ref: 87e325f2c9792ece2583761ca26c57318a698be9
parent: 0283ccf588a5243b2a992d3d726c2f1344c5438a
author: seh <[email protected]>
date: Mon Mar 18 13:08:49 EDT 2019
add lists example
--- a/Lists/README.md
+++ b/Lists/README.md
@@ -1,17 +1,48 @@
# Lists
-Limbo supports lists of a type as a basic construct.
+Limbo supports lists of arbitrary types as a basic construct.
## Source
-###
+### lists.b:16,20
+Three lists are declared.
+The `len` statement can be used on a list to return the number of elements in the respective list. Note that the list `persons` is a list of tuples whose pairing is that of a string and an integer.
-## Demo
+### lists.b:22,28
+The lists `names` and `ages` are both populated.
+The `::` operator functions on lists by prepending the given element before the head of the current list. Note the interaction between successive calls to the `::` operator prior to assignment and how it affects order.
+### lists.b:30,46
+
+The list `persons` is built by making copies of the `names` and `ages` lists as `n` and `a`, respectively.
+
+The `hd` statement returns the head of the list to its right.
+
+The `tl` statement returns the tail, that is the list bar the head element, of the list to its right.
+
+An empty list is equivocal to `nil`. That is, a nil list is an empty list.
+
+Note: The effects upon temporary copies of `names` and `ages` do not affect the original lists they are copies of, as the temporary copies are copies, rather than references to the original lists.
+
+## Demo
+
+ ; limbo lists.b
+ ; lists
+ Lens: 0, 0, 0
+ Lens: 3, 3, 0
+ Persons:
+ Spike: 27
+ Jet: 36
+ Ed: 13
+ Tmp lens: 0, 0
+ Lens: 3, 3, 0
+ ;
+
## Exercises
- Try reversing a list.
+- Try interleaving two lists.
--- a/Lists/lists.b
+++ b/Lists/lists.b
@@ -3,19 +3,47 @@
include "sys.m";
include "draw.m";
-include "arg.m";
-
sys: Sys;
print: import sys;
Lists: module {- init: fn(nil: ref Draw->Context, argv: list of string);
+ init: fn(nil: ref Draw->Context, nil: list of string);
};
-init(nil: ref Draw->Context, argv: list of string) {+init(nil: ref Draw->Context, nil: list of string) {sys = load Sys Sys->PATH;
-
+ names: list of string;
+ ages: list of int;
+ persons: list of (string, int);
+
+ print("Lens: %d, %d, %d\n", len names, len ages, len persons);+
+ names = "Spike" :: names;
+ ages = 27 :: ages;
+
+ names = "Ed" :: "Jet" :: names;
+ ages = 13 :: 36 :: ages;
+
+ print("Lens: %d, %d, %d\n", len names, len ages, len persons);+
+ n := names;
+ a := ages;
+
+ while(n != nil && a != nil) {+ persons = (hd n, hd a) :: persons;
+ n = tl n;
+ a = tl a;
+ }
+
+ print("Persons:\n");+ for(; persons != nil; persons = tl persons) {+ (name, age) := hd persons;
+ print("%s: %d\n", name, age);+ }
+
+ print("Tmp lens: %d, %d\n", len n, len a);+ print("Lens: %d, %d, %d\n", len names, len ages, len persons);exit;
}
--- a/README.md
+++ b/README.md
@@ -38,6 +38,7 @@
- [Switch Case](./Switch)
- [Arrays](./Arrays)
- [Slices](./Slices)
+- [Lists](./Lists)
- [Functions](./Functions)
- [Function References](./Function-Refs)
- [Spawn](./Spawn)