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diff --git a/doc/gawktexi.in b/doc/gawktexi.in index 37ecbc9f..81a24079 100644 --- a/doc/gawktexi.in +++ b/doc/gawktexi.in @@ -803,6 +803,8 @@ particular records in a file and perform operations upon them. once. * Shell Quoting:: A function to quote strings for the shell. +* Isnumeric Function:: A function to test whether a value + is numeric. * Data File Management:: Functions for managing command-line data files. * Filetrans Function:: A function for handling data file @@ -21374,6 +21376,7 @@ programming use. * Getlocaltime Function:: A function to get formatted times. * Readfile Function:: A function to read an entire file at once. * Shell Quoting:: A function to quote strings for the shell. +* Isnumeric Function:: A function to test whether a value is numeric. @end menu @node Strtonum Function @@ -22164,6 +22167,35 @@ function shell_quote(s, # parameter @c endfile @end example +@node Isnumeric Function +@subsection Checking whether a value is numeric + +A frequent programming question is how to ascertain whether a value is numeric. +This can be solved by using this example function @code{isnumeric()}, which +employs the trick of converting a string value to user input by using the +@code{split()} function: + +@cindex @code{isnumeric()} user-defined function +@cindex user-defined @subentry function @subentry @code{isnumeric()} +@example +@c file eg/lib/isnumeric.awk +# isnumeric --- check whether a value is numeric + +function isnumeric(x, f) +@{ + switch (typeof(x)) @{ + case "strnum": + case "number": + return 1 + case "string": + return (split(x, f, " ") == 1) && (typeof(f[1]) == "strnum") + default: + return 0 + @} +@} +@c endfile +@end example + @node Data File Management @section @value{DDF} Management |