831 lines
24 KiB
Nim
831 lines
24 KiB
Nim
import strformat
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import strutils
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import sugar
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import scanner
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import chunk
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import types/value
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import bitops # needed for value
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import config
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type
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Local = object
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name: string # name of this local
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index: int # what is its index in the stack (0 is the stack bottom - nil in the main function)
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depth: int # depth of this local
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# if depth is -1, the variable cannot be referenced yet
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# its depth will be set once its first ever value is determined
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Scope = ref object
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labels: seq[string]
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#depth: int
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goalStackIndex: int # the stack count it started with plus 1
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jumps: seq[int] # jumps to be patched that jump to the end
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function: bool # if true, it is a function
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Compiler = ref object
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#
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# input
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#
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scanner: Scanner
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source: string
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#
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# state
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#
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previous: Token
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current: Token
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canAssign: bool
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locals: seq[Local]
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scopes: seq[Scope]
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stackIndex: int # how large the stack is
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# when there's an error both are set
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# panic mode can be turned off e.g. at block boundaries
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panicMode: bool
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#
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# output
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#
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chunk*: Chunk
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hadError*: bool
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Precedence = enum
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pcNone, pcAssignment, pcOr, pcAnd, pcEquality, pcComparison,
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pcTerm, pcFactor, pcUnary, pcIndex, pcCall, pcPrimary
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# pcUnary applies to all prefix operators regardless of this enum's value
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# changing pcUnary's position can change the priority of all unary ops
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#
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# Note: unary only rules should have precedence pcNone!!!
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ParseRule = object
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name: string # debug purposes only
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prefix: (Compiler) -> void
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infix: (Compiler) -> void
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prec: Precedence # only relevant to infix, prefix always has pcUnary
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proc newScope(comp: Compiler, function: bool): Scope =
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result.new()
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#result.depth = comp.scopes.len + 1
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result.function = function
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result.goalStackIndex = comp.stackIndex + 1
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comp.scopes.add(result)
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# HELPERS FOR THE COMPILER TYPE
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proc newCompiler*(name: string, source: string): Compiler =
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result = new(Compiler)
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result.chunk = initChunk(name)
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result.source = source
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result.hadError = false
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result.panicMode = false
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result.canAssign = true
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result.locals = @[]
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result.scopes = @[]
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proc errorAt(comp: Compiler, line: int, msg: string, at: string = "") =
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if comp.panicMode:
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return
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write stderr, &"[line {line}] Error "
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if at.len > 0:
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write stderr, &"at {at} "
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write stderr, msg
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write stderr, "\n"
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comp.hadError = true
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comp.panicMode = true
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proc error(comp: Compiler, msg: string) =
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## create a simple error message
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comp.errorAt(comp.previous.line, msg)
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proc errorAtCurrent(comp: Compiler, msg: string) =
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comp.errorAt(comp.current.line, msg)
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proc advance(comp: Compiler) =
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comp.previous = comp.current
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while true:
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comp.current = comp.scanner.scanToken()
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when debugScanner:
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comp.current.debugPrint()
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if (comp.current.tokenType != tkError):
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break
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comp.errorAtCurrent(comp.current.text)
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proc match(comp: Compiler, tokenType: TokenType): bool =
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if comp.current.tokenType == tokenType:
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comp.advance()
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true
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else:
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false
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proc consume(comp: Compiler, tokenType: TokenType, msg: string) =
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if comp.current.tokenType == tokenType:
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comp.advance()
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else:
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comp.errorAtCurrent(msg)
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proc synchronize(comp: Compiler) =
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comp.panicMode = false
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while comp.current.tokenType != tkEof:
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if comp.previous.tokenType in {tkSemicolon, tkRightBrace}:
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return
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if comp.current.tokenType in {tkFunct, tkVar, tkFor, tkIf, tkWhile}:
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return
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comp.advance()
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proc writeChunk(comp: Compiler, dStackIndex: int, ch: OpCode | DoubleUint8 | uint8) =
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comp.stackIndex += dStackIndex
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when debugCompiler:
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debugEcho &"new stackindex: {comp.stackIndex}, delta: {dStackIndex} due to {ch.repr}"
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comp.chunk.writeChunk(ch, comp.previous.line)
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proc writePops(comp: Compiler, count: int) =
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if count > argMax:
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comp.error("Too many local variables in block.")
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if count == 0:
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return
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when debugCompiler:
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debugEcho &"Emitting {count}xPop."
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if count == 1:
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comp.writeChunk(-1, opPop)
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elif count < shortArgMax:
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comp.writeChunk(-count, opPopSA)
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comp.writeChunk(0, count.uint8)
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else:
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comp.writeChunk(-count, opPopA)
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comp.writeChunk(0, count.toDU8())
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proc writeConstant(comp: Compiler, constant: NdValue) =
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comp.stackIndex.inc
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let index = comp.chunk.writeConstant(constant, comp.previous.line)
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if index >= argMax:
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comp.error("Too many constants in one chunk.")
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proc addLocal(comp: Compiler, name: string, delta: int) =
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if comp.locals.len >= argMax:
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comp.error("Too many local variables in function.")
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# if delta is 0 or negative, it means that it is already on the stack when addLocal is called
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# if delta is positive, the first ever value of the local is to the right
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comp.locals.add(Local(name: name, depth: if delta > 0: -1 else: comp.scopes.high, index: comp.stackIndex + delta))
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proc markInitialized(comp: Compiler) =
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comp.locals[comp.locals.high].depth = comp.scopes.high
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# PARSE RULE/PRECEDENCE MISC
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proc nop(comp: Compiler) = discard
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var rules: array[TokenType, ParseRule]
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template genRule(ttype: TokenType, tprefix: (Compiler) -> void, tinfix: (Compiler) -> void, tprec: Precedence) =
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if tprec == pcUnary:
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raise newException(Exception, "pcUnary cannot be used as a rule precedence! Use pcNone for unary-only rules!")
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elif tprec == pcPrimary:
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raise newException(Exception, "Invalid rule: pcPrimary cannot be used for binary operators, if this rule is for a primary value, use pcNone!")
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elif tprec == pcNone and tinfix != nop:
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raise newException(Exception, "Invalid rule: pcNone only allowed for unary operators and primary values, not for infix ones!")
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rules[ttype] = ParseRule(name: $ttype, prefix: tprefix, infix: tinfix, prec: tprec)
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for i in TokenType:
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genRule(i, nop, nop, pcNone)
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proc getRule(opType: TokenType): ParseRule =
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rules[opType]
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proc applyRule(rule: ParseRule): Precedence =
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# returns the rule's precedence
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rule.prec
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proc increment(prec: Precedence): Precedence =
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# increases precedence by one
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if prec == pcPrimary:
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raise newException(Exception, "Invalid ruletable, pcPrimary precedence increment attempted.")
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else:
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Precedence(int(prec) + 1)
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proc `<=`(a, b: Precedence): bool =
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int(a) <= int(b)
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# JUMP HELPERS
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proc emitJump(comp: Compiler, delta: int, op: OpCode): int =
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# delta -> 0 if the jump does not pop
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# delta -> -1 if the jump pops the condition from the stack
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comp.writeChunk(delta, op)
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comp.writeChunk(0, 0xffffff.toDU8)
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comp.chunk.len - argSize
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proc patchJump(comp: Compiler, offset: int) =
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let jump = (comp.chunk.len - offset - argSize)
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if (jump > argMax):
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comp.error("Too much code to jump over.")
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let jumpt = jump.toDU8
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comp.chunk.code[offset] = jumpt[0]
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comp.chunk.code[offset + 1] = jumpt[1]
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proc emitLoop(comp: Compiler, loopstart: int, delta: int, op: OpCode) =
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comp.writeChunk(delta, op)
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let offset = comp.chunk.len - loopstart + argSize
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if offset > argMax:
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comp.error("Loop body too large.")
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comp.writeChunk(0, offset.toDU8)
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# SCOPE HELPERS
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proc beginScope(comp: Compiler, function: bool = false) =
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let scope = comp.newScope(function)
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when debugCompiler:
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debugEcho &"Begin scope called for depth {comp.scopes.len} function? {function}"
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if function:
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scope.labels.add("result")
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scope.labels.add("function")
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else:
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while comp.match(tkLabel):
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let label = comp.previous.text[1..^1]
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scope.labels.add(label)
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if function:
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# if it's a function scope, the frame will move
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# access to outside locals is also limited to upvalues and closures
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comp.stackIndex = 0
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else:
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# only put the opNil if it's not a function scope, since
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# function scopes are initialized by the caller
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comp.writeChunk(1, opNil)
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for label in scope.labels:
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comp.addLocal(&":{label}", delta = 0)
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proc restore(comp: Compiler, scope: Scope) =
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let delta = comp.stackIndex - scope.goalStackIndex
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comp.writePops(delta)
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when assertionsCompiler:
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if not comp.stackIndex == scope.goalStackIndex:
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comp.error("Assertion failed in restore")
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when debugCompiler:
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debugEcho &"Restored scope: delta {delta}"
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proc restoreInFunct(comp: Compiler, scope: Scope) =
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let pops = comp.stackIndex
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comp.writePops(pops)
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comp.stackIndex = scope.goalStackIndex
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when debugCompiler:
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debugEcho &"Restored function scope: delta {pops}; new stackindex: {comp.stackIndex}"
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proc jumpToEnd(comp: Compiler, scope: Scope) =
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## Jumps to the end of scope, does not affect stackIndex
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var delta: int
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if scope.function:
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delta = comp.stackIndex
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else:
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delta = comp.stackIndex - scope.goalStackIndex
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comp.writePops(delta)
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let jmp = comp.emitJump(delta, opJump)
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scope.jumps.add(jmp)
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proc endScope(comp: Compiler) =
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# remove locals
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let popped = comp.scopes.pop()
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let function = popped.function
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when debugCompiler:
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debugEcho &"End scope called for depth {comp.scopes.len} function? {function}"
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if function:
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comp.restoreInFunct(popped)
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else:
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comp.restore(popped)
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# patch jumps to after the scope (such jumps from breaks emit the pops before jumping)
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for jump in popped.jumps:
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comp.patchJump(jump)
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if function:
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comp.writeChunk(0, opReturn)
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# EXPRESSIONS
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proc parsePrecedence(comp: Compiler, prec: Precedence) =
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comp.advance()
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let rule = comp.previous.tokenType.getRule()
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if rule.prefix != nop:
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comp.canAssign = prec <= pcAssignment
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when debugCompiler:
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debugEcho &"parsePrecedence call, valid prefix op found, rule used: {rule.name}, precedence: {prec}"
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rule.prefix(comp)
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while prec <= comp.current.tokenType.getRule().prec:
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comp.advance()
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# checked for isSome in the loop
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# since advance moves current to previous
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if comp.previous.tokenType.getRule().infix == nop:
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# should never happen, as having a precedence set
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# means that it is a binary op
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comp.error("Invalid rule table.")
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return
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else:
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let infixRule = comp.previous.tokenType.getRule().infix
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infixRule(comp)
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else:
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comp.error(&"Expect expression, got {($comp.previous.tokenType)[2..^1]}.")
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proc expression(comp: Compiler) =
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## The lowest precedence among the pratt-parsed expressions
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# DO NOT ADD ANYTHING HERE
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# only use the pratt table for parsing expressions!
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when assertionsVM:
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let oldStackIndex = comp.stackIndex
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comp.parsePrecedence(pcAssignment)
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when assertionsVM:
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let diff = comp.stackIndex - oldStackIndex
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if diff != 1:
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comp.error(&"Assertion failed: expression increased ({oldStackIndex} -> {comp.stackIndex}) the stack index by {diff} (should be 1).")
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proc number(comp: Compiler) =
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# assume the number is already advanced through
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let value = comp.previous.text.parseFloat.fromFloat()
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comp.writeConstant(value)
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when debugCompiler:
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debugEcho &"Written constant (type: {value.ndType}, str repr: {$value}) to chunk"
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tkNumber.genRule(number, nop, pcNone)
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proc expFalse(comp: Compiler) =
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comp.writeChunk(1, opFalse)
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tkFalse.genRule(expFalse, nop, pcNone)
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proc expTrue(comp: Compiler) =
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comp.writeChunk(1, opTrue)
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tkTrue.genRule(expTrue, nop, pcNone)
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proc expNil(comp: Compiler) =
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comp.writeChunk(1, opNil)
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tkNil.genRule(expNil, nop, pcNone)
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proc expString(comp: Compiler) =
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let value = comp.previous.text[1..^2].fromNimString()
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comp.writeConstant(value)
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when debugCompiler:
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debugEcho &"Written constant (type: {value.ndType}, str repr: {$value}) to chunk"
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tkString.genRule(expString, nop, pcNone)
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proc resolveLocal(comp: Compiler, name: string): int =
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## returns the stack index of the local of the name
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var i = comp.locals.high
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while i >= 0:
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let local = comp.locals[i]
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if local.name == name:
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if local.depth == -1:
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comp.error("Can't read local variable in its own initializer.")
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return local.index
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i.dec
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return -1
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proc variable(comp: Compiler) =
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# named variable
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var getOp = opGetGlobal
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var setOp = opSetGlobal
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let name = comp.previous.text
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# try resolving local, set arg to the index on the stack
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var arg = comp.resolveLocal(name)
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if arg != -1:
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# local
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getOp = opGetLocal
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setOp = opSetLocal
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else:
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# global
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arg = comp.chunk.addConstant(name.fromNimString())
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if comp.match(tkEqual):
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# assignment (global/local)
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if not comp.canAssign:
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comp.error("Invalid assignment target.")
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return
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comp.expression()
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comp.writeChunk(0, setOp)
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else:
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# get (global/local)
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comp.writeChunk(1, getOp)
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comp.writeChunk(0, arg.toDU8)
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tkIdentifier.genRule(variable, nop, pcNone)
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proc grouping(comp: Compiler) =
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# assume initial '(' is already consumed
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comp.expression()
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comp.consume(tkRightParen, "Expect ')' after expression.")
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proc parseCall(comp: Compiler) =
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# ( consumed
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# create the call env
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# current stack before opCall:
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# ... <funct obj> <arg1> <arg2> <arg3>
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# opCall converts it to this
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# ... <ret val> <arg1> <arg2> <arg3>
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var argcount = 0
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# put args on stack
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while comp.current.tokenType notin {tkRightParen, tkEof}:
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comp.expression()
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inc argcount
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if comp.current.tokenType != tkRightParen:
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comp.consume(tkComma, "Expected ',' between arguments in function calls.")
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comp.consume(tkRightParen, "Expected ')' after arguments in function calls.")
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# emit call
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comp.writeChunk(-argcount, opCall)
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comp.writeChunk(0, argcount.uint8)
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tkLeftParen.genRule(grouping, parseCall, pcCall)
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proc unary(comp: Compiler) =
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let opType = comp.previous.tokenType
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comp.parsePrecedence(pcUnary)
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case opType:
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of tkMinus:
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comp.writeChunk(0, opNegate)
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of tkBang:
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comp.writeChunk(0, opNot)
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else:
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discard # unreachable
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tkBang.genRule(unary, nop, pcNone)
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proc binary(comp: Compiler) =
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let opType = comp.previous.tokenType
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# safety checked in parsePrecedence
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let rule = opType.getRule()
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comp.parsePrecedence(rule.applyRule.increment)
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case opType:
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of tkPlus:
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comp.writeChunk(-1, opAdd)
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of tkMinus:
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comp.writeChunk(-1, opSubtract)
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of tkStar:
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comp.writeChunk(-1, opMultiply)
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of tkSlash:
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comp.writeChunk(-1, opDivide)
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of tkEqualEqual:
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comp.writeChunk(-1, opEqual)
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of tkBangEqual:
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comp.writeChunk(-1, opEqual)
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comp.writeChunk(0, opNot)
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of tkGreater:
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comp.writeChunk(-1, opGreater)
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of tkLess:
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comp.writeChunk(-1, opLess)
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of tkGreaterEqual:
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comp.writeChunk(-1, opLess)
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comp.writeChunk(0, opNot)
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of tkLessEqual:
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comp.writeChunk(-1, opGreater)
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comp.writeChunk(0, opNot)
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else:
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return # unreachable
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tkMinus.genRule(unary, binary, pcTerm)
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tkPlus.genRule(nop, binary, pcTerm)
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tkSlash.genRule(nop, binary, pcFactor)
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tkStar.genRule(nop, binary, pcFactor)
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tkEqualEqual.genRule(nop, binary, pcEquality)
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tkBangEqual.genRule(nop, binary, pcEquality)
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tkGreater.genRule(nop, binary, pcComparison)
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tkGreaterEqual.genRule(nop, binary, pcComparison)
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tkLess.genRule(nop, binary, pcComparison)
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tkLessEqual.genRule(nop, binary, pcComparison)
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proc ifExpr(comp: Compiler) =
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# if expressions return the body if condition is truthy,
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# the else expression otherwise, unless there is no else:
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# if there is no else, it returns the condition if it is falsey
|
|
comp.consume(tkLeftParen, "Expect '(' after 'if'.")
|
|
comp.expression()
|
|
comp.consume(tkRightParen, "Expect ')' after condition.")
|
|
|
|
let thenJump = comp.emitJump(0, opJumpIfFalse)
|
|
|
|
# conditional code that can be jumped over must leave the stack in tact!
|
|
|
|
comp.writeChunk(-1, opPop)
|
|
comp.expression()
|
|
# net change to stack: -1 + 1 = 0
|
|
|
|
let elseJump = comp.emitJump(0, opJump)
|
|
comp.patchJump(thenJump)
|
|
|
|
if comp.match(tkElse):
|
|
comp.writeChunk(-1, opPop)
|
|
comp.expression()
|
|
|
|
comp.patchJump(elseJump)
|
|
|
|
|
|
tkIf.genRule(ifExpr, nop, pcNone)
|
|
|
|
proc andExpr(comp: Compiler) =
|
|
let endJump = comp.emitJump(0, opJumpIfFalse)
|
|
|
|
comp.writeChunk(-1, opPop)
|
|
comp.parsePrecedence(pcAnd)
|
|
# net effect on stack: -1 + 1 = 0
|
|
|
|
comp.patchJump(endJump)
|
|
|
|
tkAnd.genRule(nop, andExpr, pcAnd)
|
|
|
|
proc orExpr(comp: Compiler) =
|
|
let elseJump = comp.emitJump(0, opJumpIfFalse)
|
|
let endJump = comp.emitJump(0, opJump)
|
|
|
|
comp.patchJump(elseJump)
|
|
|
|
comp.writeChunk(-1, opPop)
|
|
comp.parsePrecedence(pcOr)
|
|
# net effect on stack: -1 + 1 = 0
|
|
|
|
comp.patchJump(endJump)
|
|
|
|
tkOr.genRule(nop, orExpr, pcOr)
|
|
|
|
proc debugExpr(comp: Compiler) =
|
|
comp.expression()
|
|
when debugCompiler:
|
|
debugEcho &"debug expression, current stackindex: {comp.stackIndex}"
|
|
comp.writeChunk(0, opPrint)
|
|
|
|
tkPrint.genRule(debugExpr, nop, pcNone)
|
|
|
|
proc parseWhile(comp: Compiler) =
|
|
|
|
comp.writeChunk(1, opNil) # return value
|
|
let loopStart = comp.chunk.len
|
|
comp.consume(tkLeftParen, "Expect '(' after 'while'.")
|
|
# condition
|
|
comp.expression()
|
|
comp.consume(tkRightParen, "Expect ')' after condition.")
|
|
|
|
let exitJump = comp.emitJump(-1, opJumpIfFalsePop)
|
|
# this cannot be handled with just opPop, since the net change in the
|
|
# stack size inside code that is conditional must be 0!
|
|
|
|
# body
|
|
comp.writeChunk(-1, opPop) # pop the old return value
|
|
comp.expression()
|
|
# net stack change: 1 + -1 = 0
|
|
|
|
comp.emitLoop(loopstart = loopStart, delta = 0, op = opLoop)
|
|
comp.patchJump(exitJump)
|
|
|
|
|
|
tkWhile.genRule(parseWhile, nop, pcNone)
|
|
|
|
proc parseFunct(comp: Compiler) =
|
|
|
|
# jump over
|
|
let jumpOverBody = comp.emitJump(1, opFunctionDef)
|
|
|
|
comp.consume(tkLeftParen, "Expected '(' after keyword 'funct'.")
|
|
|
|
var params: seq[string]
|
|
# parameters
|
|
while comp.current.tokenType == tkIdentifier:
|
|
comp.advance()
|
|
params.add(comp.previous.text)
|
|
if comp.current.tokenType == tkRightParen:
|
|
break
|
|
comp.consume(tkComma, "Expected ',' to separate items in the parameter list.")
|
|
|
|
comp.consume(tkRightParen, "Expected ')' after parameter list.")
|
|
|
|
# function body:
|
|
let functII = comp.chunk.len
|
|
comp.beginScope(function = true) # this saves the old stackindex, sets it to 0, :function and :result at index 0
|
|
# assumption:
|
|
# the caller will create the following stack for the function to run in:
|
|
# [0] = return value placeholder
|
|
# [1] = arg #1
|
|
# [2] = arg #2
|
|
# [3] = arg #3
|
|
|
|
if params.len > shortArgMax:
|
|
comp.error("Too many parameters.")
|
|
|
|
comp.writeChunk(0, opCheckArity) # runtime arity check
|
|
comp.writeChunk(0, params.len.uint8)
|
|
|
|
for i in countup(1, params.len):
|
|
comp.stackIndex = i
|
|
comp.addLocal(params[i-1], 0)
|
|
comp.expression()
|
|
when assertionsCompiler:
|
|
let shouldbeStackIndex = params.len + 1
|
|
if shouldbeStackIndex != comp.stackIndex:
|
|
comp.error(&"Assertion failed: wrong stackindex ({comp.stackIndex}) in function declaration (should be {shouldbeStackIndex}).")
|
|
comp.endScope()
|
|
dec comp.stackIndex # the previous end scope did not put anything on the stack, it is jumped over
|
|
|
|
# end of function declaration:
|
|
comp.patchJump(jumpOverBody)
|
|
|
|
tkFunct.genRule(parseFunct, nop, pcNone)
|
|
|
|
# lists
|
|
|
|
proc parseList(comp: Compiler) =
|
|
var count: int
|
|
while comp.current.tokenType != tkRightBracket:
|
|
comp.expression()
|
|
count.inc()
|
|
if comp.current.tokenType != tkRightBracket or comp.current.tokenType == tkComma:
|
|
comp.consume(tkComma, "Comma expected after list member.")
|
|
comp.consume(tkRightBracket, "Right bracket expected after list members.")
|
|
if count > argMax:
|
|
comp.error("Maximum list length exceeded.")
|
|
comp.writeChunk(1 - count, opCreateList)
|
|
comp.writeChunk(0, count.toDU8())
|
|
|
|
|
|
tkStartList.genRule(parseList, nop, pcNone)
|
|
|
|
# tables
|
|
|
|
proc parseTable(comp: Compiler) =
|
|
var count: int
|
|
while comp.current.tokenType != tkRightBrace:
|
|
comp.expression()
|
|
comp.consume(tkEqual, "Equal sign expected after key.")
|
|
comp.expression()
|
|
count.inc()
|
|
if comp.current.tokenType != tkRightBrace or comp.current.tokenType == tkComma:
|
|
comp.consume(tkComma, "Comma expected after key-value pair.")
|
|
comp.consume(tkRightBrace, "Right brace expected after list members.")
|
|
if count > argMax:
|
|
comp.error("Maximum table length exceeded.")
|
|
comp.writeChunk(1 - 2 * count, opCreateTable)
|
|
comp.writeChunk(0, count.toDU8())
|
|
|
|
tkStartTable.genRule(parseTable, nop, pcNone)
|
|
|
|
# len op
|
|
|
|
proc parseLen(comp: Compiler) =
|
|
comp.expression()
|
|
comp.writeChunk(0, opLen)
|
|
|
|
tkHashtag.genRule(parseLen, nop, pcNone)
|
|
|
|
# get/set index
|
|
|
|
proc parseIndex(comp: Compiler) =
|
|
# the index
|
|
comp.expression()
|
|
comp.consume(tkRightBracket, "Right bracket expected after index.")
|
|
if comp.match(tkEqual):
|
|
comp.expression()
|
|
comp.writeChunk(-2, opSetIndex)
|
|
else:
|
|
comp.writeChunk(-1, opGetIndex)
|
|
|
|
tkLeftBracket.genRule(nop, parseIndex, pcIndex)
|
|
|
|
# below are the expressions that can contain statements in some way
|
|
# the only expressions that can contain a statement are:
|
|
# the block expression
|
|
proc statement(comp: Compiler)
|
|
|
|
proc parseBlock(comp: Compiler) =
|
|
## Despite the name, can be used for statements if the arg statement is true
|
|
## Also can be used for function bodies
|
|
comp.beginScope()
|
|
while comp.current.tokenType != tkRightBrace and comp.current.tokenType != tkEof:
|
|
comp.statement()
|
|
comp.endScope()
|
|
|
|
comp.consume(tkRightBrace, "Expect '}' after block.")
|
|
|
|
tkLeftBrace.genRule(parseBlock, nop, pcNone)
|
|
|
|
# statements
|
|
|
|
proc parseVariable(comp: Compiler, msg: string): int =
|
|
## Parses variable declarations
|
|
## During manipulation with variables:
|
|
## if global:
|
|
## consume the identifier and return index to work with
|
|
## if local:
|
|
## register the name with the vm
|
|
comp.consume(tkIdentifier, msg)
|
|
let name = comp.previous.text
|
|
|
|
if name[0] in {':'}:
|
|
comp.error("Illegal variable name.")
|
|
|
|
if comp.scopes.len > 0: # declareVariable
|
|
# local
|
|
|
|
# check if name exists already within scope
|
|
for i in countdown(comp.locals.high, 0):
|
|
let local = comp.locals[i]
|
|
if local.depth != -1 and local.depth < comp.scopes.len:
|
|
break
|
|
|
|
if name == local.name:
|
|
comp.error("Already a variable with this name in this scope.")
|
|
break
|
|
|
|
comp.addLocal(name, 1)
|
|
0 # index to the constant is irrelevant if the var is local
|
|
else:
|
|
# global
|
|
comp.chunk.addConstant(name.fromNimString())
|
|
|
|
proc defineVariable(comp: Compiler, index: int) =
|
|
## Generate code that moves the variable on the stack
|
|
## to a variable at the right place in memory
|
|
## the right place is defined by the 3 following byte after the op
|
|
## the thing to move is the item below it
|
|
|
|
if comp.scopes.len > 0:
|
|
# local variable: it's already on the right place
|
|
# but we need to mark initialized
|
|
comp.markInitialized()
|
|
else:
|
|
comp.writeChunk(-1, opDefineGlobal)
|
|
comp.writeChunk(0, index.toDU8)
|
|
|
|
proc varStatement(comp: Compiler) =
|
|
let globalIndex = comp.parseVariable("Expect variable name.")
|
|
|
|
if comp.match(tkEqual):
|
|
comp.expression()
|
|
else:
|
|
comp.writeChunk(1, opNil)
|
|
|
|
comp.defineVariable(globalIndex)
|
|
|
|
|
|
proc breakStatement(comp: Compiler) =
|
|
if not comp.match(tkLabel):
|
|
comp.error("Label expected after break.")
|
|
|
|
let label = comp.previous.text[1..^1]
|
|
for i in countdown(comp.scopes.high, 0):
|
|
let scope = comp.scopes[i]
|
|
if scope.labels.contains(label):
|
|
comp.jumpToEnd(scope)
|
|
break
|
|
|
|
comp.consume(tkSemicolon, "Semicolon expected after break statement.")
|
|
if comp.current.tokenType != tkRightBrace:
|
|
comp.error("Break statement must be the last element inside the innermost block it is in.")
|
|
|
|
proc statement(comp: Compiler) =
|
|
if comp.match(tkVar):
|
|
comp.varStatement()
|
|
comp.consume(tkSemicolon, "Semicolon expected after expression statement.")
|
|
elif comp.match(tkBreak):
|
|
comp.breakStatement()
|
|
else:
|
|
comp.expression()
|
|
comp.writeChunk(-1, opPop)
|
|
comp.consume(tkSemicolon, "Semicolon expected after expression statement.")
|
|
|
|
if comp.panicMode:
|
|
comp.synchronize()
|
|
|
|
proc compile*(comp: Compiler) =
|
|
comp.scanner = newScanner(comp.source)
|
|
comp.writeChunk(0, opNil)
|
|
# the starting stackIndex is 0, which points to this nil
|
|
# it is correctly set to delta = 0!!!
|
|
comp.advance()
|
|
while comp.current.tokenType != tkEof:
|
|
comp.statement()
|
|
comp.writeChunk(-1, opPop)
|
|
comp.writeChunk(0, opReturn)
|
|
when debugDumpChunk:
|
|
if not comp.hadError:
|
|
comp.chunk.disassembleChunk()
|