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M4(local) UNIX Programmer's Manual M4(local) NAME pd m4 - macro processor ORIGIN MetaSystems SYNOPSIS m4[ options ] DESCRIPTION Pd M4 is a un*x M4 look-alike macro processor intended as a front end for Ratfor, Pascal, and other languages that do not have a built-in macro processing capability. Pd M4 reads standard input, the processed text is written on the standard output. The options and their effects are as follows: -Dname[=val] Defines name to val or to null in val's absence. -Uname undefines name. Macro calls have the form: name(arg1,arg2, ..., argn) The ( must immediately follow the name of the macro. If the name of a defined macro is not followed by a (, it is taken to be a call of that macro with no arguments, i.e. name(). Potential macro names consist of alphabetic letters and digits. Leading unquoted blanks, tabs and newlines are ignored while collecting arguments. Left and right single quotes are used to quote strings. The value of a quoted string is the string stripped of the quotes. When a macro name is recognized, its arguments are collected by searching for a matching ). If fewer arguments are sup- plied than are in the macro definition, the trailing argu- ments are taken to be null. Macro evaluation proceeds nor- mally during the collection of the arguments, and any commas or right parentheses which happen to turn up within the value of a nested call are as effective as those in the ori- ginal input text. (This is typically referred as inside-out macro expansion.) After argument collection, the value of the macro is pushed back onto the input stream and res- canned. Printed 5/16/88 30 Aug 1987 1 M4(local) UNIX Programmer's Manual M4(local) Pd M4 makes available the following built-in macros. They may be redefined, but once this is done the original meaning is lost. Their values are null unless otherwise stated. define usage: define(name [, val]) the second argument is installed as the value of the macro whose name is the first argument. If there is no second argument, the value is null. Each occurrence of $n in the replace- ment text, where n is a digit, is replaced by the n-th argument. Argument 0 is the name of the macro; missing arguments are replaced by the null string. defn usage: defn(name [, name ...]) returns the quoted definition of its argument(s). Useful in renaming macros. undefine usage: undefine(name [, name ...]) removes the definition of the macro(s) named. If there is more than one definition for the named macro, (due to previous use of pushdef) all definitions are removed. pushdef usage: pushdef(name [, val]) like define, but saves any previous definition by stacking the current definition. popdef usage: popdef(name [, name ...]) removes current definition of its argument(s), exposing the previous one if any. ifdef usage: ifdef(name, if-def [, ifnot-def]) if the first argument is defined, the value is the second argument, otherwise the third. If there is no third argument, the value is null. A word indicating the current operating system is predefined. (e.g. unix or vms) shift usage: shift(arg, arg, arg, ...) returns all but its first argument. The other arguments are quoted and pushed back with com- mas in between. The quoting nullifies the effect of the extra scan that will subse- quently be performed. changequote usage: changequote(lqchar, rqchar) change quote symbols to the first and second arguments. With no arguments, the quotes are reset back to the default characters. (i.e., ). Printed 5/16/88 30 Aug 1987 2 M4(local) UNIX Programmer's Manual M4(local) changecom usage: changecom(lcchar, rcchar) change left and right comment markers from the default # and newline. With no arguments, the comment mechanism is reset back to the default characters. With one argument, the left marker becomes the argument and the right marker becomes newline. With two arguments, both markers are affected. divert usage: divert(divnum) m4 maintains 10 output streams, numbered 0-9. initially stream 0 is the current stream. The divert macro changes the current output stream to its (digit-string) argument. Output diverted to a stream other than 0 through 9 disappears into bitbucket. undivert usage: undivert([divnum [, divnum ...]]) causes immediate output of text from diver- sions named as argument(s), or all diversions if no argument. Text may be undiverted into another diversion. Undiverting discards the diverted text. At the end of input processing, M4 forces an automatic undivert, unless m4wrap is defined. divnum usage: divnum() returns the value of the current output stream. dnl usage: dnl() reads and discards characters up to and including the next newline. ifelse usage: ifelse(arg, arg, if-same [, ifnot-same | arg, arg ...]) has three or more arguments. If the first argument is the same string as the second, then the value is the third argument. If not, and if there are more than four arguments, the process is repeated with arguments 4, 5, 6 and 7. Otherwise, the value is either the fourth string, or, if it is not present, null. incr usage: incr(num) returns the value of its argument incremented by 1. The value of the argument is calculated by interpreting an initial digit-string as a decimal number. decr usage: decr(num) returns the value of its argument decremented Printed 5/16/88 30 Aug 1987 3 M4(local) UNIX Programmer's Manual M4(local) by 1. eval usage: eval(expression) evaluates its argument as a constant expres- sion, using integer arithmetic. The evalua- tion mechanism is very similar to that of cpp (#if expression). The expression can involve only integer constants and character con- stants, possibly connected by the binary operators * / % + - >> << < > <= >= == != & ^ | && || or the unary operators - ~ ! or by the ter- nary operator ? : . Parentheses may be used for grouping. Octal numbers may be specified as in C. len usage: len(string) returns the number of characters in its argu- ment. index usage: index(search-string, string) returns the position in its first argument where the second argument begins (zero ori- gin), or -1 if the second argument does not occur. substr usage: substr(string, index [, length]) returns a substring of its first argument. The second argument is a zero origin number selecting the first character (internally treated as an expression); the third argument indicates the length of the substring. A missing third argument is taken to be large enough to extend to the end of the first string. translit usage: translit(source, from [, to]) transliterates the characters in its first argument from the set given by the second argument to the set given by the third. If the third argument is shorter than the second, all extra characters in the second argument are deleted from the first argument. If the third argument is missing altogether, all characters in the second argument are deleted from the first argument. include usage: include(filename) returns the contents of the file named in the Printed 5/16/88 30 Aug 1987 4 M4(local) UNIX Programmer's Manual M4(local) argument. sinclude usage: sinclude(filename) is identical to include, except that it says nothing if the file is inaccessible. paste usage: paste(filename) returns the contents of the file named in the argument without any processing, unlike include. spaste usage: spaste(filename) is identical to paste, except that it says nothing if the file is inaccessible. syscmd usage: syscmd(command) executes the UNIX command given in the first argument. No value is returned. sysval usage: sysval() is the return code from the last call to syscmd. maketemp usage: maketemp(string) fills in a string of XXXXXX in its argument with the current process ID. m4exit usage: m4exit([exitcode]) causes immediate exit from m4. Argument 1, if given, is the exit code; the default is 0. m4wrap usage: m4wrap(m4-macro-or-built-in) argument 1 will be pushed back at final EOF; example: m4wrap(`dumptable()'). errprint usage: errprint(str [, str, str, ...]) prints its argument(s) on stderr. If there is more than one argument, each argument is separated by a space during the output. dumpdef usage: dumpdef([name, name, ...]) prints current names and definitions, for the named items, or for all if no arguments are given. AUTHOR Ozan S. Yigit (oz) BUGS Pd M4 is distributed at the source level, and does not require an expensive license agreement. Printed 5/16/88 30 Aug 1987 5 M4(local) UNIX Programmer's Manual M4(local) A sufficiently complex M4 macro set is about as readable as APL. All complex uses of M4 require the ability to program in deep recursion. Previous lisp experience is recommended. Pd M4 is slower than V7 M4. EXAMPLES The following macro program illustrates the type of things that can be done with M4. changequote(<,>) define(HASHVAL,99) dnl define(hash,<expr(str(substr($1,1),0)%HASHVAL)>) dnl define(str, <ifelse($1,",$2, <str(substr(<$1>,1),<expr($2+'substr($1,0,1)')>)>) >) dnl define(KEYWORD,<$1,hash($1),>) dnl define(TSTART, <struct prehash { char *keyword; int hashval; } keytab[] = {>) dnl define(TEND,< "",0 };>) dnl Thus a keyword table containing the keyword string and its pre-calculated hash value may be generated thus: TSTART KEYWORD("foo") KEYWORD("bar") KEYWORD("baz") TEND which will expand into: struct prehash { char *keyword; int hashval; } keytab[] = { "foo",27, "bar",12, "baz",20, "",0 }; Presumably, such a table would speed up the installation of the keywords into a dynamic hash table. (Note that the above macro cannot be used with M4, since eval does not handle character constants.) Printed 5/16/88 30 Aug 1987 6 M4(local) UNIX Programmer's Manual M4(local) SEE ALSO cc(1), m4(1), cpp(1). The M4 Macro Processor by B. W. Ker- nighan and D. M. Ritchie. Printed 5/16/88 30 Aug 1987 7