# EXPRESSION

Mathematical expression

### Description

The Expression block applies the specified Scilab expressions to its input.

### Parameters

• number of inputs

Block input can be a scalar or vector.

Properties : Type 'vec' of size 1

• scilab expression

The Scilab expression applied to the input.

Properties : Type 'vec' of size 1

All Scilab operators are supported.

Only a restricted list of functions are supported in the expression.

Name#rhs
sin 1
cos 1
tan 1
asin 1
acos 1
atan 1
atan2 2
Name #rhs
sinh 1
cosh 1
tanh 1
asinh 1
acosh 1
atanh 1
Name#rhs
exp 1
log 1
log10 1
int 1
round 1
ceil 1
floor 1
Name#rhs
sign 1
abs 1
min 2
max 2

 In the provided expression, any subexpression being an exponent more than 1-character long must end with a space, to be correctly displayed on the block's icon. This constrain has no consequence on the computational validity of the expression. Examples: "u1^12-u2", "u1^ 12-u2", "u1^abc - 3", "u1^(u2-3) + 4" will be correctly displayed, while "u1^abc-3" would be displayed as "u1^{abc-3}" (but well computed as `u1^abc + 3`) and "u1^(u2-3)+4" as "u1^{(u2-3)+4}" instead of "u1^{(u2-3)} + 4". "u1^abc - 3" and "u1^(u2-3) + 4" will have to be entered instead.
• use zero-crossing

Select to enable zero crossing detection.

Properties : Type 'vec' of size 1

### Default properties

• always active: no

• direct-feedthrough: yes

• zero-crossing: yes

• mode: yes

• regular inputs:

- port 1 : size [1,1] / type 1

- port 2 : size [1,1] / type 1

• regular outputs:

- port 1 : size [1,1] / type 1

• number/sizes of activation inputs: 0

• number/sizes of activation outputs: 0

• continuous-time state: no

• discrete-time state: no

• object discrete-time state: no

• name of computational function: evaluate_expr

### Example

The following example calculate an arbitrary expression with multiple different configuration or blocks.

y = u(1) - u(2) - u(3)

### Interfacing function

• SCI/modules/scicos_blocks/macros/NonLinear/EXPRESSION.sci

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