[PATCH] New functions to strip whitespace from strings

[John Darrington]

        * src/std.pk (ltrim): New function.
        * src/std.pk (rtrim): New function.
        * doc/poke.texi (String Functions): New chapter.
        * testsuite/poke.std/ltrim.pk: New file.
        * testsuite/poke.std/rtrim.pk: New file.
---
 ChangeLog                   |  8 ++++++++
 doc/poke.texi               | 37 +++++++++++++++++++++++++++++++++++++
 src/std.pk                  | 27 +++++++++++++++++++++++++++
 testsuite/poke.std/ltrim.pk |  4 ++++
 testsuite/poke.std/rtrim.pk |  4 ++++
 5 files changed, 80 insertions(+)
 create mode 100644 testsuite/poke.std/ltrim.pk
 create mode 100644 testsuite/poke.std/rtrim.pk

diff --git a/ChangeLog b/ChangeLog
index f2a5d66..5acd43c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2019-11-12 John Darrington <address@hidden>
 
+       * src/std.pk (ltrim): New function.
+       * src/std.pk (rtrim): New function.
+       * doc/poke.texi (String Functions): New chapter.
+       * testsuite/poke.std/ltrim.pk: New file.
+       * testsuite/poke.std/rtrim.pk: New file.
+
+2019-11-12 John Darrington <address@hidden>
+
         * src/pk-file.c (pk_cmd_file): Use strerror for reason.
         (pk_cmd_load_file): ditto.
 
diff --git a/doc/poke.texi b/doc/poke.texi
index 0b0a015..c1620be 100644
--- a/doc/poke.texi
+++ b/doc/poke.texi
@@ -103,6 +103,7 @@ The Standard Library
 * Standard Integral Types::    int, long and the like.
 * Standard Offset Types::      off64 and the like.
 * Conversion Functions::       catos, atoi, etc.
+* String Functions::           Functions which deal with strings.
 * Sorting Functions::          qsort.
 
 Hacking poke
@@ -1440,6 +1441,9 @@ Poke supports a notion of @dfn{strings} which is very 
similar to the C
 programming language: a string value is a sequence of characters that
 is terminated by the so-called @dfn{null character}.
 
+The standard library provides functions which process strings.
+@xref{String Functions}.
+
 @menu
 * String Literals::            Writing string values.
 * String Types::               string.
@@ -3511,6 +3515,39 @@ after the parsed integer.  Thus, this works:
 10L
 @end example
 
+@node String Functions
+@chapter String Functions
+
+The Poke standard library provides the following functions to do
+work on strings:
+
+@menu
+* ltrim::              Remove leading whitespace.
+* rtrim::              Remove trailing whitespace.
+@end menu
+
+@node ltrim
+@section ltrim
+
+The standard function @code{ltrim} provides the following interface:
+
+@example
+defun ltrim = (string s) string: @{ ... @}
+@end example
+
+It returns a copy of the input string @code{s} with any leading whitespace 
removed.
+
+@node rtrim
+@section rtrim
+
+The standard function @code{rtrim} provides the following interface:
+
+@example
+defun rtrim = (string s) string: @{ ... @}
+@end example
+
+It returns a copy of the input string @code{s} with any trailing whitespace 
removed.
+
 @node Sorting Functions
 @chapter Sorting Functions
 
diff --git a/src/std.pk b/src/std.pk
index 414a065..075bfb1 100644
--- a/src/std.pk
+++ b/src/std.pk
@@ -60,6 +60,33 @@ defun catos = (char[] chars) string:
    return s;
   }
 
+  /* Return S with leading whitespace omitted.  */
+defun ltrim = (string s) string:
+  {
+    defvar result = "";
+    for (c in s)
+      {
+       if ((c != ' ' && c != '\t') || result != "")
+         result = result + c as string;
+      }
+    return result;
+  }
+
+  /* Return S with trailing whitespace omitted.  */
+defun rtrim = (string s) string:
+  {
+    defvar result = "";
+    defvar i = s'length;
+    while (i > 0)
+    {
+      defvar c = s[i - 1];
+      if ((c != ' ' && c != '\t') || result != "")
+        result = c as string + result;
+      i = i - 1;
+    }
+    return result;
+  }
+
 defun atoi = (string s, int b = 10) long:
   {
     defvar result = 0;
diff --git a/testsuite/poke.std/ltrim.pk b/testsuite/poke.std/ltrim.pk
new file mode 100644
index 0000000..1a08c0a
--- /dev/null
+++ b/testsuite/poke.std/ltrim.pk
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+
+/* { dg-command { ltrim ("  a string to trim  ") } } */
+/* { dg-output "a string to trim  " } */
diff --git a/testsuite/poke.std/rtrim.pk b/testsuite/poke.std/rtrim.pk
new file mode 100644
index 0000000..b62bf61
--- /dev/null
+++ b/testsuite/poke.std/rtrim.pk
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+
+/* { dg-command { rtrim ("  a string to trim  ") } } */
+/* { dg-output "  a string to trim" } */
-- 
2.11.0