1. for
   • General Form
   • Keywords
     • index
     • step
     • reverse
     • start & end
   • Keywords Inside Loop
     • more
     • first
     • last
2. while
   • General Form
3. do..while
   • General Form

for

Use for statements to loop over a statement for a specified number of values.

General Form

    for (controlVariable in values) {
	stmt;
    }

where ''values'' can be:

a simple integer range defined like:

    first..last

or an iterable data collection like:

• sequence
• set
• enum
• map

Examples

{
    for (i in 1..10) {
        pln(#i);
    }
}

{
    Object[] seq();
    seq << "Hello" << "World" << Int(8) << Double(2.3) << "Dude";

    for (o in seq) {
        pln(#o);
    }
}

{
    str->int nameToAge();
    nameToAge.put("Joan", 41);
    nameToAge.put("Mike", 32);
    nameToAge.put("John", 55);

    for (n, a in nameToAge) {
        pln(n, " is ", a, " years old");
    }
}

Keywords

index

The value of the current index of the loop.

{
    for (n in 1..5, index=i) {
        pln(#i; #n);
    }
}

Output:
i=0, n=1
i=1, n=2
i=2, n=3
i=3, n=4
i=4, n=5

{
    int[] values();
    values << 3 << 8 << 10 << 31 << 100;
    
    for (n in values, index=i) {
        pln(#i; #n);
    }
}

Output:
i=0, n=3
i=1, n=8
i=2, n=10
i=3, n=31
i=4, n=100

step

Iterate in steps. Applicable for numerics.

{
    for (n in 1..5, index=i, step=2) {
        pln(#i; #n);
    }
}

Output:
i=0, n=1
i=1, n=3
i=2, n=5

{
    for (d in 1..1.74, step=.2) {
        pln(#d);
    }
}

Output:
d=1
d=1.2
d=1.4
d=1.6

reverse

Iterate backward. Applicable for sequences, sorted maps, and strings.

{
    int[] values();
    values << 3 << 8 << 10 << 31 << 100;
    
    for (n in values, index=i, reverse) {
        pln(#i; #n);
    }
}

Output:
i=4, n=100
i=3, n=31
i=2, n=10
i=1, n=8
i=0, n=3

start & end

Start and end iteration at the given index. Applicable for sequences and strings.

private str txt = "A simple text";

{
    for (s in txt, start=9) {
        pln(s);
    }
}

Output:
t
e
x
t

{
    for (s in txt, end=7) {
        pln(s);
    }
}

Output:
A
 
s
i
m
p
l
e

{
    for (s in txt, start=2, end=7) {
        pln(s);
    }
}

Output:
s
i
m
p
l
e

{
    for (s in txt, start=7, end=2, reverse) {
        pln(s);
    }
}

Output:
e
l
p
m
i
s

Keywords Inside Loop

Some boolean keywords exist for convenience during iteration.

more

Is true if there are more values, i.e. if the loop will iterate at least one more time.

{
    str[] lines();
    lines << "First line" << "Second line" << "Third line";
    StrBuf buf();
    for (l in lines) {
        buf << l;
        if (more) buf << "\n";
    }
    pln(buf);
}

Output:
First line
Second line
Third line

first

Is true if this is the first iteration.

{
    point ref(1, 1, 1);
    point{} allPositions();
    allPositions << (0, 0, 0) << (1, 0, 1) << (0, 2, 1);
    point closest;
    
    for (p in allPositions) {
        if (first) {
            closest = p;
        } else {
            if (ref.distance(p) < ref.distance(closest)) {
                closest = p;
            }
        }
    }
}

last

Is true if this is the last iteration.

{
    str[] linesWLF();
    linesWLF << "First line\n" << "Second line\n" << "Third line\n";
    StrBuf buf();
    for (l in linesWLF) {
        buf << l;
        if (last) buf.dropLast();
    }
    pln(buf);
}

Output:
First line
Second line
Third line

while

Use while statements to loop over a statement as long as a specified condition is fulfilled.

General Form

    while (condition) {
	stmt;
    }

Another possibility is to include initialization and/or increment in the while statement.

    while (initialization; condition; increment) {
	stmt;
    }

Examples

{
    int i = 0;
    while (i < 100) {
        pln(#i);
        i++;
    }
}

{
    while (int i = 0; i <= 10; i++) {
        pln(#i);
    }
}

{
    int maxLength = 1024;
    int count;
    StrBuf txt();
    Url url("c:\\temp\\testFile.txt");
    if (url.isReadable) {
        if (File input = openForRead(url)) {
            pln("Opened file");
            while (input.more) {
                count++;
                if (count > maxLength) {
                    pln("Stopped reading");
                    break;
                }
                char next = input.get().char;
                txt << next;
            }
            input.close();
            pln("Read ", txt.count, " characters from ", url);
        }
    } else {
        pln("Not readable: ", url);
    }
}

do..while

A do while-loop executes a block of code at least once, and then repeatedly executes the block, or not, depending on a given condition at the end of the block.

General Form

    do {
	stmt;
    } while condition

Example

{
    int i = 0;
    do {
        pln(#i);
    } while (i++ < 10);
}