ref: 4f9a890e8007fc30b768415c42dfa8cd76057055
parent: fefdce5c957865ebcf2e30c99b5ff1b6e09e0efb
author: Ori Bernstein <ori@eigenstate.org>
date: Sat Jan 14 17:16:23 EST 2017
Clarify function literals.
--- a/doc/lang.txt
+++ b/doc/lang.txt
@@ -6,8 +6,9 @@
TABLE OF CONTENTS:
1. ABOUT
- 2. NOTATION
+ 2. NOTATION AND SEMANTICS
2.1. Grammar
+ 2.2. As-If Rule
3. LEXICAL CONVENTIONS
3.1. Summary
4. SYNTAX
@@ -45,7 +46,7 @@
ML, with ideas from too many other places to name.
-2. NOTATION:
+2. NOTATION AND SEMANTICS:
2.1. Grammar:
@@ -62,6 +63,12 @@
zerorep: expr "*"
onerep: expr "+"
+ 2.2. As-If Rule:
+
+ Anything specified here may be treated however the compiler wishes,
+ as long as the result is observed as if the semantics specified were
+ followed strictly.
+
3. LEXICAL CONVENTIONS:
3.1. Summary:
@@ -262,24 +269,25 @@
4.2.2. Sequence and Tuple Literals:
- seqlit: "[" structelts | arrayelts "]"
- structelts:
- arrayelts:
+ seqlit: "[" structelts | arrayelts "]"
+ tuplit: "(" tuplelts ")"- tuplit: "(" tuplelts ")"- tupelts: expr
+ structelts: ("." ident "=" expr)++ arrayelts: (expr ":" expr | expr)*
+ tupelts: expr ("," expr)* [","]- 4.2.3. Function Literals
+ Sequence literals are used to initialize either a structure
+ or an array. They are '['-bracketed expressions, and are evaluated
+ Tuple literals are similarly used to initialize a tuple.
- Function literals describe a function. They begin with a '{',- followed by a newline-terminated argument list, followed by a
- body and closing '}'. They will be described in more detail
- later in this manual.
+ Struct literals describe a fully initialized struct value.
+ A struct must have at least one member specified, in
+ order to distinguish them from the empty array literal. All
+ members which are designated with a `.name` expression are
+ initialized to the expression passed. If an initializer is
+ omitted, then the value is initialized to the zero value for
+ that type.
- eg: {a : int, b- -> a + b
- }
-
Sequence literals describe either an array or a structure
literal. They begin with a '[', followed by an initializer
sequence and closing ']'. For array literals, the initializer
@@ -294,13 +302,66 @@
initializer sequence contains a comma separated list of
'.name=value' pairs.
- eg: [1,2,3], [#2=3, #1=2, #0=1], [.a = 42, .b="str"]
A tuple literal is a parentheses separated list of values.
A single element tuple contains a trailing comma.
- eg: (1,), (1,'b',"three")
+ Example: Struct literal.
+ [.a = 42, .b="str"]
+ Example: Array literal:
+ [1,2,3], [2:3, 1:2, 0:1],
+
+ Example: Tuple literals:
+ (1,), (1,'b',"three")
+
+
+ 4.2.3. Function Literals:
+
+ funclit: "{" arglist "\n" blockbody "}"+ arglist: (ident [":" type])*
+
+ Function literals describe a function. They begin with a '{',+ followed by a newline-terminated argument list, followed by a
+ body and closing '}'. These may be specified at any place that
+ an expression is specified, assigned to any variable, and are
+ not distinguished from expressions in any significant way.
+
+ Function literals may refer to variables outside of their scope.
+ These are treated differently in a number of ways. Variables with
+ global scope are used directly, by value.
+
+ If a function is defined where stack variables are in scope,
+ and it refers to them, then the stack variables shall be copied
+ to an environment on thes stack. That environment is scoped to
+ the lifetime of the stack frame in which it was defined. If it
+ does not refer to any of its enclosing stack variables, then
+ this environment will not be created or accessed by the function.
+
+ This environment must be transferrable to the heap in an
+ implementation specific manner.
+
+ Example: Empty function literal:
+ {;}+
+ Example: Function literal
+
+ {a : int, b+ -> a + b
+ }
+
+ Example: Nested function with environment:
+
+ const fn = {a+ var b = {; a + 1}+ }
+
+
+ 4.2.4: Labels:
+
+ label: ":" ident
+ goto: "goto" ident
+
Finally, while strictly not a literal, it's not a control
flow construct either. Labels are identifiers preceded by
colons.
@@ -313,8 +374,18 @@
the ':' is not part of the label name.
+ 4.3. Blocks:
- 4.3. Control Constructs and Blocks:
+ block: blockbody ";;"
+ blockbody: (decl | stmt | tydef | "\n")*
+ stmt: goto | break | continue | retexpr | label |
+ ifstmt | forstmt | whilestmt | matchstmt
+
+ Blocks are the basic building block of functionality in Myrddin.
+ They are simply sequences of statements that are completed one after
+ the
+
+ 4.3. Control Constructs:
if for
while match