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arf/parser/phrase.go

319 lines
8.5 KiB
Go

package parser
import "git.tebibyte.media/arf/arf/lexer"
// operatorTokens lists all symbolic tokens that can act as a command to a
// phrase.
var operatorTokens = []lexer.TokenKind {
lexer.TokenKindColon,
lexer.TokenKindPlus,
lexer.TokenKindMinus,
lexer.TokenKindIncrement,
lexer.TokenKindDecrement,
lexer.TokenKindAsterisk,
lexer.TokenKindSlash,
lexer.TokenKindExclamation,
lexer.TokenKindPercent,
lexer.TokenKindPercentAssignment,
lexer.TokenKindTilde,
lexer.TokenKindTildeAssignment,
lexer.TokenKindEqualTo,
lexer.TokenKindNotEqualTo,
lexer.TokenKindLessThanEqualTo,
lexer.TokenKindLessThan,
lexer.TokenKindLShift,
lexer.TokenKindLShiftAssignment,
lexer.TokenKindGreaterThan,
lexer.TokenKindGreaterThanEqualTo,
lexer.TokenKindRShift,
lexer.TokenKindRShiftAssignment,
lexer.TokenKindBinaryOr,
lexer.TokenKindBinaryOrAssignment,
lexer.TokenKindLogicalOr,
lexer.TokenKindBinaryAnd,
lexer.TokenKindBinaryAndAssignment,
lexer.TokenKindLogicalAnd,
lexer.TokenKindBinaryXor,
lexer.TokenKindBinaryXorAssignment,
}
// isTokenOperator returns whether or not the token is an operator token.
func isTokenOperator (token lexer.Token) (isOperator bool) {
for _, kind := range operatorTokens {
if token.Is(kind) {
isOperator = true
return
}
}
return
}
// validPhraseStartTokens lists all tokens that are expected when parsing the
// first part of a phrase.
var validPhraseStartTokens = append (
operatorTokens,
lexer.TokenKindLBracket,
lexer.TokenKindName,
lexer.TokenKindString)
// validBlockLevelPhraseTokens lists all tokens that are expected when parsing
// a block level phrase.
var validBlockLevelPhraseTokens = append (
validArgumentStartTokens,
lexer.TokenKindNewline,
lexer.TokenKindReturnDirection)
// validDelimitedPhraseTokens is like validBlockLevelPhraseTokens, but it also
// includes a right brace token.
var validDelimitedPhraseTokens = append (
validArgumentStartTokens,
lexer.TokenKindNewline,
lexer.TokenKindIndent,
lexer.TokenKindRBracket,
lexer.TokenKindReturnDirection)
// controlFlowNames contains a list of all command names that must have a block
// underneath them.
var controlFlowNames = []string {
"if", "else", "elseif",
"for", "while",
"defer",
}
// parseBlock parses an indented block of phrases
func (parser *ParsingOperation) parseBlock (
indent int,
) (
block Block,
err error,
) {
for {
// if we've left the block, stop parsing
if !parser.token.Is(lexer.TokenKindIndent) { return }
if parser.token.Value().(int) != indent { return }
var phrase Phrase
phrase, err = parser.parseBlockLevelPhrase(indent)
block = append(block, phrase)
if err != nil { return }
}
return
}
// parseBlockLevelPhrase parses a phrase that is not being used as an argument
// to something else. This method is allowed to do things like parse return
// directions, and indented blocks beneath the phrase.
func (parser *ParsingOperation) parseBlockLevelPhrase (
indent int,
) (
phrase Phrase,
err error,
) {
if !parser.token.Is(lexer.TokenKindIndent) { return }
if parser.token.Value().(int) != indent { return }
err = parser.nextToken(validPhraseStartTokens...)
if err != nil { return }
expectRightBracket := false
if parser.token.Is(lexer.TokenKindLBracket) {
expectRightBracket = true
err = parser.nextToken()
if err != nil { return }
}
// get command
err = parser.expect(validPhraseStartTokens...)
if err != nil { return }
if isTokenOperator(parser.token) {
phrase.command, err = parser.parseOperatorArgument()
if err != nil { return }
} else {
phrase.command, err = parser.parseArgument()
if err != nil { return }
}
for {
if expectRightBracket {
// delimited
// [someFunc arg1 arg2 arg3] -> someVariable
err = parser.expect(validDelimitedPhraseTokens...)
if err != nil { return }
if parser.token.Is(lexer.TokenKindRBracket) {
// this is an ending delimiter
err = parser.nextToken()
if err != nil { return }
break
} else if parser.token.Is(lexer.TokenKindNewline) {
// we are delimited, so we can safely skip
// newlines
err = parser.nextToken()
if err != nil { return }
continue
} else if parser.token.Is(lexer.TokenKindIndent) {
// we are delimited, so we can safely skip
// indents
err = parser.nextToken()
if err != nil { return }
continue
}
} else {
// not delimited
// someFunc arg1 arg2 arg3 -> someVariable
err = parser.expect(validBlockLevelPhraseTokens...)
if err != nil { return }
if parser.token.Is(lexer.TokenKindReturnDirection) {
// we've reached a return direction, so that
// means this is the end of the phrase
break
} else if parser.token.Is(lexer.TokenKindNewline) {
// we've reached the end of the line, so that
// means this is the end of the phrase.
break
}
}
// this is an argument
var argument Argument
argument, err = parser.parseArgument()
phrase.arguments = append(phrase.arguments, argument)
}
// expect newline or return direction
err = parser.expect (
lexer.TokenKindNewline,
lexer.TokenKindReturnDirection)
if err != nil { return }
expectReturnDirection := parser.token.Is(lexer.TokenKindReturnDirection)
// if we have hit a return direction, parse it...
if expectReturnDirection {
err = parser.nextToken()
if err != nil { return }
for {
err = parser.expect (
lexer.TokenKindNewline,
lexer.TokenKindName)
if err != nil { return }
// ...until we hit a newline
if parser.token.Is(lexer.TokenKindNewline) { break }
var returnTo Argument
returnTo, err = parser.parseArgument()
if err != nil { return }
phrase.returnsTo = append(phrase.returnsTo, returnTo)
}
}
err = parser.nextToken()
if err != nil { return }
// if this is a control flow statement, parse block under it
if phrase.command.kind == ArgumentKindIdentifier {
// perhaps it is a normal control flow statement?
command := phrase.command.value.(Identifier)
if len(command.trail) != 1 { return }
isControlFlow := false
for _, name := range controlFlowNames {
if command.trail[0] == name {
isControlFlow = true
break
}
}
if !isControlFlow { return }
} else if phrase.command.kind == ArgumentKindOperator {
// perhaps it is a switch case?
command := phrase.command.value.(lexer.TokenKind)
if command != lexer.TokenKindColon { return }
} else {
return
}
// if it is any of those, parse the block under it
phrase.block, err = parser.parseBlock(indent + 1)
return
}
// parseArgumentLevelPhrase parses a phrase that is being used as an argument to
// something. It is forbidden from using return direction, and it must be
// delimited by brackets.
func (parser *ParsingOperation) parseArgumentLevelPhrase () (
phrase Phrase,
err error,
) {
err = parser.expect(lexer.TokenKindLBracket)
if err != nil { return }
// get command
err = parser.nextToken(validPhraseStartTokens...)
if err != nil { return }
if isTokenOperator(parser.token) {
phrase.command, err = parser.parseOperatorArgument()
if err != nil { return }
} else {
phrase.command, err = parser.parseArgument()
if err != nil { return }
}
for {
// delimited
// [someFunc arg1 arg2 arg3] -> someVariable
err = parser.expect(validDelimitedPhraseTokens...)
if err != nil { return }
if parser.token.Is(lexer.TokenKindRBracket) {
// this is an ending delimiter
err = parser.nextToken()
if err != nil { return }
return
} else if parser.token.Is(lexer.TokenKindNewline) {
// we are delimited, so we can safely skip
// newlines
err = parser.nextToken()
if err != nil { return }
continue
} else if parser.token.Is(lexer.TokenKindIndent) {
// we are delimited, so we can safely skip
// indents
err = parser.nextToken()
if err != nil { return }
continue
}
// this is an argument
var argument Argument
argument, err = parser.parseArgument()
phrase.arguments = append(phrase.arguments, argument)
}
}
// parseOperatorArgument parses an operator argument. This is only used to parse
// operator phrase commands.
func (parser *ParsingOperation) parseOperatorArgument () (
operator Argument,
err error,
) {
err = parser.expect(operatorTokens...)
if err != nil { return }
operator.location = parser.token.Location()
operator.kind = ArgumentKindOperator
operator.value = parser.token.Kind()
err = parser.nextToken()
return
}