'\" '\" Generated from file 'critcl_cproc\&.man' by tcllib/doctools with format 'nroff' '\" Copyright (c) Jean-Claude Wippler '\" Copyright (c) Steve Landers '\" Copyright (c) 2011-2015 Andreas Kupries '\" .TH "critcl-cproc-types" 3tcl 3\&.1\&.17 doc "C Runtime In Tcl (CriTcl)" .\" The -*- nroff -*- definitions below are for supplemental macros used .\" in Tcl/Tk manual entries. .\" .\" .AP type name in/out ?indent? .\" Start paragraph describing an argument to a library procedure. .\" type is type of argument (int, etc.), in/out is either "in", "out", .\" or "in/out" to describe whether procedure reads or modifies arg, .\" and indent is equivalent to second arg of .IP (shouldn't ever be .\" needed; use .AS below instead) .\" .\" .AS ?type? ?name? .\" Give maximum sizes of arguments for setting tab stops. Type and .\" name are examples of largest possible arguments that will be passed .\" to .AP later. If args are omitted, default tab stops are used. .\" .\" .BS .\" Start box enclosure. From here until next .BE, everything will be .\" enclosed in one large box. .\" .\" .BE .\" End of box enclosure. .\" .\" .CS .\" Begin code excerpt. .\" .\" .CE .\" End code excerpt. .\" .\" .VS ?version? ?br? .\" Begin vertical sidebar, for use in marking newly-changed parts .\" of man pages. The first argument is ignored and used for recording .\" the version when the .VS was added, so that the sidebars can be .\" found and removed when they reach a certain age. If another argument .\" is present, then a line break is forced before starting the sidebar. .\" .\" .VE .\" End of vertical sidebar. .\" .\" .DS .\" Begin an indented unfilled display. .\" .\" .DE .\" End of indented unfilled display. .\" .\" .SO ?manpage? .\" Start of list of standard options for a Tk widget. The manpage .\" argument defines where to look up the standard options; if .\" omitted, defaults to "options". The options follow on successive .\" lines, in three columns separated by tabs. .\" .\" .SE .\" End of list of standard options for a Tk widget. .\" .\" .OP cmdName dbName dbClass .\" Start of description of a specific option. cmdName gives the .\" option's name as specified in the class command, dbName gives .\" the option's name in the option database, and dbClass gives .\" the option's class in the option database. .\" .\" .UL arg1 arg2 .\" Print arg1 underlined, then print arg2 normally. .\" .\" .QW arg1 ?arg2? .\" Print arg1 in quotes, then arg2 normally (for trailing punctuation). .\" .\" .PQ arg1 ?arg2? .\" Print an open parenthesis, arg1 in quotes, then arg2 normally .\" (for trailing punctuation) and then a closing parenthesis. .\" .\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. .if t .wh -1.3i ^B .nr ^l \n(.l .ad b .\" # Start an argument description .de AP .ie !"\\$4"" .TP \\$4 .el \{\ . ie !"\\$2"" .TP \\n()Cu . el .TP 15 .\} .ta \\n()Au \\n()Bu .ie !"\\$3"" \{\ \&\\$1 \\fI\\$2\\fP (\\$3) .\".b .\} .el \{\ .br .ie !"\\$2"" \{\ \&\\$1 \\fI\\$2\\fP .\} .el \{\ \&\\fI\\$1\\fP .\} .\} .. .\" # define tabbing values for .AP .de AS .nr )A 10n .if !"\\$1"" .nr )A \\w'\\$1'u+3n .nr )B \\n()Au+15n .\" .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n .nr )C \\n()Bu+\\w'(in/out)'u+2n .. .AS Tcl_Interp Tcl_CreateInterp in/out .\" # BS - start boxed text .\" # ^y = starting y location .\" # ^b = 1 .de BS .br .mk ^y .nr ^b 1u .if n .nf .if n .ti 0 .if n \l'\\n(.lu\(ul' .if n .fi .. .\" # BE - end boxed text (draw box now) .de BE .nf .ti 0 .mk ^t .ie n \l'\\n(^lu\(ul' .el \{\ .\" Draw four-sided box normally, but don't draw top of .\" box if the box started on an earlier page. .ie !\\n(^b-1 \{\ \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .el \}\ \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .\} .fi .br .nr ^b 0 .. .\" # VS - start vertical sidebar .\" # ^Y = starting y location .\" # ^v = 1 (for troff; for nroff this doesn't matter) .de VS .if !"\\$2"" .br .mk ^Y .ie n 'mc \s12\(br\s0 .el .nr ^v 1u .. .\" # VE - end of vertical sidebar .de VE .ie n 'mc .el \{\ .ev 2 .nf .ti 0 .mk ^t \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' .sp -1 .fi .ev .\} .nr ^v 0 .. .\" # Special macro to handle page bottom: finish off current .\" # box/sidebar if in box/sidebar mode, then invoked standard .\" # page bottom macro. .de ^B .ev 2 'ti 0 'nf .mk ^t .if \\n(^b \{\ .\" Draw three-sided box if this is the box's first page, .\" draw two sides but no top otherwise. .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .\} .if \\n(^v \{\ .nr ^x \\n(^tu+1v-\\n(^Yu \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c .\} .bp 'fi .ev .if \\n(^b \{\ .mk ^y .nr ^b 2 .\} .if \\n(^v \{\ .mk ^Y .\} .. .\" # DS - begin display .de DS .RS .nf .sp .. .\" # DE - end display .de DE .fi .RE .sp .. .\" # SO - start of list of standard options .de SO 'ie '\\$1'' .ds So \\fBoptions\\fR 'el .ds So \\fB\\$1\\fR .SH "STANDARD OPTIONS" .LP .nf .ta 5.5c 11c .ft B .. .\" # SE - end of list of standard options .de SE .fi .ft R .LP See the \\*(So manual entry for details on the standard options. .. .\" # OP - start of full description for a single option .de OP .LP .nf .ta 4c Command-Line Name: \\fB\\$1\\fR Database Name: \\fB\\$2\\fR Database Class: \\fB\\$3\\fR .fi .IP .. .\" # CS - begin code excerpt .de CS .RS .nf .ta .25i .5i .75i 1i .. .\" # CE - end code excerpt .de CE .fi .RE .. .\" # UL - underline word .de UL \\$1\l'|0\(ul'\\$2 .. .\" # QW - apply quotation marks to word .de QW .ie '\\*(lq'"' ``\\$1''\\$2 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\$2 .. .\" # PQ - apply parens and quotation marks to word .de PQ .ie '\\*(lq'"' (``\\$1''\\$2)\\$3 .\"" fix emacs highlighting .el (\\*(lq\\$1\\*(rq\\$2)\\$3 .. .\" # QR - quoted range .de QR .ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3 .. .\" # MT - "empty" string .de MT .QW "" .. .BS .SH NAME critcl-cproc-types \- Critcl - cproc Type Reference .SH SYNOPSIS package require \fBTcl 8\&.4\fR .sp package require \fBcritcl ?3\&.1\&.17?\fR .sp \fB::critcl::has-resulttype\fR \fIname\fR .sp \fB::critcl::resulttype\fR \fIname\fR \fIbody\fR ?\fIctype\fR? .sp \fB::critcl::resulttype\fR \fIname\fR \fB=\fR \fIorigname\fR .sp \fB::critcl::has-argtype\fR \fIname\fR .sp \fB::critcl::argtype\fR \fIname\fR \fIbody\fR ?\fIctype\fR? ?\fIctypefun\fR? .sp \fB::critcl::argtype\fR \fIname\fR \fB=\fR \fIorigname\fR .sp \fB::critcl::argtypesupport\fR \fIname\fR \fIcode\fR ?\fIguard\fR? .sp \fB::critcl::argtyperelease\fR \fIname\fR \fIcode\fR .sp .BE .SH DESCRIPTION .PP Welcome to the \fIC Runtime In Tcl\fR, \fICriTcl\fR for short, a system to build C extension packages for Tcl on the fly, from C code embedded within Tcl scripts, for all who wish to make their code go faster\&. .PP This document is a breakout of the descriptions for the predefined argument- and result-types usable with the \fBcritcl::cproc\fR command, as detailed in the reference manpage for the \fBcritcl\fR package, plus the information on how to extend the predefined set with custom types\&. The breakout was made to make this information easier to find (toplevel document vs\&. having to search the large main reference)\&. .PP Its intended audience are developers wishing to write Tcl packages with embedded C code\&. .SH "STANDARD ARGUMENT TYPES" .TP Tcl_Obj* .TP object The function takes an argument of type \fBTcl_Obj*\fR\&. No argument checking is done\&. The Tcl level word is passed to the argument as-is\&. .TP pstring The function takes an argument of type \fBcritcl_pstring\fR containing the original \fBTcl_Obj*\fR reference of the Tcl argument, plus the length of the string and a pointer to the character array\&. .CS typedef struct critcl_pstring { Tcl_Obj* o; char* s; int len; } critcl_pstring; .CE .TP list The function takes an argument of type \fBcritcl_list\fR containing the original \fBTcl_Obj*\fR reference of the Tcl argument, plus the length of the Tcl list and a pointer to the array of the list elements\&. .CS typedef struct critcl_list { Tcl_Obj* o; Tcl_Obj** v; int c; } critcl_list; .CE .IP The Tcl argument must be convertible to \fBList\fR, an error is thrown otherwise\&. .TP bytearray .TP rawchar* .TP rawchar The function takes an argument of type \fBchar*\fR\&. The Tcl argument must be convertible to \fBByteArray\fR, an error is thrown otherwise\&. \fINote\fR that the length of the \fBByteArray\fR is \fInot\fR passed to the function, making this type not very usable\&. .TP bytes This is the \fInew\fR and usable \fBByteArray\fR type\&. .sp The function takes an argument of type \fBcritcl_bytes\fR containing the original \fBTcl_Obj*\fR reference of the Tcl argument, plus the length of the byte array and a pointer to the byte data\&. .CS typedef struct critcl_bytes { Tcl_Obj* o; char* s; int len; } critcl_list; .CE .IP The Tcl argument must be convertible to \fBByteArray\fR, an error is thrown otherwise\&. .TP char* The function takes an argument of type \fBchar*\fR\&. The string representation of the Tcl argument is passed in\&. .TP double The function takes an argument of type \fBdouble\fR\&. The Tcl argument must be convertible to \fBDouble\fR, an error is thrown otherwise\&. .TP float The function takes an argument of type \fBfloat\fR\&. The Tcl argument must be convertible to \fBDouble\fR, an error is thrown otherwise\&. .TP boolean .TP bool The function takes an argument of type \fBint\fR\&. The Tcl argument must be convertible to \fBBoolean\fR, an error is thrown otherwise\&. .TP int The function takes an argument of type \fBint\fR\&. The Tcl argument must be convertible to \fBInt\fR, an error is thrown otherwise\&. .TP long The function takes an argument of type \fBlong int\fR\&. The Tcl argument must be convertible to \fBLong\fR, an error is thrown otherwise\&. .TP wideint The function takes an argument of type \fBTcl_WideInt\fR\&. The Tcl argument must be convertible to \fBWideInt\fR, an error is thrown otherwise\&. .TP void* .TP double* .TP float* .TP int* The function takes an argument of the same-named C type\&. The Tcl argument must be convertible to ByteArray, an error is thrown otherwise\&. The bytes in the ByteArray are then re-interpreted as the raw representation of a single C pointer of the given type which is then passed as argument to the function\&. In other words, this is for Tcl values somehow holding raw C pointers, i\&.e\&. memory addresses\&. .sp \fIAttention\fR: These types are considered \fIDEPRECATED\fR\&. It is planned to remove their documentation in release 3\&.2, and their implementation in release 3\&.3\&. Their deprecation can be undone if good use cases are shown\&. .PP .SH "STANDARD RESULT TYPES" .TP Tcl_Obj* .TP object The function returns a value of type \fBTcl_Obj*\fR\&. This value becomes the interpreter result, if not \fB0\fR\&. The Tcl status is \fBTCL_ERROR\fR when a \fB0\fR is returned, and \fBTCL_OK\fR otherwise\&. .sp \fINote\fR how it is the responsibility of the function to set the interpreter result to an appropriate error message when returning \fB0\fR\&. .sp \fIAttention\fR: The conversion assumes that the value belonged to the function, with an associated reference count, and decrements the reference count to indicate the loss of ownership by the function\&. This means that it is an error to return a value whose reference count is zero\&. The system will crash at some point after the return due to reuse of the freed memory\&. .TP Tcl_Obj*0 .TP object0 The function returns a value of type \fBTcl_Obj*\fR\&. This value becomes the interpreter result, if not \fB0\fR\&. The Tcl status is \fBTCL_ERROR\fR when a \fB0\fR is returned, and \fBTCL_OK\fR otherwise\&. .sp \fINote\fR how it is the responsibility of the function to set the interpreter result to an appropriate error message when returning \fB0\fR\&. .sp \fIAttention\fR: Contrary to \fBTcl_Obj*\fR above this conversion assumes that the returned value has a reference count of \fB0\fR and performs \fIno\fR decrement\&. Returning a value whose reference count is greater than zero will likely cause a memory leak\&. .TP char* .TP vstring The function returns a value of type \fBchar*\fR\&. This value becomes the interpreter result, wrapped in a \fBString\fR\&. It is assumed that the string is volatile in some way, with the wrapping in a \fBString\fR duplicating it before making it the result, ensuring that we will not access a dangling pointer in the future\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP const char* Like type \fBchar*\fR above, except that the returned string is \fBconst\fR-qualified\&. .TP string .TP dstring The function returns a value of type \fBchar*\fR\&. Contrary to the previous string types here it is assumed that the value is dynamically allocated, via \fBTcl_Alloc\fR\&. This value becomes the interpreter result, as usual, but is \fInot\fR copied\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP double The function returns a value of type \fBdouble\fR\&. This value becomes the interpreter result, properly wrapped as a \fBDouble\fR\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP float The function returns a value of type \fBfloat\fR\&. This value becomes the interpreter result, properly wrapped as a \fBDouble\fR\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP boolean .TP bool The function returns a value of type \fBint\fR, interpreted as boolean\&. This value becomes the interpreter result, properly wrapped as a \fBInt\fR\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP int The function returns a value of type \fBint\fR\&. This value becomes the interpreter result, properly wrapped as a \fBInt\fR\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP long The function returns a value of type \fBlong int\fR\&. This value becomes the interpreter result, properly wrapped as a \fBLong\fR\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP wideint The function returns a value of type \fBTcl_WideInt\fR\&. This value becomes the interpreter result, properly wrapped as a \fBWideInt\fR\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .TP ok The function returns a value of type \fBint\fR\&. It is interpreted as the Tcl status code\&. The interpreter result is left untouched (empty)\&. For a different outcome the function has to set the interpreter result by itself\&. .TP void The function does not return a value\&. The interpreter result is left untouched (empty)\&. For a different outcome the function has to set the interpreter result by itself\&. The Tcl status is \fIalways\fR \fBTCL_OK\fR\&. .PP .SH "ADVANCED: ADDING TYPES" While the \fBcritcl::cproc\fR command understands the most common C types (as per the previous 2 sections), sometimes this is not enough\&. .PP To get around this limitation the commands in this section enable users of \fBcritcl\fR to extend the set of argument and result types understood by \fBcritcl::cproc\fR\&. In other words, they allow them to define their own, custom, types\&. .TP \fB::critcl::has-resulttype\fR \fIname\fR This command tests if the named result-type is known or not\&. It returns a boolean value, \fBtrue\fR if the type is known and \fBfalse\fR otherwise\&. .TP \fB::critcl::resulttype\fR \fIname\fR \fIbody\fR ?\fIctype\fR? This command defines the result type \fIname\fR, and associates it with the C code doing the conversion (\fIbody\fR) from C to Tcl\&. The C return type of the associated function, also the C type of the result variable, is \fIctype\fR\&. This type defaults to \fIname\fR if it is not specified\&. .sp If \fIname\fR is declared already an error will be thrown\&. \fIAttention!\fR The standard result type \fBvoid\fR is special as it has no accompanying result variable\&. This cannot be expressed by this extension command\&. .sp The \fIbody\fR's responsibility is the conversion of the functions result into a Tcl result and a Tcl status\&. The first has to be set into the interpreter we are in, and the second has to be returned\&. .sp The C code of \fIbody\fR is guaranteed to be called last in the wrapper around the actual implementation of the \fBcproc\fR in question and has access to the following environment: .RS .TP \fBinterp\fR A Tcl_Interp* typed C variable referencing the interpreter the result has to be stored into\&. .TP \fBrv\fR The C variable holding the result to convert, of type \fIctype\fR\&. .RE .IP As examples here are the definitions of two standard result types: .CS resulttype int { Tcl_SetObjResult(interp, Tcl_NewIntObj(rv)); return TCL_OK; } resulttype ok { /* interp result must be set by cproc body */ return rv; } int .CE .TP \fB::critcl::resulttype\fR \fIname\fR \fB=\fR \fIorigname\fR This form of the \fBresulttype\fR command declares \fIname\fR as an alias of result type \fIorigname\fR, which has to be defined already\&. If this is not the case an error is thrown\&. .TP \fB::critcl::has-argtype\fR \fIname\fR This command tests if the named argument-type is known or not\&. It returns a boolean value, \fBtrue\fR if the type is known and \fBfalse\fR otherwise\&. .TP \fB::critcl::argtype\fR \fIname\fR \fIbody\fR ?\fIctype\fR? ?\fIctypefun\fR? This command defines the argument type \fIname\fR, and associates it with the C code doing the conversion (\fIbody\fR) from Tcl to C The C type of the variable to hold the conversion result is \fIctype\fR and the type of the function argument itself is \fIctypefun\fR\&. Both types default to \fIname\fR if they are not specified (or the empty string)\&. .sp If \fIname\fR is declared already an error will be thrown\&. .sp The \fIbody\fR's responsibility is the conversion of a command's Tcl_Obj* argument into a C value for the underlying function and its storage in a helper variable\&. .sp The C code of \fIbody\fR is guaranteed to be called inside of a separate C code block (thus allowing the use of local variables) which has access to the following environment: .RS .TP \fBinterp\fR A Tcl_Interp* typed C variable referencing the interpreter the code is running in\&. .TP \fB@@\fR A placeholder for the Tcl_Obj*-valued C expression providing the value of the argument to convert\&. .TP \fB@A\fR A placeholder for the name of the C variable to store the converted argument into\&. .RE .IP As examples here are the definitions of two standard argument types: .CS argtype int { if (Tcl_GetIntFromObj(interp, @@, &@A) != TCL_OK) return TCL_ERROR; } argtype float { double t; if (Tcl_GetDoubleFromObj(interp, @@, &t) != TCL_OK) return TCL_ERROR; @A = (float) t; } .CE .TP \fB::critcl::argtype\fR \fIname\fR \fB=\fR \fIorigname\fR This form of the \fBargtype\fR command declares \fIname\fR as an alias of argument type \fIorigname\fR, which has to be defined already\&. If this is not the case an error is thrown\&. .TP \fB::critcl::argtypesupport\fR \fIname\fR \fIcode\fR ?\fIguard\fR? This command defines a C code fragment for the already defined argument type \fIname\fR which will be inserted before all functions using that type\&. Its purpose is the definition of any supporting C types needed by the argument type\&. If the type is used by many functions the system ensures that only the first of the multiple insertions of the code fragment is active, and the others disabled\&. The guard identifier is normally derived from \fIname\fR, but can also be set explicitly, via \fIguard\fR\&. This latter allows different custom types to share a common support structure without having to perform their own guarding\&. .TP \fB::critcl::argtyperelease\fR \fIname\fR \fIcode\fR This command defines a C code fragment for the already defined argument type \fIname\fR which will be inserted whenever the worker function of a \fBcritcl::cproc\fR returns to the shim\&. It is the responsibility of this fragment to unconditionally release any resources the \fBcritcl::argtype\fR conversion code allocated\&. An example of this are the \fIvariadic\fR types for the support of the special, variadic \fIargs\fR argument to \fBcritcl::cproc\fR's\&. They allocate a C array for the collected arguments which has to be released when the worker returns\&. This command defines the C code for doing that\&. .PP .SH EXAMPLES The examples shown here have been drawn from section "Embedding C" in the document about \fIUsing CriTcl\fR\&. Please see that document for many more examples\&. .SS "A SIMPLE PROCEDURE" Starting simple, let us assume that the Tcl code in question is something like .CS proc math {x y z} { return [expr {(sin($x)*rand())/$y**log($z)}] } .CE with the expression pretending to be something very complex and slow\&. Converting this to C we get: .CS critcl::cproc math {double x double y double z} double { double up = rand () * sin (x); double down = pow(y, log (z)); return up/down; } .CE Notable about this translation: .IP [1] All the arguments got type information added to them, here "double"\&. Like in C the type precedes the argument name\&. Other than that it is pretty much a Tcl dictionary, with keys and values swapped\&. .IP [2] We now also have to declare the type of the result, here "double", again\&. .IP [3] The reference manpage lists all the legal C types supported as arguments and results\&. .PP .SS "CUSTOM TYPES, INTRODUCTION" When writing bindings to external libraries \fBcritcl::cproc\fR is usually the most convenient way of writing the lower layers\&. This is however hampered by the fact that critcl on its own only supports a few standard (arguably the most import) standard types, whereas the functions we wish to bind most certainly will use much more, specific to the library's function\&. .PP The critcl commands \fBargtype\fR, \fBresulttype\fR and their adjuncts are provided to help here, by allowing a developer to extend critcl's type system with custom conversions\&. .PP This and the three following sections will demonstrate this, from trivial to complex\&. .PP The most trivial use is to create types which are aliases of existing types, standard or other\&. As an alias it simply copies and uses the conversion code from the referenced types\&. .PP Our example is pulled from an incomplete project of mine, a binding to \fIJeffrey Kegler\fR's \fIlibmarpa\fR library managing Earley parsers\&. Several custom types simply reflect the typedef's done by the library, to make the \fBcritcl::cproc\fRs as self-documenting as the underlying library functions themselves\&. .CS critcl::argtype Marpa_Symbol_ID = int critcl::argtype Marpa_Rule_ID = int critcl::argtype Marpa_Rule_Int = int critcl::argtype Marpa_Rank = int critcl::argtype Marpa_Earleme = int critcl::argtype Marpa_Earley_Set_ID = int \&.\&.\&. method sym-rank: proc { Marpa_Symbol_ID sym Marpa_Rank rank } Marpa_Rank { return marpa_g_symbol_rank_set (instance->grammar, sym, rank); } \&.\&.\&. .CE .SS "CUSTOM TYPES, SEMI-TRIVIAL" A more involved custom argument type would be to map from Tcl strings to some internal representation, like an integer code\&. .PP The first example is taken from the \fBtclyaml\fR package, a binding to the \fBlibyaml\fR library\&. In a few places we have to map readable names for block styles, scalar styles, etc\&. to the internal enumeration\&. .CS critcl::argtype yaml_sequence_style_t { if (!encode_sequence_style (interp, @@, &@A)) return TCL_ERROR; } \&.\&.\&. critcl::ccode { static const char* ty_block_style_names [] = { "any", "block", "flow", NULL }; static int encode_sequence_style (Tcl_Interp* interp, Tcl_Obj* style, yaml_sequence_style_t* estyle) { int value; if (Tcl_GetIndexFromObj (interp, style, ty_block_style_names, "sequence style", 0, &value) != TCL_OK) { return 0; } *estyle = value; return 1; } } \&.\&.\&. method sequence_start proc { pstring anchor pstring tag int implicit yaml_sequence_style_t style } ok { /* Syntax: seq_start