ref: e9a441617e97091b991edb5fc90161755daaa70a
parent: c3798f64130c81c4b3e052288ef20b7710b634ac
author: Ori Bernstein <[email protected]>
date: Sun Aug 12 13:09:26 EDT 2012
Document match statements:
--- a/doc/lang.txt
+++ b/doc/lang.txt
@@ -272,8 +272,57 @@
While loops are equivalent to for loops with empty initializers
and increments. They run the test on every iteration of the loop,
- and
+ and exit only if it returns false.
+ Match statements do pattern matching on values. They take as an
+ argument a value of type 't', and match it against a list of other
+ values of the same type. The patterns matched against can also contain
+ free names, which will be bound to the sub-value matched against. The
+ patterns are checked in order, and the first matching pattern has its
+ body executed, after which no other patterns will be matched. This
+ implies that if you have specific patterns mixed with by more general
+ ones, the specific patterns must come first.
+
+ Match patterns can be one of the following:
+
+ - Union patterns
+
+ These look like union constructors, only they define
+ a value to match against.
+
+ - Literal patterns
+
+ Any literal value can be matched against.
+
+ - Constant patterns
+
+ Any constant value can be matched against.
+
+ More types of pattern to match will be added over time.
+
+ Match statements consist of the keyord 'match', followed by
+ the expression to match against the patterns, followed by a
+ newline. The body of the match statement consists of a list
+ of pattern clauses. A patterned clause is a pattern, followed
+ by a ':', followed by a block body.
+
+ An example of the syntax follows:
+
+ const Val234 = `Val 234 /* set up a constant value */
+ var v = `Val 123 /* set up variable to match */
+ match v
+ /* pattern clauses */
+ `Val 123: std.put("Matched literal union pat\n");;+
+ Val234: std.put("Matched const value pat\n");;+
+ `Val a: std.put("Matched pattern with capture\n")+ std.put("Captured value: a = %i\n", a)+ ;;
+ a std.put("A top level binding matches anything.");+ ;;
+
+
3.4. Expressions:
Myrddin expressions are relatively similar to expressions in C. The
@@ -369,8 +418,6 @@
All expressions on integers act on complement-two values which wrap
on overflow. Right shift expressions fill with the sign bit on
signed types, and fill with zeros on unsigned types.
-
-
3.5. Data Types: