feat(library): add experimental string IS_NUM function

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

6 files changed, 33 insertions, 0 deletions

diff --git a/pseudocode-lib/README.md b/pseudocode-lib/README.md
index 90fab0e..9182b14 100644
--- a/pseudocode-lib/README.md
+++ b/pseudocode-lib/README.md
@@ -32,3 +32,5 @@ The library provides `&`, `_EXP_STRING_NUM_TO_STR` (INTEGER/REAL), `_EXP_STRING_
 `_EXP_STRING_ASC(S : _EXP_STRING)` returns the unsigned code of the first byte as INTEGER, or 0 for an empty string. Its `(Ch : CHAR)` overload returns the unsigned byte code of Ch. For ASCII characters this is the ASCII code.
 
 `_EXP_STRING_CHR(Code : INTEGER)` returns a new `_EXP_STRING` containing the low eight bits of Code as one byte. Unlike built-in STRING, `_EXP_STRING` preserves NUL: `_EXP_STRING_CHR(0)` has length 1.
+
+`_EXP_STRING_IS_NUM(S : _EXP_STRING)` returns BOOLEAN indicating whether a nonempty string is fully consumed by `strtod`. Leading whitespace is accepted; trailing whitespace, other trailing text, and embedded NUL bytes are rejected. Invalid numeric text returns FALSE without throwing.
diff --git a/pseudocode-lib/_exp_string.cc b/pseudocode-lib/_exp_string.cc
index ae53ac1..4cfd650 100644
--- a/pseudocode-lib/_exp_string.cc
+++ b/pseudocode-lib/_exp_string.cc
@@ -1,6 +1,7 @@
 #include <algorithm>
 #include <cctype>
 #include <cstdio>
+#include <cstdlib>
 #include <exception>
 #include <stdexcept>
 #include <string>
@@ -127,6 +128,14 @@ void _exp_string_impl_chr(void *Target, long long Code) {
         text(Target).assign(1, static_cast<char>(static_cast<unsigned char>(Code)));
     });
 }
+int _exp_string_impl_is_num(void *Handle) {
+    return checked([&]() -> int {
+        const auto &Source = text(Handle);
+        char *End = nullptr;
+        std::strtod(Source.c_str(), &End);
+        return !Source.empty() && End == Source.c_str() + Source.size();
+    });
+}
 void _exp_string_impl_output(void *Handle) {
     checked([&] {
         const auto &Text = text(Handle);
diff --git a/pseudocode-lib/_exp_string.cps b/pseudocode-lib/_exp_string.cps
index 965a251..975a583 100644
--- a/pseudocode-lib/_exp_string.cps
+++ b/pseudocode-lib/_exp_string.cps
@@ -24,6 +24,7 @@ EXTERN "C" EXTERN_FUNCTION _exp_string_impl_ucase_char(C_CHAR) RETURNS C_CHAR
 EXTERN "C" EXTERN_FUNCTION _exp_string_impl_asc(_EXP_STRING_HANDLE) RETURNS _EXP_STRING_C_INTEGER
 EXTERN "C" EXTERN_FUNCTION _exp_string_impl_asc_char(C_CHAR) RETURNS _EXP_STRING_C_INTEGER
 EXTERN "C" EXTERN_PROCEDURE _exp_string_impl_chr(_EXP_STRING_HANDLE, _EXP_STRING_C_INTEGER)
+EXTERN "C" EXTERN_FUNCTION _exp_string_impl_is_num(_EXP_STRING_HANDLE) RETURNS C_INT
 EXTERN "C" EXTERN_PROCEDURE _exp_string_impl_output(_EXP_STRING_HANDLE)
 
 CLASS _EXP_STRING
@@ -117,3 +118,6 @@ FUNCTION _EXP_STRING_CHR(Code : INTEGER) RETURNS _EXP_STRING
     CALL _exp_string_impl_chr(Result._HANDLE, (_EXP_STRING_C_INTEGER)Code)
     RETURN Result
 ENDFUNCTION
+FUNCTION _EXP_STRING_IS_NUM(S : _EXP_STRING) RETURNS BOOLEAN
+    RETURN (BOOLEAN)_exp_string_impl_is_num(S._HANDLE)
+ENDFUNCTION
diff --git a/tests/library/exp-string/expected.txt b/tests/library/exp-string/expected.txt
index 0680cf2..030a4c2 100644
--- a/tests/library/exp-string/expected.txt
+++ b/tests/library/exp-string/expected.txt
@@ -39,3 +39,6 @@ AZ
 65
 1:0
 65:255
+TRUE:FALSE:FALSE
+TRUE:FALSE:FALSE
+FALSE:FALSE
diff --git a/tests/library/exp-string/notes.md b/tests/library/exp-string/notes.md
index 7eddda1..e2a1bbc 100644
--- a/tests/library/exp-string/notes.md
+++ b/tests/library/exp-string/notes.md
@@ -19,3 +19,5 @@ UCASE converts AbC@19 to ABC@19 without modifying the source. Its CHAR overload
 ASC returns 65 for CHAR A and the first byte of ABCDEFGH, zero for empty strings or NUL, and 255 for a byte with all eight bits set. These byte-code functions are compiler/library extensions.
 
 CHR codes 65 and 90 concatenate to AZ; converting A to a code and back preserves 65. Code zero produces one retained NUL byte. Taking the low eight bits gives 65 for 321 and 255 for -1.
+
+IS_NUM accepts 12.5 and a leading space before 12.5. It rejects trailing junk, empty input, trailing space, whitespace alone, and a NUL byte before or after a valid number, without throwing. Numeric recognition follows the compiler's strtod-based extension.
diff --git a/tests/library/exp-string/program.cps b/tests/library/exp-string/program.cps
index e789e54..0adf86c 100644
--- a/tests/library/exp-string/program.cps
+++ b/tests/library/exp-string/program.cps
@@ -46,6 +46,7 @@ CALL CheckLCase()
 CALL CheckUCase()
 CALL CheckAsc()
 CALL CheckChr()
+CALL CheckIsNum()
 
 PROCEDURE CheckLeft()
     DECLARE Letters : _EXP_STRING((C_STRING)"ABCDEFGH")
@@ -123,3 +124,15 @@ PROCEDURE CheckChr()
     OUTPUT _EXP_STRING_LENGTH(_EXP_STRING_CHR(0)), ":", _EXP_STRING_ASC(_EXP_STRING_CHR(0))
     OUTPUT _EXP_STRING_ASC(_EXP_STRING_CHR(321)), ":", _EXP_STRING_ASC(_EXP_STRING_CHR(-1))
 ENDPROCEDURE
+
+PROCEDURE CheckIsNum()
+    DECLARE Number : _EXP_STRING((C_STRING)"12.5")
+    DECLARE Junk : _EXP_STRING((C_STRING)"12x")
+    DECLARE Empty : _EXP_STRING
+    DECLARE Leading : _EXP_STRING((C_STRING)" 12.5")
+    DECLARE Trailing : _EXP_STRING((C_STRING)"12.5 ")
+    DECLARE Whitespace : _EXP_STRING((C_STRING)" ")
+    OUTPUT _EXP_STRING_IS_NUM(Number), ":", _EXP_STRING_IS_NUM(Junk), ":", _EXP_STRING_IS_NUM(Empty)
+    OUTPUT _EXP_STRING_IS_NUM(Leading), ":", _EXP_STRING_IS_NUM(Trailing), ":", _EXP_STRING_IS_NUM(Whitespace)
+    OUTPUT _EXP_STRING_IS_NUM(Number & _EXP_STRING_CHR(0)), ":", _EXP_STRING_IS_NUM(_EXP_STRING_CHR(0) & Number)
+ENDPROCEDURE