diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/grammar.txt | 383 | ||||
| -rw-r--r-- | doc/manual.txt | 300 |
2 files changed, 262 insertions, 421 deletions
diff --git a/doc/grammar.txt b/doc/grammar.txt index b95af89ef..59ae5b073 100644 --- a/doc/grammar.txt +++ b/doc/grammar.txt @@ -1,204 +1,181 @@ -module ::= ([COMMENT] [SAD] stmt)* - -comma ::= ',' [COMMENT] [IND] -semicolon ::= ';' [COMMENT] [IND] - -operator ::= OP0 | OP1 | OP2 | OP3 | OP4 | OP5 | OP6 | OP7 | OP8 | OP9 - | 'or' | 'xor' | 'and' - | 'is' | 'isnot' | 'in' | 'notin' | 'of' - | 'div' | 'mod' | 'shl' | 'shr' | 'not' | 'addr' | 'static' | '..' - -prefixOperator ::= operator - -optInd ::= [COMMENT] [IND] -optPar ::= [IND] | [SAD] - -lowestExpr ::= assignExpr (OP0 optInd assignExpr)* -assignExpr ::= orExpr (OP1 optInd orExpr)* -orExpr ::= andExpr (OP2 optInd andExpr)* -andExpr ::= cmpExpr (OP3 optInd cmpExpr)* -cmpExpr ::= sliceExpr (OP4 optInd sliceExpr)* -sliceExpr ::= ampExpr (OP5 optInd ampExpr)* -ampExpr ::= plusExpr (OP6 optInd plusExpr)* -plusExpr ::= mulExpr (OP7 optInd mulExpr)* -mulExpr ::= dollarExpr (OP8 optInd dollarExpr)* -dollarExpr ::= primary (OP9 optInd primary)* - -indexExpr ::= expr - -castExpr ::= 'cast' '[' optInd typeDesc optPar ']' '(' optInd expr optPar ')' -symbol ::= '`' (KEYWORD | IDENT | operator | '(' ')' | '[' ']' | '{' '}' - | '=' | literal)+ '`' - | IDENT - -primaryPrefix ::= (prefixOperator | 'bind') optInd -primarySuffix ::= '.' optInd symbol [generalizedLit] - | '(' optInd namedExprList optPar ')' - | '[' optInd [indexExpr (comma indexExpr)* [comma]] optPar ']' - | '{' optInd [indexExpr (comma indexExpr)* [comma]] optPar '}' - -primary ::= primaryPrefix* (symbol [generalizedLit] | - constructor | castExpr) - primarySuffix* - +module = stmt ^* (';' / IND{=}) +comma = ',' COMMENT? +semicolon = ';' COMMENT? +colon = ':' COMMENT? +colcom = ':' COMMENT? + +operator = OP0 | OP1 | OP2 | OP3 | OP4 | OP5 | OP6 | OP7 | OP8 | OP9 + | 'or' | 'xor' | 'and' + | 'is' | 'isnot' | 'in' | 'notin' | 'of' + | 'div' | 'mod' | 'shl' | 'shr' | 'not' | 'addr' | 'static' | '..' + +prefixOperator = operator + +optInd = COMMENT? +optPar = (IND{>} | IND{=})? + +simpleExpr = assignExpr (OP0 optInd assignExpr)* +assignExpr = orExpr (OP1 optInd orExpr)* +orExpr = andExpr (OP2 optInd andExpr)* +andExpr = cmpExpr (OP3 optInd cmpExpr)* +cmpExpr = sliceExpr (OP4 optInd sliceExpr)* +sliceExpr = ampExpr (OP5 optInd ampExpr)* +ampExpr = plusExpr (OP6 optInd plusExpr)* +plusExpr = mulExpr (OP7 optInd mulExpr)* +mulExpr = dollarExpr (OP8 optInd dollarExpr)* +dollarExpr = primary (OP9 optInd primary)* +symbol = '`' (KEYW|IDENT|operator|'(' ')'|'[' ']'|'{' '}'|'='|literal)+ '`' + | IDENT +indexExpr = expr +indexExprList = indexExpr ^+ comma +exprColonEqExpr = expr (':'|'=' expr)? +exprList = expr ^+ comma +dotExpr = expr '.' optInd ('type' | 'addr' | symbol) +qualifiedIdent = symbol ('.' optInd ('type' | 'addr' | symbol))? +exprColonEqExprList = exprColonEqExpr (comma exprColonEqExpr)* (comma)? +setOrTableConstr = '{' ((exprColonEqExpr comma)* | ':' ) '}' +castExpr = 'cast' '[' optInd typeDesc optPar ']' '(' optInd expr optPar ')' generalizedLit ::= GENERALIZED_STR_LIT | GENERALIZED_TRIPLESTR_LIT - -literal ::= INT_LIT | INT8_LIT | INT16_LIT | INT32_LIT | INT64_LIT - | UINT_LIT | UINT8_LIT | UINT16_LIT | UINT32_LIT | UINT64_LIT - | FLOAT_LIT | FLOAT32_LIT | FLOAT64_LIT - | STR_LIT | RSTR_LIT | TRIPLESTR_LIT - | CHAR_LIT - | NIL - -constructor ::= literal - | '[' optInd colonExprList optPar ']' - | '{' optInd ':' | colonExprList optPar '}' - | '(' optInd colonExprList optPar ')' - -colonExpr ::= expr [':' expr] -colonExprList ::= [colonExpr (comma colonExpr)* [comma]] - -namedExpr ::= expr ['=' expr] -namedExprList ::= [namedExpr (comma namedExpr)* [comma]] - -exprOrType ::= lowestExpr - | 'if' expr ':' expr ('elif' expr ':' expr)* 'else' ':' expr - | 'var' exprOrType - | 'ref' exprOrType - | 'ptr' exprOrType - | 'type' exprOrType - | 'tuple' tupleDesc - -expr ::= exprOrType - | 'proc' paramList [pragma] ['=' stmt] - | 'iterator' paramList [pragma] ['=' stmt] - -exprList ::= [expr (comma expr)* [comma]] - - -qualifiedIdent ::= symbol ['.' symbol] - -typeDesc ::= (exprOrType - | 'proc' paramList [pragma] - | 'iterator' paramList [pragma] ) - ['not' expr] # for now only 'not nil' suffix is supported - -macroStmt ::= ':' [stmt] ('of' [exprList] ':' stmt - |'elif' expr ':' stmt - |'except' exceptList ':' stmt )* - ['else' ':' stmt] - -pragmaBlock ::= pragma [':' stmt] - -simpleStmt ::= returnStmt - | yieldStmt - | discardStmt - | raiseStmt - | breakStmt - | continueStmt - | pragmaBlock - | importStmt - | fromStmt - | includeStmt - | exprStmt -complexStmt ::= ifStmt | whileStmt | caseStmt | tryStmt | forStmt - | blockStmt | staticStmt | asmStmt - | procDecl | iteratorDecl | macroDecl | templateDecl | methodDecl - | constSection | letSection | varSection - | typeSection | whenStmt | bindStmt - -indPush ::= IND # and push indentation onto the stack -indPop ::= # pop indentation from the stack - -stmt ::= simpleStmt [SAD] - | indPush (complexStmt | simpleStmt) - ([SAD] (complexStmt | simpleStmt))* - DED indPop - -exprStmt ::= lowestExpr ['=' expr | [expr (comma expr)*] [macroStmt]] -returnStmt ::= 'return' [expr] -yieldStmt ::= 'yield' expr -discardStmt ::= 'discard' expr -raiseStmt ::= 'raise' [expr] -breakStmt ::= 'break' [symbol] -continueStmt ::= 'continue' -ifStmt ::= 'if' expr ':' stmt ('elif' expr ':' stmt)* ['else' ':' stmt] -whenStmt ::= 'when' expr ':' stmt ('elif' expr ':' stmt)* ['else' ':' stmt] -caseStmt ::= 'case' expr [':'] ('of' exprList ':' stmt)* - ('elif' expr ':' stmt)* - ['else' ':' stmt] -whileStmt ::= 'while' expr ':' stmt -forStmt ::= 'for' symbol (comma symbol)* 'in' expr ':' stmt -exceptList ::= [qualifiedIdent (comma qualifiedIdent)*] - -tryStmt ::= 'try' ':' stmt - ('except' exceptList ':' stmt)* - ['finally' ':' stmt] -asmStmt ::= 'asm' [pragma] (STR_LIT | RSTR_LIT | TRIPLESTR_LIT) -blockStmt ::= 'block' [symbol] ':' stmt -staticStmt ::= 'static' ':' stmt -filename ::= symbol | STR_LIT | RSTR_LIT | TRIPLESTR_LIT -importStmt ::= 'import' filename (comma filename)* -includeStmt ::= 'include' filename (comma filename)* -bindStmt ::= 'bind' qualifiedIdent (comma qualifiedIdent)* -fromStmt ::= 'from' filename 'import' symbol (comma symbol)* - -pragma ::= '{.' optInd (colonExpr [comma])* optPar ('.}' | '}') - -param ::= symbol (comma symbol)* (':' typeDesc ['=' expr] | '=' expr) -paramList ::= ['(' [param (comma|semicolon param)*] optPar ')'] [':' typeDesc] - -genericConstraint ::= 'object' | 'tuple' | 'enum' | 'proc' | 'ref' | 'ptr' - | 'var' | 'distinct' | 'iterator' | primary -genericConstraints ::= genericConstraint ( '|' optInd genericConstraint )* - -genericParam ::= symbol [':' genericConstraints] ['=' expr] -genericParams ::= '[' genericParam (comma|semicolon genericParam)* optPar ']' - - -routineDecl := symbol ['*'] [genericParams] paramList [pragma] ['=' stmt] -procDecl ::= 'proc' routineDecl -macroDecl ::= 'macro' routineDecl -iteratorDecl ::= 'iterator' routineDecl -templateDecl ::= 'template' routineDecl -methodDecl ::= 'method' routineDecl - -colonAndEquals ::= [':' typeDesc] '=' expr - -constDecl ::= symbol ['*'] [pragma] colonAndEquals [COMMENT | IND COMMENT] - | COMMENT -constSection ::= 'const' indPush constDecl (SAD constDecl)* DED indPop -letSection ::= 'let' indPush constDecl (SAD constDecl)* DED indPop - -typeDef ::= typeDesc | objectDef | enumDef | 'distinct' typeDesc - -objectField ::= symbol ['*'] [pragma] -objectIdentPart ::= objectField (comma objectField)* ':' typeDesc - [COMMENT|IND COMMENT] - -objectWhen ::= 'when' expr ':' [COMMENT] objectPart - ('elif' expr ':' [COMMENT] objectPart)* - ['else' ':' [COMMENT] objectPart] -objectCase ::= 'case' expr ':' typeDesc [COMMENT] - ('of' exprList ':' [COMMENT] objectPart)* - ['else' ':' [COMMENT] objectPart] - -objectPart ::= objectWhen | objectCase | objectIdentPart | 'nil' - | indPush objectPart (SAD objectPart)* DED indPop -tupleDesc ::= '[' optInd [param (comma|semicolon param)*] optPar ']' - -objectDef ::= 'object' [pragma] ['of' typeDesc] objectPart -enumField ::= symbol ['=' expr] -enumDef ::= 'enum' (enumField [comma] [COMMENT | IND COMMENT])+ - -typeDecl ::= COMMENT - | symbol ['*'] [genericParams] ['=' typeDef] [COMMENT | IND COMMENT] - -typeSection ::= 'type' indPush typeDecl (SAD typeDecl)* DED indPop - -colonOrEquals ::= ':' typeDesc ['=' expr] | '=' expr -varField ::= symbol ['*'] [pragma] -varPart ::= symbol (comma symbol)* colonOrEquals [COMMENT | IND COMMENT] -varSection ::= 'var' (varPart - | indPush (COMMENT|varPart) - (SAD (COMMENT|varPart))* DED indPop) +identOrLiteral = generalizedLit | symbol + | INT_LIT | INT8_LIT | INT16_LIT | INT32_LIT | INT64_LIT + | UINT_LIT | UINT8_LIT | UINT16_LIT | UINT32_LIT | UINT64_LIT + | FLOAT_LIT | FLOAT32_LIT | FLOAT64_LIT + | STR_LIT | RSTR_LIT | TRIPLESTR_LIT + | CHAR_LIT + | NIL + | tupleConstr | arrayConstr | setOrTableConstr + | castExpr +tupleConstr = '(' optInd (exprColonEqExpr comma?)* optPar ')' +arrayConstr = '[' optInd (exprColonEqExpr comma?)* optPar ']' +primarySuffix = '(' (exprColonEqExpr comma?)* ')' doBlocks? + | doBlocks + | '.' optInd ('type' | 'addr' | symbol) generalizedLit? + | '[' optInd indexExprList optPar ']' + | '{' optInd indexExprList optPar '}' +condExpr = expr colcom expr optInd + ('elif' expr colcom expr optInd)* + 'else' colcom expr +ifExpr = 'if' condExpr +whenExpr = 'when' condExpr +pragma = '{.' optInd (exprColonExpr comma?)* optPar ('.}' | '}') +identVis = symbol opr? # postfix position +identWithPragma = identVis pragma? +declColonEquals = identWithPragma (comma identWithPragma)* comma? + (':' optInd typeDesc)? ('=' optInd expr)? +identColonEquals = ident (comma ident)* comma? + (':' optInd typeDesc)? ('=' optInd expr)?) +inlTupleDecl = 'tuple' + [' optInd (identColonEquals (comma/semicolon)?)* optPar ']' +extTupleDecl = 'tuple' + COMMENT? (IND{>} identColonEquals (IND{=} identColonEquals)*)? +paramList = '(' identColonEquals ^* (comma/semicolon) ')' +paramListArrow = paramList? ('->' optInd typeDesc)? +paramListColon = paramList? (':' optInd typeDesc)? +doBlock = 'do' paramListArrow pragmas? colcom stmt +doBlocks = doBlock ^* IND{=} +procExpr = 'proc' paramListColon pragmas? ('=' COMMENT? stmt)? +expr = (ifExpr + | whenExpr + | caseExpr) + / simpleExpr +typeKeyw = 'var' | 'ref' | 'ptr' | 'shared' | 'type' | 'tuple' + | 'proc' | 'iterator' | 'distinct' | 'object' | 'enum' +primary = typeKeyw typeDescK + / prefixOperator* identOrLiteral primarySuffix* + / 'addr' primary + / 'static' primary + / 'bind' primary +typeDesc = simpleExpr +typeDefAux = simpleExpr +exprStmt = simpleExpr + (( '=' optInd expr ) + / ( expr ^+ comma + doBlocks + / ':' stmt? ( IND{=} 'of' exprList ':' stmt + | IND{=} 'elif' expr ':' stmt + | IND{=} 'except' exprList ':' stmt + | IND{=} 'else' ':' stmt )* + ))? +importStmt = 'import' optInd expr + ((comma expr)* + / 'except' optInd (expr ^+ comma)) +includeStmt = 'include' optInd expr ^+ comma +fromStmt = 'from' expr 'import' optInd expr (comma expr)* +returnStmt = 'return' optInd expr? +raiseStmt = 'raise' optInd expr? +yieldStmt = 'yield' optInd expr? +discardStmt = 'discard' optInd expr? +breakStmt = 'break' optInd expr? +continueStmt = 'break' optInd expr? +condStmt = expr colcom stmt COMMENT? + (IND{=} 'elif' expr colcom stmt)* + (IND{=} 'else' colcom stmt)? +ifStmt = 'if' condStmt +whenStmt = 'when' condStmt +whileStmt = 'while' expr colcom stmt +ofBranch = 'of' exprList colcom stmt +ofBranches = ofBranch (IND{=} ofBranch)* + (IND{=} 'elif' expr colcom stmt)* + (IND{=} 'else' colcom stmt)? +caseStmt = 'case' expr ':'? COMMENT? + (IND{>} ofBranches DED + | IND{=} ofBranches) +tryStmt = 'try' colcom stmt &(IND{=}? 'except'|'finally') + (IND{=}? 'except' exprList colcom stmt)* + (IND{=}? 'finally' colcom stmt)? +exceptBlock = 'except' colcom stmt +forStmt = 'for' symbol (comma symbol)* 'in' expr colcom stmt +blockStmt = 'block' symbol? colcom stmt +staticStmt = 'static' colcom stmt +asmStmt = 'asm' pragma? (STR_LIT | RSTR_LIT | TRIPLE_STR_LIT) +genericParam = symbol (comma symbol)* (colon expr)? ('=' optInd expr)? +genericParamList = '[' optInd + genericParam ^* (comma/semicolon) optPar ']' +pattern = '{' stmt '}' +indAndComment = (IND{>} COMMENT)? | COMMENT? +routine = optInd identVis pattern? genericParamList? + paramListColon pragma? ('=' COMMENT? stmt)? indAndComment +commentStmt = COMMENT +section(p) = COMMENT? p / (IND{>} (p / COMMENT)^+IND{=} DED) +constant = identWithPragma (colon typedesc)? '=' optInd expr indAndComment +enum = 'enum' optInd (symbol optInd ('=' optInd expr COMMENT?)? comma?)+ +objectWhen = 'when' expr colcom objectPart COMMENT? + ('elif' expr colcom objectPart COMMENT?)* + ('else' colcom objectPart COMMENT?)? +objectBranch = 'of' exprList colcom objectPart +objectBranches = objectBranch (IND{=} objectBranch)* + (IND{=} 'elif' expr colcom objectPart)* + (IND{=} 'else' colcom objectPart)? +objectCase = 'case' identWithPragma ':' typeDesc ':'? COMMENT? + (IND{>} objectBranches DED + | IND{=} objectBranches) +objectPart = IND{>} objectPart^+IND{=} DED + / objectWhen / objectCase / 'nil' / declColonEquals +object = 'object' pragma? ('of' typeDesc)? COMMENT? objectPart +distinct = 'distinct' optInd typeDesc +typeDef = identWithPragma genericParamList? '=' optInd typeDefAux + indAndComment? +varTuple = '(' optInd identWithPragma ^+ comma optPar ')' '=' optInd expr +variable = (varTuple / identColonEquals) indAndComment +bindStmt = 'bind' optInd qualifiedIdent ^+ comma +mixinStmt = 'mixin' optInd qualifiedIdent ^+ comma +pragmaStmt = pragma (':' COMMENT? stmt)? +simpleStmt = ((returnStmt | raiseStmt | yieldStmt | discardStmt | breakStmt + | continueStmt | pragmaStmt | importStmt | exportStmt | fromStmt + | includeStmt | commentStmt) / exprStmt) COMMENT? +complexOrSimpleStmt = (ifStmt | whenStmt | whileStmt + | tryStmt | finallyStmt | exceptStmt | forStmt + | blockStmt | staticStmt | asmStmt + | 'proc' routine + | 'method' routine + | 'iterator' routine + | 'macro' routine + | 'template' routine + | 'converter' routine + | 'type' section(typeDef) + | 'const' section(constant) + | ('let' | 'var') section(variable) + | bindStmt | mixinStmt) + / simpleStmt +stmt = (IND{>} complexOrSimpleStmt^+(IND{=} / ';') DED) + / simpleStmt diff --git a/doc/manual.txt b/doc/manual.txt index 8ca7b697e..3437e3e44 100644 --- a/doc/manual.txt +++ b/doc/manual.txt @@ -23,14 +23,25 @@ This document describes the lexis, the syntax, and the semantics of Nimrod. The language constructs are explained using an extended BNF, in which ``(a)*`` means 0 or more ``a``'s, ``a+`` means 1 or more ``a``'s, and -``(a)?`` means an optional *a*; an alternative spelling for optional parts is -``[a]``. The ``|`` symbol is used to mark alternatives -and has the lowest precedence. Parentheses may be used to group elements. +``(a)?`` means an optional *a*. Parentheses may be used to group elements. + +The ``|``, ``/`` symbols are used to mark alternatives and have the lowest +precedence. ``/`` is the ordered choice that requires the parser to try the +alternatives in the given order. ``/`` is often used to ensure the grammar +is not ambiguous. + Non-terminals start with a lowercase letter, abstract terminal symbols are in UPPERCASE. Verbatim terminal symbols (including keywords) are quoted with ``'``. An example:: - ifStmt ::= 'if' expr ':' stmts ('elif' expr ':' stmts)* ['else' stmts] + ifStmt = 'if' expr ':' stmts ('elif' expr ':' stmts)* ('else' stmts)? + +The binary ``^*`` operator is used as a shorthand for 0 or more occurances +separated by its second argument; likewise ``^+`` means 1 or more +occurances: ``a ^+ b`` is short for ``a (b a)*`` +and ``a ^* b`` is short for ``(a (b a)*)?``. Example:: + + arrayConstructor = '[' expr ^* ',' ']' Other parts of Nimrod - like scoping rules or runtime semantics are only described in an informal manner for now. @@ -50,7 +61,7 @@ An `identifier`:idx: is a symbol declared as a name for a variable, type, procedure, etc. The region of the program over which a declaration applies is called the `scope`:idx: of the declaration. Scopes can be nested. The meaning of an identifier is determined by the smallest enclosing scope in which the -identifier is declared. +identifier is declared unless overloading resolution rules suggest otherwise. An expression specifies a computation that produces a value or location. Expressions that produce locations are called `l-values`:idx:. An l-value @@ -93,28 +104,31 @@ Nimrod's standard grammar describes an `indentation sensitive`:idx: language. This means that all the control structures are recognized by indentation. Indentation consists only of spaces; tabulators are not allowed. -The terminals ``IND`` (indentation), ``DED`` (dedentation) and ``SAD`` -(same indentation) are generated by the scanner, denoting an indentation. +The indentation handling is implemented as follows: The lexer annotates the +following token with the preceeding number of spaces; indentation is not +a separate token. This trick allows parsing of Nimrod with only 1 token of +lookahead. + +The parser uses a stack of indentation levels: the stack consists of integers +counting the spaces. The indentation information is queried at strategic +places in the parser but ignored otherwise: The pseudo terminal ``IND{>}`` +denotes an indentation that consists of more spaces than the entry at the top +of the stack; IND{=} an indentation that has the same number of spaces. ``DED`` +is another pseudo terminal that describes the *action* of popping a value +from the stack, ``IND{>}`` then implies to push onto the stack. -These terminals are only generated for lines that are not empty. +With this notation we can now easily define the core of the grammar: A block of +statements (simplified example):: -The parser and the scanner communicate over a stack which indentation terminal -should be generated: the stack consists of integers counting the spaces. The -stack is initialized with a zero on its top. The scanner reads from the stack: -If the current indentation token consists of more spaces than the entry at the -top of the stack, a ``IND`` token is generated, else if it consists of the same -number of spaces, a ``SAD`` token is generated. If it consists of fewer spaces, -a ``DED`` token is generated for any item on the stack that is greater than the -current. These items are later popped from the stack by the parser. At the end -of the file, a ``DED`` token is generated for each number remaining on the -stack that is larger than zero. + ifStmt = 'if' expr ':' stmt + (IND{=} 'elif' expr ':' stmt)* + (IND{=} 'else' ':' stmt)? + + simpleStmt = ifStmt / ... + + stmt = IND{>} stmt ^+ IND{=} DED # list of statements + / simpleStmt # or a simple statement -Because the grammar contains some optional ``IND`` tokens, the scanner cannot -push new indentation levels. This has to be done by the parser. The symbol -``indPush`` indicates that an ``IND`` token is expected; the current number of -leading spaces is pushed onto the stack by the parser. The symbol ``indPop`` -denotes that the parser pops an item from the indentation stack. No token is -consumed by ``indPop``. Comments @@ -416,11 +430,11 @@ and not the two tokens `{.`:tok:, `.}`:tok:. Syntax ====== -This section lists Nimrod's standard syntax in ENBF. How the parser receives -indentation tokens is already described in the `Lexical Analysis`_ section. +This section lists Nimrod's standard syntax. How the parser handles +the indentation is already described in the `Lexical Analysis`_ section. Nimrod allows user-definable operators. -Binary operators have 10 different levels of precedence. +Binary operators have 10 different levels of precedence. Relevant character ------------------ @@ -1040,7 +1054,7 @@ an ``object`` type or a ``ref object`` type: .. code-block:: nimrod var student = TStudent(name: "Anton", age: 5, id: 3) -For a ``ref object`` type ``new`` is invoked implicitly. +For a ``ref object`` type ``system.new`` is invoked implicitly. Object variants @@ -1701,44 +1715,20 @@ Statements and expressions ========================== Nimrod uses the common statement/expression paradigm: `Statements`:idx: do not -produce a value in contrast to expressions. Call expressions are statements. -If the called procedure returns a value, it is not a valid statement -as statements do not produce values. To evaluate an expression for -side-effects and throw its value away, one can use the ``discard`` statement. +produce a value in contrast to expressions. However, some expressions are +statements. Statements are separated into `simple statements`:idx: and `complex statements`:idx:. Simple statements are statements that cannot contain other statements like assignments, calls or the ``return`` statement; complex statements can contain other statements. To avoid the `dangling else problem`:idx:, complex -statements always have to be intended:: - - simpleStmt ::= returnStmt - | yieldStmt - | discardStmt - | raiseStmt - | breakStmt - | continueStmt - | pragma - | importStmt - | fromStmt - | includeStmt - | exprStmt - complexStmt ::= ifStmt | whileStmt | caseStmt | tryStmt | forStmt - | blockStmt | asmStmt - | procDecl | iteratorDecl | macroDecl | templateDecl - | constSection | letSection - | typeSection | whenStmt | varSection - +statements always have to be intended. The details can be found in the grammar. Discard statement ----------------- -Syntax:: - - discardStmt ::= 'discard' expr - Example: .. code-block:: nimrod @@ -1766,16 +1756,6 @@ been declared with the `discardable`:idx: pragma: Var statement ------------- -Syntax:: - - colonOrEquals ::= ':' typeDesc ['=' expr] | '=' expr - varField ::= symbol ['*'] [pragma] - varPart ::= symbol (comma symbol)* [comma] colonOrEquals [COMMENT | IND COMMENT] - varSection ::= 'var' (varPart - | indPush (COMMENT|varPart) - (SAD (COMMENT|varPart))* DED indPop) - - `Var`:idx: statements declare new local and global variables and initialize them. A comma separated list of variables can be used to specify variables of the same type: @@ -1839,14 +1819,6 @@ For let variables the same pragmas are available as for ordinary variables. Const section ------------- -Syntax:: - - colonAndEquals ::= [':' typeDesc] '=' expr - - constDecl ::= symbol ['*'] [pragma] colonAndEquals [COMMENT | IND COMMENT] - | COMMENT - constSection ::= 'const' indPush constDecl (SAD constDecl)* DED indPop - `Constants`:idx: are symbols which are bound to a value. The constant's value cannot change. The compiler must be able to evaluate the expression in a constant declaration at compile time. @@ -1877,10 +1849,6 @@ they contain such a type. Static statement/expression --------------------------- -Syntax:: - staticExpr ::= 'static' '(' optInd expr optPar ')' - staticStmt ::= 'static' ':' stmt - A `static`:idx: statement/expression can be used to enforce compile time evaluation explicitly. Enforced compile time evaluation can even evaluate code that has side effects: @@ -1902,10 +1870,6 @@ support the FFI at compile time. If statement ------------ -Syntax:: - - ifStmt ::= 'if' expr ':' stmt ('elif' expr ':' stmt)* ['else' ':' stmt] - Example: .. code-block:: nimrod @@ -1932,12 +1896,6 @@ part, execution continues with the statement after the ``if`` statement. Case statement -------------- -Syntax:: - - caseStmt ::= 'case' expr [':'] ('of' sliceExprList ':' stmt)* - ('elif' expr ':' stmt)* - ['else' ':' stmt] - Example: .. code-block:: nimrod @@ -1998,10 +1956,6 @@ a list of its elements: When statement -------------- -Syntax:: - - whenStmt ::= 'when' expr ':' stmt ('elif' expr ':' stmt)* ['else' ':' stmt] - Example: .. code-block:: nimrod @@ -2032,10 +1986,6 @@ within ``object`` definitions. Return statement ---------------- -Syntax:: - - returnStmt ::= 'return' [expr] - Example: .. code-block:: nimrod @@ -2063,10 +2013,6 @@ variables, ``result`` is initialized to (binary) zero: Yield statement --------------- -Syntax:: - - yieldStmt ::= 'yield' expr - Example: .. code-block:: nimrod @@ -2083,10 +2029,6 @@ for further information. Block statement --------------- -Syntax:: - - blockStmt ::= 'block' [symbol] ':' stmt - Example: .. code-block:: nimrod @@ -2108,10 +2050,6 @@ block to specify which block is to leave. Break statement --------------- -Syntax:: - - breakStmt ::= 'break' [symbol] - Example: .. code-block:: nimrod @@ -2125,10 +2063,6 @@ absent, the innermost block is left. While statement --------------- -Syntax:: - - whileStmt ::= 'while' expr ':' stmt - Example: .. code-block:: nimrod @@ -2147,10 +2081,6 @@ so that they can be left with a ``break`` statement. Continue statement ------------------ -Syntax:: - - continueStmt ::= 'continue' - A `continue`:idx: statement leads to the immediate next iteration of the surrounding loop construct. It is only allowed within a loop. A continue statement is syntactic sugar for a nested block: @@ -2173,9 +2103,6 @@ Is equivalent to: Assembler statement ------------------- -Syntax:: - - asmStmt ::= 'asm' [pragma] (STR_LIT | RSTR_LIT | TRIPLESTR_LIT) The direct embedding of `assembler`:idx: code into Nimrod code is supported by the unsafe ``asm`` statement. Identifiers in the assembler code that refer to @@ -2203,8 +2130,7 @@ Example: var y = if x > 8: 9 else: 10 An if expression always results in a value, so the ``else`` part is -required. ``Elif`` parts are also allowed (but unlikely to be good -style). +required. ``Elif`` parts are also allowed. When expression --------------- @@ -2311,18 +2237,8 @@ procedure declaration defines an identifier and associates it with a block of code. A procedure may call itself recursively. A parameter may be given a default value that is used if the caller does not provide a value for this parameter. -The syntax is:: - - param ::= symbol (comma symbol)* (':' typeDesc ['=' expr] | '=' expr) - paramList ::= ['(' [param (comma param)*] [SAD] ')'] [':' typeDesc] - genericParam ::= symbol [':' typeDesc] ['=' expr] - genericParams ::= '[' genericParam (comma genericParam)* [SAD] ']' - - procDecl ::= 'proc' symbol ['*'] [genericParams] paramList [pragma] - ['=' stmt] - -If the ``= stmt`` part is missing, it is a `forward`:idx: declaration. If +If the proc declaration has no body, it is a `forward`:idx: declaration. If the proc returns a value, the procedure body can access an implicitly declared variable named `result`:idx: that represents the return value. Procs can be overloaded. The overloading resolution algorithm tries to find the proc that is @@ -2417,24 +2333,14 @@ Do notation As a special more convenient notation, proc expressions involved in procedure calls can use the ``do`` keyword: -Syntax:: - primarySuffix ::= 'do' ['(' namedExprList ')'] ['->' typeDesc] ':' - -As a start, let's repeat the example from the previous section: - .. code-block:: nimrod - cities.sort do (x,y: string) -> int: + sort(cities) do (x,y: string) -> int: cmp(x.len, y.len) ``do`` is written after the parentheses enclosing the regular proc params. The proc expression represented by the do block is appended to them. -Again, let's see the equivalent of the previous example: - -.. code-block:: nimrod - sort(cities) do (x,y: string) -> int: - cmp(x.len, y.len) -Finally, more than one ``do`` block can appear in a single call: +More than one ``do`` block can appear in a single call: .. code-block:: nimrod proc performWithUndo(task: proc(), undo: proc()) = ... @@ -2635,30 +2541,16 @@ evaluation or dead code elimination do not work with methods. Iterators and the for statement =============================== -Syntax:: - - forStmt ::= 'for' symbol (comma symbol)* [comma] 'in' expr ':' stmt - - param ::= symbol (comma symbol)* [comma] ':' typeDesc - paramList ::= ['(' [param (comma param)* [comma]] ')'] [':' typeDesc] - - genericParam ::= symbol [':' typeDesc] - genericParams ::= '[' genericParam (comma genericParam)* [comma] ']' - - iteratorDecl ::= 'iterator' symbol ['*'] [genericParams] paramList [pragma] - ['=' stmt] - The `for`:idx: statement is an abstract mechanism to iterate over the elements of a container. It relies on an `iterator`:idx: to do so. Like ``while`` statements, ``for`` statements open an `implicit block`:idx:, so that they can be left with a ``break`` statement. -The ``for`` loop declares -iteration variables (``x`` in the example) - their scope reaches until the +The ``for`` loop declares iteration variables - their scope reaches until the end of the loop body. The iteration variables' types are inferred by the return type of the iterator. -An iterator is similar to a procedure, except that it is always called in the +An iterator is similar to a procedure, except that it can be called in the context of a ``for`` loop. Iterators provide a way to specify the iteration over an abstract type. A key role in the execution of a ``for`` loop plays the ``yield`` statement in the called iterator. Whenever a ``yield`` statement is @@ -2686,9 +2578,10 @@ The compiler generates code as if the programmer would have written this: echo(ch) inc(i) -If the iterator yields a tuple, there have to be as many iteration variables +If the iterator yields a tuple, there can be as many iteration variables as there are components in the tuple. The i'th iteration variable's type is -the type of the i'th component. +the type of the i'th component. In other words, implicit tuple unpacking in a +for loop context is supported. Implict items/pairs invocations @@ -2792,23 +2685,10 @@ iterator that has already finished its work. Type sections ============= -Syntax:: - - typeDef ::= typeDesc | objectDef | enumDef - - genericParam ::= symbol [':' typeDesc] - genericParams ::= '[' genericParam (comma genericParam)* [comma] ']' - - typeDecl ::= COMMENT - | symbol ['*'] [genericParams] ['=' typeDef] [COMMENT|IND COMMENT] - - typeSection ::= 'type' indPush typeDecl (SAD typeDecl)* DED indPop - - Example: .. code-block:: nimrod - type # example demonstrates mutually recursive types + type # example demonstrating mutually recursive types PNode = ref TNode # a traced pointer to a TNode TNode = object le, ri: PNode # left and right subtrees @@ -2822,7 +2702,8 @@ Example: A `type`:idx: section begins with the ``type`` keyword. It contains multiple type definitions. A type definition binds a type to a name. Type definitions can be recursive or even mutually recursive. Mutually recursive types are only -possible within a single ``type`` section. +possible within a single ``type`` section. Nominal types like ``objects`` +or ``enums`` can only be defined in a ``type`` section. Exception handling @@ -2831,14 +2712,6 @@ Exception handling Try statement ------------- -Syntax:: - - qualifiedIdent ::= symbol ['.' symbol] - exceptList ::= [qualifiedIdent (comma qualifiedIdent)* [comma]] - tryStmt ::= 'try' ':' stmt - ('except' exceptList ':' stmt)* - ['finally' ':' stmt] - Example: .. code-block:: nimrod @@ -2863,15 +2736,14 @@ Example: close(f) - The statements after the `try`:idx: are executed in sequential order unless an exception ``e`` is raised. If the exception type of ``e`` matches any -of the list ``exceptlist`` the corresponding statements are executed. +listed in an ``except`` clause the corresponding statements are executed. The statements following the ``except`` clauses are called `exception handlers`:idx:. The empty `except`:idx: clause is executed if there is an exception that is -in no list. It is similar to an ``else`` clause in ``if`` statements. +not listed otherwise. It is similar to an ``else`` clause in ``if`` statements. If there is a `finally`:idx: clause, it is always executed after the exception handlers. @@ -2916,10 +2788,6 @@ statements. Example: Raise statement --------------- -Syntax:: - - raiseStmt ::= 'raise' [expr] - Example: .. code-block:: nimrod @@ -2948,17 +2816,21 @@ This allows for a Lisp-like `condition system`:idx:\: .. code-block:: nimrod var myFile = open("broken.txt", fmWrite) try: - onRaise(proc (e: ref E_Base): bool = + onRaise do (e: ref E_Base)-> bool: if e of EIO: stdout.writeln "ok, writing to stdout instead" else: # do raise other exceptions: result = true - ) myFile.writeln "writing to broken file" finally: myFile.close() +``OnRaise`` can only *filter* raised exceptions, it cannot transform one +exception into another. (Nor should ``onRaise`` raise an exception though +this is currently not enforced.) This restriction keeps the exception tracking +analysis sound. + Effect system ============= @@ -3447,10 +3319,6 @@ Symbol binding within templates happens after template instantiation: Bind statement -------------- -Syntax:: - - bindStmt ::= 'bind' IDENT (comma IDENT)* - Exporting a template is a often a leaky abstraction as it can depend on symbols that are not visible from a client module. However, to compensate for this case, a `bind`:idx: statement can be used: It declares all identifiers @@ -3715,18 +3583,11 @@ Statement Macros ---------------- Statement macros are defined just as expression macros. However, they are -invoked by an expression following a colon:: - - exprStmt ::= lowestExpr ['=' expr | [expr (comma expr)* [comma]] [macroStmt]] - macroStmt ::= ':' [stmt] ('of' [sliceExprList] ':' stmt - | 'elif' expr ':' stmt - | 'except' exceptList ':' stmt )* - ['else' ':' stmt] +invoked by an expression following a colon. The following example outlines a macro that generates a lexical analyzer from regular expressions: - .. code-block:: nimrod import macros @@ -3799,7 +3660,7 @@ instantiation type using the param name: var tree = new(TBinaryTree[int]) When used with macros and .compileTime. procs on the other hand, the compiler -don't need to instantiate the code multiple times, because types then can be +does not need to instantiate the code multiple times, because types then can be manipulated using the unified internal symbol representation. In such context typedesc acts as any other type. One can create variables, store typedesc values inside containers and so on. For example, here is how one can create @@ -4358,13 +4219,6 @@ the compiler encounters any static error. Pragmas ======= -Syntax:: - - colonExpr ::= expr [':' expr] - colonExprList ::= [colonExpr (comma colonExpr)* [comma]] - - pragma ::= '{.' optInd (colonExpr [comma])* [SAD] ('.}' | '}') - Pragmas are Nimrod's method to give the compiler additional information / commands without introducing a massive number of new keywords. Pragmas are processed on the fly during semantic checking. Pragmas are enclosed in the @@ -4411,10 +4265,10 @@ calls to any base class destructors in both user-defined and generated destructors. A destructor is attached to the type it destructs; expressions of this type -can then only be used in *destructible contexts*: +can then only be used in *destructible contexts* and as parameters: .. code-block:: nimrod - type + type TMyObj = object x, y: int p: pointer @@ -4425,9 +4279,15 @@ can then only be used in *destructible contexts*: proc open: TMyObj = result = TMyObj(x: 1, y: 2, p: alloc(3)) + proc work(o: TMyObj) = + echo o.x + # No destructor invoked here for 'o' as 'o' is a parameter. + proc main() = # destructor automatically invoked at the end of the scope: var x = open() + # valid: pass 'x' to some other proc: + work(x) # Error: usage of a type with a destructor in a non destructible context echo open() @@ -4849,8 +4709,8 @@ a dynamic library (``.dll`` files for Windows, ``lib*.so`` files for UNIX). The non-optional argument has to be the name of the dynamic library: .. code-block:: Nimrod - proc gtk_image_new(): PGtkWidget {. - cdecl, dynlib: "libgtk-x11-2.0.so", importc.} + proc gtk_image_new(): PGtkWidget + {.cdecl, dynlib: "libgtk-x11-2.0.so", importc.} In general, importing a dynamic library does not require any special linker options or linking with import libraries. This also implies that no *devel* @@ -4894,6 +4754,10 @@ strings, because they are precompiled. **Note**: Passing variables to the ``dynlib`` pragma will fail at runtime because of order of initialization problems. +**Note**: A ``dynlib`` import can be overriden with +the ``--dynlibOverride:name`` command line option. The Compiler User Guide +contains further information. + Dynlib pragma for export ------------------------ @@ -4971,7 +4835,7 @@ Nimrod supports the `actor model`:idx: of concurrency natively: type TMsgKind = enum mLine, mEof - TMsg = object {.pure, final.} + TMsg = object case k: TMsgKind of mEof: nil of mLine: data: string |