The tour, 3 of 11

Control flow

If, For, While, Repeat, Loop, Select, and Defer, each block with its End.

Every block ends with End and its kind: End If, End For, End While. There’s no Next, Wend, or EndIf, and no Goto.

If

Import std.core

Local hp = 15

If hp <= 0
    Print("dead")
ElseIf hp < 20
    Print("hurt")
Else
    Print("fine")
End If

If hp < 20 Then Print("find a medkit")     // one line takes Then, and no End If

Output

hurt
find a medkit

&&, ||, and ! are logical and stop as soon as they know the answer; the bitwise operators are &, |, ^, and ~.

For

To counts up to and including its end, and Until stops before it. For ... In goes over an array, a range, a Map, or anything with an iterator, and can take the index too.

Import std.core

For i = 1 To 3
    Write("{i} ")
End For
Print()

For i = 0 Until 10 Step 3
    Write("{i} ")
End For
Print()

Local names = ["Ada", "Grace", "Alan"]
For i, name In names
    Print("{i}: {name}")
End For

Print((1 To 10).Sum())

Output

1 2 3 
0 3 6 9 
0: Ada
1: Grace
2: Alan
55

While, Repeat, and Loop

Import std.core

Local n = 27
Local steps = 0
While n != 1
    If n % 2 == 0 Then n = n / 2 Else n = 3 * n + 1
    steps += 1
End While
Print("27 takes {steps} steps")

Local tries = 0
Repeat                      // the body runs at least once
    tries += 1
Until tries >= 3
Print("tried {tries} times")

Local frame = 0
Loop                        // until a Break
    frame += 1
    If frame == 5 Then Break
End Loop
Print("stopped at frame {frame}")

Output

27 takes 111 steps
tried 3 times
stopped at frame 5

Break and Continue take a loop’s label to leave or go on with an outer one: Outer: For y = ... then Break Outer.

Select

Import std.core

For roll In [1, 4, 6, 9]
    Select roll
        Case 1
            Print("{roll}: a miss")
        Case 2 To 5
            Print("{roll}: a hit")
        Case 6, 7, 8
            Print("{roll}: a critical")
        Default
            Print("{roll}: off the table")
    End Select
End For

Output

1: a miss
4: a hit
6: a critical
9: off the table

Defer

Defer runs a statement when its block ends, however it ends, for what has to be closed or put back.

Import std.core

Function Load()
    Print("open the level")
    Defer Print("close the level")
    Print("read the level")
End Function

Load()

Output

open the level
read the level
close the level

Next: Functions.

Next: Functions

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