--- name: "me_cpucore" section: "3tcl" platform: "linux" package: "tcllib" version: "2.0+dfsg-4" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/me_cpucore" --- # me\_cpucore(3tcl) ME virtual machine state manipulation ``` ``` ## NAME grammar::me::cpu::core - ME virtual machine state manipulation ## SYNOPSIS package require **Tcl 8.5 9** package require **grammar::me::cpu::core ?0.4?** **::grammar::me::cpu::core** **disasm** *asm* **::grammar::me::cpu::core** **asm** *asm* **::grammar::me::cpu::core** **new** *asm* **::grammar::me::cpu::core** **lc** *state* *location* **::grammar::me::cpu::core** **tok** *state* ?*from* ?*to*?? **::grammar::me::cpu::core** **pc** *state* **::grammar::me::cpu::core** **iseof** *state* **::grammar::me::cpu::core** **at** *state* **::grammar::me::cpu::core** **cc** *state* **::grammar::me::cpu::core** **sv** *state* **::grammar::me::cpu::core** **ok** *state* **::grammar::me::cpu::core** **error** *state* **::grammar::me::cpu::core** **lstk** *state* **::grammar::me::cpu::core** **astk** *state* **::grammar::me::cpu::core** **mstk** *state* **::grammar::me::cpu::core** **estk** *state* **::grammar::me::cpu::core** **rstk** *state* **::grammar::me::cpu::core** **nc** *state* **::grammar::me::cpu::core** **ast** *state* **::grammar::me::cpu::core** **halted** *state* **::grammar::me::cpu::core** **code** *state* **::grammar::me::cpu::core** **eof** *statevar* **::grammar::me::cpu::core** **put** *statevar* *tok* *lex* *line* *col* **::grammar::me::cpu::core** **run** *statevar* ?*n*? ``` ``` ## DESCRIPTION This package provides an implementation of the ME virtual machine. Please go and read the document **grammar::me\_intro** first if you do not know what a ME virtual machine is. This implementation represents each ME virtual machine as a Tcl value and provides commands to manipulate and query such values to show the effects of executing instructions, adding tokens, retrieving state, etc. The values fully follow the paradigm of Tcl that every value is a string and while also allowing C implementations for a proper Tcl\_ObjType to keep all the important data in native data structures. Because of the latter it is recommended to access the state values *only* through the commands of this package to ensure that internal representation is not shimmered away. The actual structure used by all state values is described in section **CPU STATE**. ## API The package directly provides only a single command, and all the functionality is made available through its methods. - **::grammar::me::cpu::core** **disasm** *asm* This method returns a list containing a disassembly of the match instructions in *asm*. The format of *asm* is specified in the section **MATCH PROGRAM REPRESENTATION**. Each element of the result contains instruction label, instruction name, and the instruction arguments, in this order. The label can be the empty string. Jump destinations are shown as labels, strings and tokens unencoded. Token names are prefixed with their numeric id, if, and only if a tokmap is defined. The two components are separated by a colon. - **::grammar::me::cpu::core** **asm** *asm* This method returns code in the format as specified in section **MATCH PROGRAM REPRESENTATION** generated from ME assembly code *asm*, which is in the format as returned by the method **disasm**. - **::grammar::me::cpu::core** **new** *asm* This method creates state value for a ME virtual machine in its initial state and returns it as its result. The argument *matchcode* contains a Tcl representation of the match instructions the machine has to execute while parsing the input stream. Its format is specified in the section **MATCH PROGRAM REPRESENTATION**. The *tokmap* argument taken by the implementation provided by the package **grammar::me::tcl** is here hidden inside of the match instructions and therefore not needed. - **::grammar::me::cpu::core** **lc** *state* *location* This method takes the state value of a ME virtual machine and uses it to convert a location in the input stream (as offset) into a line number and column index. The result of the method is a 2-element list containing the two pieces in the order mentioned in the previous sentence. *Note* that the method cannot convert locations which the machine has not yet read from the input stream. In other words, if the machine has read 7 characters so far it is possible to convert the offsets **0** to **6**, but nothing beyond that. This also shows that it is not possible to convert offsets which refer to locations before the beginning of the stream. This utility allows higher levels to convert the location offsets found in the error status and the AST into more human readable data. - **::grammar::me::cpu::core** **tok** *state* ?*from* ?*to*?? This method takes the state value of a ME virtual machine and returns a Tcl list containing the part of the input stream between the locations *from* and *to* (both inclusive). If *to* is not specified it will default to the value of *from*. If *from* is not specified either the whole input stream is returned. This method places the same restrictions on its location arguments as the method **lc**. - **::grammar::me::cpu::core** **pc** *state* This method takes the state value of a ME virtual machine and returns the current value of the stored program counter. - **::grammar::me::cpu::core** **iseof** *state* This method takes the state value of a ME virtual machine and returns the current value of the stored eof flag. - **::grammar::me::cpu::core** **at** *state* This method takes the state value of a ME virtual machine and returns the current location in the input stream. - **::grammar::me::cpu::core** **cc** *state* This method takes the state value of a ME virtual machine and returns the current token. - **::grammar::me::cpu::core** **sv** *state* This method takes the state value of a ME virtual machine and returns the current semantic value stored in it. This is an abstract syntax tree as specified in the document **grammar::me\_ast**, section **AST VALUES**. - **::grammar::me::cpu::core** **ok** *state* This method takes the state value of a ME virtual machine and returns the match status stored in it. - **::grammar::me::cpu::core** **error** *state* This method takes the state value of a ME virtual machine and returns the current error status stored in it. - **::grammar::me::cpu::core** **lstk** *state* This method takes the state value of a ME virtual machine and returns the location stack. - **::grammar::me::cpu::core** **astk** *state* This method takes the state value of a ME virtual machine and returns the AST stack. - **::grammar::me::cpu::core** **mstk** *state* This method takes the state value of a ME virtual machine and returns the AST marker stack. - **::grammar::me::cpu::core** **estk** *state* This method takes the state value of a ME virtual machine and returns the error stack. - **::grammar::me::cpu::core** **rstk** *state* This method takes the state value of a ME virtual machine and returns the subroutine return stack. - **::grammar::me::cpu::core** **nc** *state* This method takes the state value of a ME virtual machine and returns the nonterminal match cache as a dictionary. - **::grammar::me::cpu::core** **ast** *state* This method takes the state value of a ME virtual machine and returns the abstract syntax tree currently at the top of the AST stack stored in it. This is an abstract syntax tree as specified in the document **grammar::me\_ast**, section **AST VALUES**. - **::grammar::me::cpu::core** **halted** *state* This method takes the state value of a ME virtual machine and returns the current halt status stored in it, i.e. if the machine has stopped or not. - **::grammar::me::cpu::core** **code** *state* This method takes the state value of a ME virtual machine and returns the code stored in it, i.e. the instructions executed by the machine. - **::grammar::me::cpu::core** **eof** *statevar* This method takes the state value of a ME virtual machine as stored in the variable named by *statevar* and modifies it so that the eof flag inside is set. This signals to the machine that whatever token are in the input queue are the last to be processed. There will be no more. - **::grammar::me::cpu::core** **put** *statevar* *tok* *lex* *line* *col* This method takes the state value of a ME virtual machine as stored in the variable named by *statevar* and modifies it so that the token *tok* is added to the end of the input queue, with associated lexeme data *lex* and *line*/*col*umn information. The operation will fail with an error if the eof flag of the machine has been set through the method **eof**. - **::grammar::me::cpu::core** **run** *statevar* ?*n*? This method takes the state value of a ME virtual machine as stored in the variable named by *statevar*, executes a number of instructions and stores the state resulting from their modifications back into the variable. The execution loop will run until either - • *n* instructions have been executed, or - • a halt instruction was executed, or - • the input queue is empty and the code is asking for more tokens to process. If no limit *n* was set only the last two conditions are checked for. ### MATCH PROGRAM REPRESENTATION A match program is represented by nested Tcl list. The first element, *asm*, is a list of integer numbers, the instructions to execute, and their arguments. The second element, *pool*, is a list of strings, referenced by the instructions, for error messages, token names, etc. The third element, *tokmap*, provides ordering information for the tokens, mapping their names to their numerical rank. This element can be empty, forcing lexicographic comparison when matching ranges. All ME instructions are encoded as integer numbers, with the mapping given below. A number of the instructions, those which handle error messages, have been given an additional argument to supply that message explicitly instead of having it constructed from token names, etc. This allows the machine state to store only the message ids instead of the full strings. Jump destination arguments are absolute indices into the *asm* element, refering to the instruction to jump to. Any string arguments are absolute indices into the *pool* element. Tokens, characters, messages, and token (actually character) classes to match are coded as references into the *pool* as well. - \[1\] "**ict\_advance** *message*" - \[2\] "**ict\_match\_token** *tok* *message*" - \[3\] "**ict\_match\_tokrange** *tokbegin* *tokend* *message*" - \[4\] "**ict\_match\_tokclass** *code* *message*" - \[5\] "**inc\_restore** *branchlabel* *nt*" - \[6\] "**inc\_save** *nt*" - \[7\] "**icf\_ntcall** *branchlabel*" - \[8\] "**icf\_ntreturn**" - \[9\] "**iok\_ok**" - \[10\] "**iok\_fail**" - \[11\] "**iok\_negate**" - \[12\] "**icf\_jalways** *branchlabel*" - \[13\] "**icf\_jok** *branchlabel*" - \[14\] "**icf\_jfail** *branchlabel*" - \[15\] "**icf\_halt**" - \[16\] "**icl\_push**" - \[17\] "**icl\_rewind**" - \[18\] "**icl\_pop**" - \[19\] "**ier\_push**" - \[20\] "**ier\_clear**" - \[21\] "**ier\_nonterminal** *message*" - \[22\] "**ier\_merge**" - \[23\] "**isv\_clear**" - \[24\] "**isv\_terminal**" - \[25\] "**isv\_nonterminal\_leaf** *nt*" - \[26\] "**isv\_nonterminal\_range** *nt*" - \[27\] "**isv\_nonterminal\_reduce** *nt*" - \[28\] "**ias\_push**" - \[29\] "**ias\_mark**" - \[30\] "**ias\_mrewind**" - \[31\] "**ias\_mpop**" ## CPU STATE A state value is a list containing the following elements, in the order listed below: - \[1\] *code*: Match instructions, see **MATCH PROGRAM REPRESENTATION**. - \[2\] *pc*: Program counter, *int*. - \[3\] *halt*: Halt flag, *boolean*. - \[4\] *eof*: Eof flag, *boolean* - \[5\] *tc*: Terminal cache, and input queue. Structure see below. - \[6\] *cl*: Current location, *int*. - \[7\] *ct*: Current token, *string*. - \[8\] *ok*: Match status, *boolean*. - \[9\] *sv*: Semantic value, *list*. - \[10\] *er*: Error status, *list*. - \[11\] *ls*: Location stack, *list*. - \[12\] *as*: AST stack, *list*. - \[13\] *ms*: AST marker stack, *list*. - \[14\] *es*: Error stack, *list*. - \[15\] *rs*: Return stack, *list*. - \[16\] *nc*: Nonterminal cache, *dictionary*. *tc*, the input queue of tokens waiting for processing and the terminal cache containing the tokens already processing are one unified data structure simply holding all tokens and their information, with the current location separating that which has been processed from that which is waiting. Each element of the queue/cache is a list containing the token, its lexeme information, line number, and column index, in this order. All stacks have their top element aat the end, i.e. pushing an item is equivalent to appending to the list representing the stack, and popping it removes the last element. *er*, the error status is either empty or a list of two elements, a location in the input, and a list of messages, encoded as references into the *pool* element of the *code*. *nc*, the nonterminal cache is keyed by nonterminal name and location, each value a four-element list containing current location, match status, semantic value, and error status, in this order. ## BUGS, IDEAS, FEEDBACK This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category *grammar\_me* of the *Tcllib Trackers* \[http://core.tcl.tk/tcllib/reportlist\]. Please also report any ideas for enhancements you may have for either package and/or documentation. When proposing code changes, please provide *unified diffs*, i.e the output of **diff -u**. Note further that *attachments* are strongly preferred over inlined patches. Attachments can be made by going to the **Edit** form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar. ## KEYWORDS grammar, parsing, virtual machine ## CATEGORY Grammars and finite automata ## COPYRIGHT ``` Copyright (c) 2005-2006 Andreas Kupries ```