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GRAMMAR.txt
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// Below describes the entire implemented grammar of Opal
// I believe that parser is LL(2) because it needs to look
// ahead to make some decisions
// Although the parser itself is handwritten, this is the
// syntax that the following grammar adheres to:
// - "quoted" or UPPERCASE strings represent terminals
// while unquoted strings represent non-terminals
// - line breaks seperate rules instead of an explicit
// operator denoting "or"
// - [ X ] means parse X zero or one times
// - { X } means parse X zero or more times
// - X Y means parse X and then Y
// SYNTAX: toplevel
language:
{toplevel}
toplevel:
"module" ID
"use" ID
["pub"] funcDecl
["pub"] typeDecl
["pub"] ifaceDecl
implDecl
// SYNTAX: misc.
name:
ID ["::" ID]
var:
ID ":" type
varOpt:
ID [":" type]
// SYNTAX: declarations
funcDecl:
"func" ID "(" [var {"," var}] ")" funcBody
funcBody:
blockExp
"extern" "(" STRING ")" STRING "->" type
typeDecl:
"type" ID [typeParams] typeBody
typeParams:
"[" [POLYID {"," POLYID}] "]"
typeBody:
"{" [var {"," var}] "}"
"extern" "true"
"extern" "false"
"=" enumFunc {"or" enumFunc}
enumFunc:
ID "(" [type {"," type}] ")"
ifaceDecl:
"iface" [POLYID ":"] ID [typeParams] ifaceBody
ifaceBody:
"{" {ifaceFunc} "}"
ifaceFunc:
"fn" ID "(" [type {"," type}] ")" "->" type
implDecl:
"impl" [ID ":"] type implBody
implBody:
"{" {funcDecl} "}"
// SYNTAX: types
type:
name [typeArgs]
POLYID [typeIfaces]
funcType
tupleType
typeArgs:
"[" type {"," type} "]"
typeIfaces:
"(" type {"," type} ")"
funcType:
"fn" "(" [type {"," type}] ")" "->" type
tupleType:
"(" type {"," type} ")"
// SYNTAX: expressions
opControl:
"|>"
">|"
"|<"
"<|"
">>"
"<<"
opLazy:
"and"
"or"
opCmp:
"<"
"<="
"=="
"!="
">="
">"
opCons:
"$"
opAdd:
"+"
"-"
opMul:
"*"
"/"
"%"
opPow:
"^"
opUnary:
"-"
"not"
exp:
expLazy {opControl expLazy}
expLazy:
expCmp {opLazy expCmp}
expCmp:
expCons {opCmp expCons}
expCons:
expAdd [opCons expCons]
expAdd:
expMul {opAdd expMul}
expMul:
expPow {opMul term}
expPow:
term [opPow expPow]
term:
opUnary term
prefixTerm {suffix} [typeHint]
prefixTerm:
name
constant
tupleExp
fieldExp
condExp
objectExp
lambdaExp
blockExp
matchExp
suffix:
callSuffix
fieldSuffix
propertySuffix
sliceSuffix
lambdaSuffix
callSuffix:
"(" [exp {"," exp}] ")"
fieldSuffix:
"." ID
propertySuffix:
"." "(" ID ")"
sliceSuffix:
"[" "," exp "]"
"[" exp "," exp "]"
"[" exp "," "]"
"[" exp "]"
typeHint:
":" type
constant:
["-"] numberConstant
STRING
CHAR
"true"
"false"
numberConstant:
INT
REAL
LONG
tupleExp:
"(" exp {"," exp} ")"
fieldExp:
"." ID ["::" type]
condExp:
"if" exp blockExp elseExp
elseExp:
"else" condExp
"else" blockExp
objectExp:
"new" type objectInits
objectInits:
"{" [init {"," init}] "}"
init:
ID "=" exp
lambdaExp:
"fn" "(" [varOpt {"," varOpt}] ")" blockExp
lambdaSuffix:
"|" [varOpt {"," varOpt}] "|" blockExp
// SYNTAX: statements
blockExp:
"{" {stmt} [finalStmt] "}"
stmt:
";"
condStmt
whileLoop
letDecl
exp [assignment]
assignment:
"=" exp
condStmt:
"if" exp blockExp [elseStmt]
elseStmt:
"else" condStmt
"else" blockExp
whileLoop:
"while" exp blockExp
letDecl:
"let" pat "=" exp
finalStmt:
"return" [exp]
// SYNTAX: patterns
matchExp:
"match" exp matchBody
matchBody:
"{" {matchCase} "}"
matchCase:
pat "->" exp
pat blockExp
pat:
prefixPat ["$" pat]
prefixPat:
constant
ID
enumPat
tuplePat
listPat
enumPat:
name "(" [pat {"," pat}] ")"
tuplPat:
"(" [pat {"," pat}] ")"
listPat:
"[" [pat {"," pat}] "]"