ref: 9611c053041139ed398a9153877c42968caf4dfe
parent: dbf76bdbadd4ef4cd3de22b613d4c7f8492bb840
author: henesy <henesy.dev@gmail.com>
date: Tue Feb 26 05:39:13 EST 2019
add Loops
--- /dev/null
+++ b/Loops/README.md
@@ -1,0 +1,75 @@
+# Loops
+
+Looping in Limbo is similar to looping in C. Supported loop formats are for, while, and do-while.
+
+## Source
+
+### loops.b:18,23
+
+ for(i := 0; i < 10; i++){+ if(i % 2 == 0)
+ continue;
+
+ print("%d\n", i * i);+ }
+
+A for loop consists of an initialization, qualification, operation, and post-iteration sequence.
+
+Before the loop begins, but before the initial check, `i := 0` is run.
+
+After each loop iteration, `i++` is performed, then `i < 10` is checked.
+
+The `continue` keyword, from the point it is called, skips to the next loop iteration. In this case, `continue` is called if `i` is an even number. If `i` is an odd number, `i²` is printed.
+
+Note that the `continue` keyword does not skip the post-iteration operation.
+
+### loops.b:28,29
+
+ while(n)
+ print("%d\n", n--);+
+A while loop will check the qualifier for whether to enter another iteration, then, perform its operation. This loop will print the value of `n` in the range [7,1].
+
+Note that in this case the braces are omitted.
+
+### loops.b:33,36
+
+ do{+ print("%d\n", ++n);+ break;
+ }while(1);
+
+A do-while loop will perform its operation, then check the qualifier for whether to enter another iteration. In this case, the qualifier is a constant which is quantified as a true value, so, this loop would iterate forever.
+
+The `break` keyword interrupts iterative processing. In this case, it terminates the loop immediately after the print on its first iteration.
+
+Note that we reuse the value of `n`, In this case, the incremented value of `n` is printed, as when the preceding loop ends, the value of `n` is 0.
+
+## Demo
+
+ ; limbo loops.b
+ ; loops
+ == for
+ 1
+ 9
+ 25
+ 49
+ 81
+ == while
+ 7
+ 6
+ 5
+ 4
+ 3
+ 2
+ 1
+ == do
+ 1
+ ;
+
+## Exercises
+
+- Try reversing the ++/-- operators in different places, what happens?
+- Try omitting various portions of the for loop syntax, what happens?
+- Is `for(;;);` an infinite loop?
+- Make the condition for a loop something similar to --n, how many iterations does it run for?
--- /dev/null
+++ b/Loops/loops.b
@@ -1,0 +1,39 @@
+implement Loops;
+
+include "sys.m";
+include "draw.m";
+
+sys: Sys;
+print: import sys;
+
+Loops: module {+ init: fn(nil: ref Draw->Context, nil: list of string);
+};
+
+init(nil: ref Draw->Context, nil: list of string) {+ sys = load Sys Sys->PATH;
+
+ print("== for\n");+
+ for(i := 0; i < 10; i++){+ if(i % 2 == 0)
+ continue;
+
+ print("%d\n", i * i);+ }
+
+ print("== while\n");+
+ n := 7;
+ while(n)
+ print("%d\n", n--);+
+ print("== do\n");+
+ do{+ print("%d\n", ++n);+ break;
+ }while(1);
+
+ exit;
+}
--- a/Values/README.md
+++ b/Values/README.md
@@ -9,6 +9,8 @@
sys: Sys;
print, sprint: import sys;
+The name `sys` is declared as type `Sys`. If you are defining a type for a name, the format is: `varname: typename`.
+
The `import` statement allows you to define a local name which is tied to a name in another space. That is, the `print` name becomes equivalent to `sys->print`.
### values.b:16,19