Conditions

The if statement controls the program flow by the result of boolean conditions.

Structure of an if statement

In general, an if statement consists of the following elements in a fixed order:

1. an initial if followed by the condition in form of an boolean expression
2. a block of code (in { .. }) which is processed if the condition is true
3. maybe one or more else if statements with alternative conditions and code blocks
4. and last maybe an else statement followed by a code block which got executed when no other condition was true.

Conditions lead to different executions paths for different cases.

Here is a simple example:

use std::geo2d::*;

x = 0; // output changes if you change that value

if x > 0 {
    Circle(radius = 5mm);
} else if x < 0 {
    Rect(10mm);
} else {
    Hexagon(5mm);
}

Output :

if in workbenches

Inside a workbench block, an if statement can be used to select different shapes or constructions depending on input parameters. So in the following example all possible geometries are generated with parameter multiplicity and put side by side with the operation std::ops::align.

use std::ops::*;
use std::math::*;
use std::geo2d::*;

sketch MySketch(x: Integer) {
    if x > 0 {
        Circle(radius = 5mm)
    } else if x < 0 {
        Rect(10mm)
    } else {
        Hexagon(5mm)
    }
}

MySketch([-1, 0, 2]).align(X, 5mm);

Output :

if in expressions

If statements can also be used as an expression, evaluating to the value from the chosen branch.

use std::ops::*;
use std::math::*;
use std::geo2d::*;

sketch MySketch(x: Integer) {
    outer = if x > 0 {
        Circle(radius = 5mm)
    } else if x < 0 {
        Rect(10mm)
    } else {
        Hexagon(5mm)
    };

    outer - Circle(radius = 3mm)
}

MySketch([-1, 0, 1]).align(X, 5mm);

Output :