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| 78 | .ie !"\\$4"" .TP \\$4 |
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| 106 | .. |
| 107 | .AS Tcl_Interp Tcl_CreateInterp in/out |
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| 133 | \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' |
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| 177 | .\} |
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| 179 | .nr ^x \\n(^tu+1v-\\n(^Yu |
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| 207 | .SH "STANDARD OPTIONS" |
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| 225 | Command-Line Name: \\fB\\$1\\fR |
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| 243 | \\$1\l'|0\(ul'\\$2 |
| 244 | .. |
| 245 | .TH Tcl_ParseCommand 3 8.3 Tcl "Tcl Library Procedures" |
| 246 | .BS |
| 247 | .SH NAME |
| 248 | Tcl_ParseCommand, Tcl_ParseExpr, Tcl_ParseBraces, Tcl_ParseQuotedString, Tcl_ParseVarName, Tcl_ParseVar, Tcl_FreeParse, Tcl_EvalTokens, Tcl_EvalTokensStandard \- parse Tcl scripts and expressions |
| 249 | .SH SYNOPSIS |
| 250 | .nf |
| 251 | \fB#include <tcl.h>\fR |
| 252 | .sp |
| 253 | int |
| 254 | \fBTcl_ParseCommand\fR(\fIinterp, string, numBytes, nested, parsePtr\fR) |
| 255 | .sp |
| 256 | int |
| 257 | \fBTcl_ParseExpr\fR(\fIinterp, string, numBytes, parsePtr\fR) |
| 258 | .sp |
| 259 | int |
| 260 | \fBTcl_ParseBraces\fR(\fIinterp, string, numBytes, parsePtr, append, termPtr\fR) |
| 261 | .sp |
| 262 | int |
| 263 | \fBTcl_ParseQuotedString\fR(\fIinterp, string, numBytes, parsePtr, append, termPtr\fR) |
| 264 | .sp |
| 265 | int |
| 266 | \fBTcl_ParseVarName\fR(\fIinterp, string, numBytes, parsePtr, append\fR) |
| 267 | .sp |
| 268 | CONST char * |
| 269 | \fBTcl_ParseVar\fR(\fIinterp, string, termPtr\fR) |
| 270 | .sp |
| 271 | \fBTcl_FreeParse\fR(\fIusedParsePtr\fR) |
| 272 | .sp |
| 273 | Tcl_Obj * |
| 274 | \fBTcl_EvalTokens\fR(\fIinterp, tokenPtr, numTokens\fR) |
| 275 | .sp |
| 276 | int |
| 277 | \fBTcl_EvalTokensStandard\fR(\fIinterp, tokenPtr, numTokens\fR) |
| 278 | .SH ARGUMENTS |
| 279 | .AS Tcl_Interp *usedParsePtr |
| 280 | .AP Tcl_Interp *interp out |
| 281 | For procedures other than \fBTcl_FreeParse\fR, \fBTcl_EvalTokens\fR |
| 282 | and \fBTcl_EvalTokensStandard\fR, used only for error reporting; |
| 283 | if NULL, then no error messages are left after errors. |
| 284 | For \fBTcl_EvalTokens\fR and \fBTcl_EvalTokensStandard\fR, |
| 285 | determines the context for evaluating the |
| 286 | script and also is used for error reporting; must not be NULL. |
| 287 | .AP "CONST char" *string in |
| 288 | Pointer to first character in string to parse. |
| 289 | .AP int numBytes in |
| 290 | Number of bytes in \fIstring\fR, not including any terminating null |
| 291 | character. If less than 0 then the script consists of all characters |
| 292 | in \fIstring\fR up to the first null character. |
| 293 | .AP int nested in |
| 294 | Non-zero means that the script is part of a command substitution so an |
| 295 | unquoted close bracket should be treated as a command terminator. If zero, |
| 296 | close brackets have no special meaning. |
| 297 | .AP int append in |
| 298 | Non-zero means that \fI*parsePtr\fR already contains valid tokens; the new |
| 299 | tokens should be appended to those already present. Zero means that |
| 300 | \fI*parsePtr\fR is uninitialized; any information in it is ignored. |
| 301 | This argument is normally 0. |
| 302 | .AP Tcl_Parse *parsePtr out |
| 303 | Points to structure to fill in with information about the parsed |
| 304 | command, expression, variable name, etc. |
| 305 | Any previous information in this structure |
| 306 | is ignored, unless \fIappend\fR is non-zero in a call to |
| 307 | \fBTcl_ParseBraces\fR, \fBTcl_ParseQuotedString\fR, |
| 308 | or \fBTcl_ParseVarName\fR. |
| 309 | .AP "CONST char" **termPtr out |
| 310 | If not NULL, points to a location where |
| 311 | \fBTcl_ParseBraces\fR, \fBTcl_ParseQuotedString\fR, and |
| 312 | \fBTcl_ParseVar\fR will store a pointer to the character |
| 313 | just after the terminating character (the close-brace, the last |
| 314 | character of the variable name, or the close-quote (respectively)) |
| 315 | if the parse was successful. |
| 316 | .AP Tcl_Parse *usedParsePtr in |
| 317 | Points to structure that was filled in by a previous call to |
| 318 | \fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseVarName\fR, etc. |
| 319 | .BE |
| 320 | |
| 321 | .SH DESCRIPTION |
| 322 | .PP |
| 323 | These procedures parse Tcl commands or portions of Tcl commands such as |
| 324 | expressions or references to variables. |
| 325 | Each procedure takes a pointer to a script (or portion thereof) |
| 326 | and fills in the structure pointed to by \fIparsePtr\fR |
| 327 | with a collection of tokens describing the information that was parsed. |
| 328 | The procedures normally return \fBTCL_OK\fR. |
| 329 | However, if an error occurs then they return \fBTCL_ERROR\fR, |
| 330 | leave an error message in \fIinterp's\fR result |
| 331 | (if \fIinterp\fR is not NULL), |
| 332 | and leave nothing in \fIparsePtr\fR. |
| 333 | .PP |
| 334 | \fBTcl_ParseCommand\fR is a procedure that parses Tcl |
| 335 | scripts. Given a pointer to a script, it |
| 336 | parses the first command from the script. If the command was parsed |
| 337 | successfully, \fBTcl_ParseCommand\fR returns \fBTCL_OK\fR and fills in the |
| 338 | structure pointed to by \fIparsePtr\fR with information about the |
| 339 | structure of the command (see below for details). |
| 340 | If an error occurred in parsing the command then |
| 341 | \fBTCL_ERROR\fR is returned, an error message is left in \fIinterp\fR's |
| 342 | result, and no information is left at \fI*parsePtr\fR. |
| 343 | .PP |
| 344 | \fBTcl_ParseExpr\fR parses Tcl expressions. |
| 345 | Given a pointer to a script containing an expression, |
| 346 | \fBTcl_ParseCommand\fR parses the expression. |
| 347 | If the expression was parsed successfully, |
| 348 | \fBTcl_ParseExpr\fR returns \fBTCL_OK\fR and fills in the |
| 349 | structure pointed to by \fIparsePtr\fR with information about the |
| 350 | structure of the expression (see below for details). |
| 351 | If an error occurred in parsing the command then |
| 352 | \fBTCL_ERROR\fR is returned, an error message is left in \fIinterp\fR's |
| 353 | result, and no information is left at \fI*parsePtr\fR. |
| 354 | .PP |
| 355 | \fBTcl_ParseBraces\fR parses a string or command argument |
| 356 | enclosed in braces such as |
| 357 | \fB{hello}\fR or \fB{string \\t with \\t tabs}\fR |
| 358 | from the beginning of its argument \fIstring\fR. |
| 359 | The first character of \fIstring\fR must be \fB{\fR. |
| 360 | If the braced string was parsed successfully, |
| 361 | \fBTcl_ParseBraces\fR returns \fBTCL_OK\fR, |
| 362 | fills in the structure pointed to by \fIparsePtr\fR |
| 363 | with information about the structure of the string |
| 364 | (see below for details), |
| 365 | and stores a pointer to the character just after the terminating \fB}\fR |
| 366 | in the location given by \fI*termPtr\fR. |
| 367 | If an error occurs while parsing the string |
| 368 | then \fBTCL_ERROR\fR is returned, |
| 369 | an error message is left in \fIinterp\fR's result, |
| 370 | and no information is left at \fI*parsePtr\fR or \fI*termPtr\fR. |
| 371 | .PP |
| 372 | \fBTcl_ParseQuotedString\fR parses a double-quoted string such as |
| 373 | \fB"sum is [expr $a+$b]"\fR |
| 374 | from the beginning of the argument \fIstring\fR. |
| 375 | The first character of \fIstring\fR must be \fB"\fR. |
| 376 | If the double-quoted string was parsed successfully, |
| 377 | \fBTcl_ParseQuotedString\fR returns \fBTCL_OK\fR, |
| 378 | fills in the structure pointed to by \fIparsePtr\fR |
| 379 | with information about the structure of the string |
| 380 | (see below for details), |
| 381 | and stores a pointer to the character just after the terminating \fB"\fR |
| 382 | in the location given by \fI*termPtr\fR. |
| 383 | If an error occurs while parsing the string |
| 384 | then \fBTCL_ERROR\fR is returned, |
| 385 | an error message is left in \fIinterp\fR's result, |
| 386 | and no information is left at \fI*parsePtr\fR or \fI*termPtr\fR. |
| 387 | .PP |
| 388 | \fBTcl_ParseVarName\fR parses a Tcl variable reference such as |
| 389 | \fB$abc\fR or \fB$x([expr $index + 1])\fR from the beginning of its |
| 390 | \fIstring\fR argument. |
| 391 | The first character of \fIstring\fR must be \fB$\fR. |
| 392 | If a variable name was parsed successfully, \fBTcl_ParseVarName\fR |
| 393 | returns \fBTCL_OK\fR and fills in the structure pointed to by |
| 394 | \fIparsePtr\fR with information about the structure of the variable name |
| 395 | (see below for details). If an error |
| 396 | occurs while parsing the command then \fBTCL_ERROR\fR is returned, an |
| 397 | error message is left in \fIinterp\fR's result (if \fIinterp\fR isn't |
| 398 | NULL), and no information is left at \fI*parsePtr\fR. |
| 399 | .PP |
| 400 | \fBTcl_ParseVar\fR parse a Tcl variable reference such as \fB$abc\fR |
| 401 | or \fB$x([expr $index + 1])\fR from the beginning of its \fIstring\fR |
| 402 | argument. The first character of \fIstring\fR must be \fB$\fR. If |
| 403 | the variable name is parsed successfully, \fBTcl_ParseVar\fR returns a |
| 404 | pointer to the string value of the variable. If an error occurs while |
| 405 | parsing, then NULL is returned and an error message is left in |
| 406 | \fIinterp\fR's result. |
| 407 | .PP |
| 408 | The information left at \fI*parsePtr\fR |
| 409 | by \fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, |
| 410 | \fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR |
| 411 | may include dynamically allocated memory. |
| 412 | If these five parsing procedures return \fBTCL_OK\fR |
| 413 | then the caller must invoke \fBTcl_FreeParse\fR to release |
| 414 | the storage at \fI*parsePtr\fR. |
| 415 | These procedures ignore any existing information in |
| 416 | \fI*parsePtr\fR (unless \fIappend\fR is non-zero), |
| 417 | so if repeated calls are being made to any of them |
| 418 | then \fBTcl_FreeParse\fR must be invoked once after each call. |
| 419 | .PP |
| 420 | \fBTcl_EvalTokensStandard\fR evaluates a sequence of parse tokens from |
| 421 | a Tcl_Parse structure. The tokens typically consist |
| 422 | of all the tokens in a word or all the tokens that make up the index for |
| 423 | a reference to an array variable. \fBTcl_EvalTokensStandard\fR performs the |
| 424 | substitutions requested by the tokens and concatenates the |
| 425 | resulting values. |
| 426 | The return value from \fBTcl_EvalTokensStandard\fR is a Tcl completion |
| 427 | code with one of the values \fBTCL_OK\fR, \fBTCL_ERROR\fR, |
| 428 | \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or \fBTCL_CONTINUE\fR, or possibly |
| 429 | some other integer value originating in an extension. |
| 430 | In addition, a result value or error message is left in \fIinterp\fR's |
| 431 | result; it can be retrieved using \fBTcl_GetObjResult\fR. |
| 432 | .PP |
| 433 | \fBTcl_EvalTokens\fR differs from \fBTcl_EvalTokensStandard\fR only in |
| 434 | the return convention used: it returns the result in a new Tcl_Obj. |
| 435 | The reference count of the object returned as result has been |
| 436 | incremented, so the caller must |
| 437 | invoke \fBTcl_DecrRefCount\fR when it is finished with the object. |
| 438 | If an error or other exception occurs while evaluating the tokens |
| 439 | (such as a reference to a non-existent variable) then the return value |
| 440 | is NULL and an error message is left in \fIinterp\fR's result. The use |
| 441 | of \fBTcl_EvalTokens\fR is deprecated. |
| 442 | |
| 443 | .SH "TCL_PARSE STRUCTURE" |
| 444 | .PP |
| 445 | \fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, |
| 446 | \fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR |
| 447 | return parse information in two data structures, Tcl_Parse and Tcl_Token: |
| 448 | .CS |
| 449 | typedef struct Tcl_Parse { |
| 450 | CONST char *\fIcommentStart\fR; |
| 451 | int \fIcommentSize\fR; |
| 452 | CONST char *\fIcommandStart\fR; |
| 453 | int \fIcommandSize\fR; |
| 454 | int \fInumWords\fR; |
| 455 | Tcl_Token *\fItokenPtr\fR; |
| 456 | int \fInumTokens\fR; |
| 457 | ... |
| 458 | } Tcl_Parse; |
| 459 | |
| 460 | typedef struct Tcl_Token { |
| 461 | int \fItype\fR; |
| 462 | CONST char *\fIstart\fR; |
| 463 | int \fIsize\fR; |
| 464 | int \fInumComponents\fR; |
| 465 | } Tcl_Token; |
| 466 | .CE |
| 467 | .PP |
| 468 | The first five fields of a Tcl_Parse structure |
| 469 | are filled in only by \fBTcl_ParseCommand\fR. |
| 470 | These fields are not used by the other parsing procedures. |
| 471 | .PP |
| 472 | \fBTcl_ParseCommand\fR fills in a Tcl_Parse structure |
| 473 | with information that describes one Tcl command and any comments that |
| 474 | precede the command. |
| 475 | If there are comments, |
| 476 | the \fIcommentStart\fR field points to the \fB#\fR character that begins |
| 477 | the first comment and \fIcommentSize\fR indicates the number of bytes |
| 478 | in all of the comments preceding the command, including the newline |
| 479 | character that terminates the last comment. |
| 480 | If the command is not preceded by any comments, \fIcommentSize\fR is 0. |
| 481 | \fBTcl_ParseCommand\fR also sets the \fIcommandStart\fR field |
| 482 | to point to the first character of the first |
| 483 | word in the command (skipping any comments and leading space) and |
| 484 | \fIcommandSize\fR gives the total number of bytes in the command, |
| 485 | including the character pointed to by \fIcommandStart\fR up to and |
| 486 | including the newline, close bracket, or semicolon character that |
| 487 | terminates the command. The \fInumWords\fR field gives the |
| 488 | total number of words in the command. |
| 489 | .PP |
| 490 | All parsing procedures set the remaining fields, |
| 491 | \fItokenPtr\fR and \fInumTokens\fR. |
| 492 | The \fItokenPtr\fR field points to the first in an array of Tcl_Token |
| 493 | structures that describe the components of the entity being parsed. |
| 494 | The \fInumTokens\fR field gives the total number of tokens |
| 495 | present in the array. |
| 496 | Each token contains four fields. |
| 497 | The \fItype\fR field selects one of several token types |
| 498 | that are described below. The \fIstart\fR field |
| 499 | points to the first character in the token and the \fIsize\fR field |
| 500 | gives the total number of characters in the token. Some token types, |
| 501 | such as \fBTCL_TOKEN_WORD\fR and \fBTCL_TOKEN_VARIABLE\fR, consist of |
| 502 | several component tokens, which immediately follow the parent token; |
| 503 | the \fInumComponents\fR field describes how many of these there are. |
| 504 | The \fItype\fR field has one of the following values: |
| 505 | .TP 20 |
| 506 | \fBTCL_TOKEN_WORD\fR |
| 507 | This token ordinarily describes one word of a command |
| 508 | but it may also describe a quoted or braced string in an expression. |
| 509 | The token describes a component of the script that is |
| 510 | the result of concatenating together a sequence of subcomponents, |
| 511 | each described by a separate subtoken. |
| 512 | The token starts with the first non-blank |
| 513 | character of the component (which may be a double-quote or open brace) |
| 514 | and includes all characters in the component up to but not including the |
| 515 | space, semicolon, close bracket, close quote, or close brace that |
| 516 | terminates the component. The \fInumComponents\fR field counts the total |
| 517 | number of sub-tokens that make up the word, including sub-tokens |
| 518 | of \fBTCL_TOKEN_VARIABLE\fR and \fBTCL_TOKEN_BS\fR tokens. |
| 519 | .TP |
| 520 | \fBTCL_TOKEN_SIMPLE_WORD\fR |
| 521 | This token has the same meaning as \fBTCL_TOKEN_WORD\fR, except that |
| 522 | the word is guaranteed to consist of a single \fBTCL_TOKEN_TEXT\fR |
| 523 | sub-token. The \fInumComponents\fR field is always 1. |
| 524 | .TP |
| 525 | \fBTCL_TOKEN_TEXT\fR |
| 526 | The token describes a range of literal text that is part of a word. |
| 527 | The \fInumComponents\fR field is always 0. |
| 528 | .TP |
| 529 | \fBTCL_TOKEN_BS\fR |
| 530 | The token describes a backslash sequence such as \fB\en\fR or \fB\e0xa3\fR. |
| 531 | The \fInumComponents\fR field is always 0. |
| 532 | .TP |
| 533 | \fBTCL_TOKEN_COMMAND\fR |
| 534 | The token describes a command whose result result must be substituted into |
| 535 | the word. The token includes the square brackets that surround the |
| 536 | command. The \fInumComponents\fR field is always 0 (the nested command |
| 537 | is not parsed; call \fBTcl_ParseCommand\fR recursively if you want to |
| 538 | see its tokens). |
| 539 | .TP |
| 540 | \fBTCL_TOKEN_VARIABLE\fR |
| 541 | The token describes a variable substitution, including the |
| 542 | \fB$\fR, variable name, and array index (if there is one) up through the |
| 543 | close parenthesis that terminates the index. This token is followed |
| 544 | by one or more additional tokens that describe the variable name and |
| 545 | array index. If \fInumComponents\fR is 1 then the variable is a |
| 546 | scalar and the next token is a \fBTCL_TOKEN_TEXT\fR token that gives the |
| 547 | variable name. If \fInumComponents\fR is greater than 1 then the |
| 548 | variable is an array: the first sub-token is a \fBTCL_TOKEN_TEXT\fR |
| 549 | token giving the array name and the remaining sub-tokens are |
| 550 | \fBTCL_TOKEN_TEXT\fR, \fBTCL_TOKEN_BS\fR, \fBTCL_TOKEN_COMMAND\fR, and |
| 551 | \fBTCL_TOKEN_VARIABLE\fR tokens that must be concatenated to produce the |
| 552 | array index. The \fInumComponents\fR field includes nested sub-tokens |
| 553 | that are part of \fBTCL_TOKEN_VARIABLE\fR tokens in the array index. |
| 554 | .TP |
| 555 | \fBTCL_TOKEN_SUB_EXPR\fR |
| 556 | The token describes one subexpression of an expression |
| 557 | (or an entire expression). |
| 558 | A subexpression may consist of a value |
| 559 | such as an integer literal, variable substitution, |
| 560 | or parenthesized subexpression; |
| 561 | it may also consist of an operator and its operands. |
| 562 | The token starts with the first non-blank character of the subexpression |
| 563 | up to but not including the space, brace, close-paren, or bracket |
| 564 | that terminates the subexpression. |
| 565 | This token is followed by one or more additional tokens |
| 566 | that describe the subexpression. |
| 567 | If the first sub-token after the \fBTCL_TOKEN_SUB_EXPR\fR token |
| 568 | is a \fBTCL_TOKEN_OPERATOR\fR token, |
| 569 | the subexpression consists of an operator and its token operands. |
| 570 | If the operator has no operands, the subexpression consists of |
| 571 | just the \fBTCL_TOKEN_OPERATOR\fR token. |
| 572 | Each operand is described by a \fBTCL_TOKEN_SUB_EXPR\fR token. |
| 573 | Otherwise, the subexpression is a value described by |
| 574 | one of the token types \fBTCL_TOKEN_WORD\fR, \fBTCL_TOKEN_TEXT\fR, |
| 575 | \fBTCL_TOKEN_BS\fR, \fBTCL_TOKEN_COMMAND\fR, |
| 576 | \fBTCL_TOKEN_VARIABLE\fR, and \fBTCL_TOKEN_SUB_EXPR\fR. |
| 577 | The \fInumComponents\fR field |
| 578 | counts the total number of sub-tokens that make up the subexpression; |
| 579 | this includes the sub-tokens for any nested \fBTCL_TOKEN_SUB_EXPR\fR tokens. |
| 580 | .TP |
| 581 | \fBTCL_TOKEN_OPERATOR\fR |
| 582 | The token describes one operator of an expression |
| 583 | such as \fB&&\fR or \fBhypot\fR. |
| 584 | An \fBTCL_TOKEN_OPERATOR\fR token is always preceded by a |
| 585 | \fBTCL_TOKEN_SUB_EXPR\fR token |
| 586 | that describes the operator and its operands; |
| 587 | the \fBTCL_TOKEN_SUB_EXPR\fR token's \fInumComponents\fR field |
| 588 | can be used to determine the number of operands. |
| 589 | A binary operator such as \fB*\fR |
| 590 | is followed by two \fBTCL_TOKEN_SUB_EXPR\fR tokens |
| 591 | that describe its operands. |
| 592 | A unary operator like \fB-\fR |
| 593 | is followed by a single \fBTCL_TOKEN_SUB_EXPR\fR token |
| 594 | for its operand. |
| 595 | If the operator is a math function such as \fBlog10\fR, |
| 596 | the \fBTCL_TOKEN_OPERATOR\fR token will give its name and |
| 597 | the following \fBTCL_TOKEN_SUB_EXPR\fR tokens will describe |
| 598 | its operands; |
| 599 | if there are no operands (as with \fBrand\fR), |
| 600 | no \fBTCL_TOKEN_SUB_EXPR\fR tokens follow. |
| 601 | There is one trinary operator, \fB?\fR, |
| 602 | that appears in if-then-else subexpressions |
| 603 | such as \fIx\fB?\fIy\fB:\fIz\fR; |
| 604 | in this case, the \fB?\fR \fBTCL_TOKEN_OPERATOR\fR token |
| 605 | is followed by three \fBTCL_TOKEN_SUB_EXPR\fR tokens for the operands |
| 606 | \fIx\fR, \fIy\fR, and \fIz\fR. |
| 607 | The \fInumComponents\fR field for a \fBTCL_TOKEN_OPERATOR\fR token |
| 608 | is always 0. |
| 609 | .PP |
| 610 | After \fBTcl_ParseCommand\fR returns, the first token pointed to by |
| 611 | the \fItokenPtr\fR field of the |
| 612 | Tcl_Parse structure always has type \fBTCL_TOKEN_WORD\fR or |
| 613 | \fBTCL_TOKEN_SIMPLE_WORD\fR. It is followed by the sub-tokens |
| 614 | that must be concatenated to produce the value of that word. |
| 615 | The next token is the \fBTCL_TOKEN_WORD\fR or \fBTCL_TOKEN_SIMPLE_WORD\fR |
| 616 | token for the second word, followed by sub-tokens for that |
| 617 | word, and so on until all \fInumWords\fR have been accounted |
| 618 | for. |
| 619 | .PP |
| 620 | After \fBTcl_ParseExpr\fR returns, the first token pointed to by |
| 621 | the \fItokenPtr\fR field of the |
| 622 | Tcl_Parse structure always has type \fBTCL_TOKEN_SUB_EXPR\fR. |
| 623 | It is followed by the sub-tokens that must be evaluated |
| 624 | to produce the value of the expression. |
| 625 | Only the token information in the Tcl_Parse structure |
| 626 | is modified: the \fIcommentStart\fR, \fIcommentSize\fR, |
| 627 | \fIcommandStart\fR, and \fIcommandSize\fR fields are not modified |
| 628 | by \fBTcl_ParseExpr\fR. |
| 629 | .PP |
| 630 | After \fBTcl_ParseBraces\fR returns, |
| 631 | the array of tokens pointed to by the \fItokenPtr\fR field of the |
| 632 | Tcl_Parse structure will contain a single \fBTCL_TOKEN_TEXT\fR token |
| 633 | if the braced string does not contain any backslash-newlines. |
| 634 | If the string does contain backslash-newlines, |
| 635 | the array of tokens will contain one or more |
| 636 | \fBTCL_TOKEN_TEXT\fR or \fBTCL_TOKEN_BS\fR sub-tokens |
| 637 | that must be concatenated to produce the value of the string. |
| 638 | If the braced string was just \fB{}\fR |
| 639 | (that is, the string was empty), |
| 640 | the single \fBTCL_TOKEN_TEXT\fR token will have a \fIsize\fR field |
| 641 | containing zero; |
| 642 | this ensures that at least one token appears |
| 643 | to describe the braced string. |
| 644 | Only the token information in the Tcl_Parse structure |
| 645 | is modified: the \fIcommentStart\fR, \fIcommentSize\fR, |
| 646 | \fIcommandStart\fR, and \fIcommandSize\fR fields are not modified |
| 647 | by \fBTcl_ParseBraces\fR. |
| 648 | .PP |
| 649 | After \fBTcl_ParseQuotedString\fR returns, |
| 650 | the array of tokens pointed to by the \fItokenPtr\fR field of the |
| 651 | Tcl_Parse structure depends on the contents of the quoted string. |
| 652 | It will consist of one or more \fBTCL_TOKEN_TEXT\fR, \fBTCL_TOKEN_BS\fR, |
| 653 | \fBTCL_TOKEN_COMMAND\fR, and \fBTCL_TOKEN_VARIABLE\fR sub-tokens. |
| 654 | The array always contains at least one token; |
| 655 | for example, if the argument \fIstring\fR is empty, |
| 656 | the array returned consists of a single \fBTCL_TOKEN_TEXT\fR token |
| 657 | with a zero \fIsize\fR field. |
| 658 | Only the token information in the Tcl_Parse structure |
| 659 | is modified: the \fIcommentStart\fR, \fIcommentSize\fR, |
| 660 | \fIcommandStart\fR, and \fIcommandSize\fR fields are not modified. |
| 661 | .PP |
| 662 | After \fBTcl_ParseVarName\fR returns, the first token pointed to by |
| 663 | the \fItokenPtr\fR field of the |
| 664 | Tcl_Parse structure always has type \fBTCL_TOKEN_VARIABLE\fR. It |
| 665 | is followed by the sub-tokens that make up the variable name as |
| 666 | described above. The total length of the variable name is |
| 667 | contained in the \fIsize\fR field of the first token. |
| 668 | As in \fBTcl_ParseExpr\fR, |
| 669 | only the token information in the Tcl_Parse structure |
| 670 | is modified by \fBTcl_ParseVarName\fR: |
| 671 | the \fIcommentStart\fR, \fIcommentSize\fR, |
| 672 | \fIcommandStart\fR, and \fIcommandSize\fR fields are not modified. |
| 673 | .PP |
| 674 | All of the character pointers in the |
| 675 | Tcl_Parse and Tcl_Token structures refer |
| 676 | to characters in the \fIstring\fR argument passed to |
| 677 | \fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, |
| 678 | \fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR. |
| 679 | .PP |
| 680 | There are additional fields in the Tcl_Parse structure after the |
| 681 | \fInumTokens\fR field, but these are for the private use of |
| 682 | \fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, |
| 683 | \fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR; they should not be |
| 684 | referenced by code outside of these procedures. |
| 685 | |
| 686 | .SH KEYWORDS |
| 687 | backslash substitution, braces, command, expression, parse, token, variable substitution |