x = b

Is b - a positive, negative, or zero?

```          p;
(%o11)                         neg```

```(%o1)                                true
(%i2) ```

### Related Examples

##### assume_pos_pred-pred

? assume_pos_pred;

Calculate

##### assume_pos_pred-pred

? assume_pos_pred;

Calculate

##### pred

A( r ) := 2 * %pi * r...

r : 2;

A(r);

Calculate

##### pred

A( r ) := 2 * %pi * r...

r : 2;

res : A(r);

Calculate

x=x,pred;

Calculate

? pred;

Calculate

##### pred

1<2;

1<2,pred;

Calculate 